Go to the people,
live among them,
learn from them,
plan with them,
work with them.
Start with what they know,
build on what they have.
But with the best leaders,
when the work is done,
the task accomplished,
the people will say,
"We have done this
ourselves."
Credo
International Movement
for Rural Reconstruction
ENVIRONMENTALLY SOUND
SMALL-SCALE
AGRICULTURAL PROJECTS
GUIDELINES FOR PLANNING
Revised Edition Prepared
By
Miguel Altieri
University of California,
Berkeley
Edited
By
Helen L. Vukasin
CODEL, Inc.
CODEL, Inc. (Coordination in
Development)
VITA (Volunteers in Technical Assistance)
CODEL, Inc.
Environment and Development
Program
475 Riverside Drive,
Room 1842
New York, New York 10115,
U.S.A.
Order books from:
VITA
1600 Wilson Boulevard,
Suite 500
Arlington, Virginia
22209 USA
Tel:
703/276-1800 * Fax:
703/243-1865
Internet:
pr-info@vita.org
Permission received to
reprint as follows.
(See Appendix A for
citations.)
International Council for Research on
Agroforestry, page 129-134
MacMillan Publishing
Company, page 76
Mujeres en Desarrollo,
page 121
Praeger Publishers,
page 124
Prentice-Hall, Inc.,
page 104
Westview Press,
page 17
Worldwide Neighbors,
page 138
VITA, page 34,
126
Drawings by Linda
Jacobs
Diagrams by Linda
Schmidt
Cover Design by Susann Foster Brown
CODEL 1990
ISBN No.
0-86619-283-2
TABLE OF CONTENTS
PART I:
INTRODUCTION
Chapter 1 -
USERS AND USES
The Purposes
of the Manual
Who Should
Use This Manual
What the
Manual Provides
Chapter 2 -
THE RELATION OF AGRICULTURE
AND
ENVIRONMENT
What Is Meant
By Ecology and Environment
How
Agriculture and Environment Are Related
Why
Ecological Concepts Are Important for Agricultural Development
What
Ecosystems Are and Why They Are Important
What Happens
When Natural Systems Are Altered
The Food Web
How Stability
Relates to Diversity
Succession
and Agroecosystems
Limiting
Factors
How Knowledge
of Environmental Concepts and Impacts
Can Be Used to Ensure More Successful
Projects
PART II:
PLANNING FOR
SUSTAINABLE AGRICULTURE
Chapter 3 -
THE PLANNING PROCESS
Who
Plans
The End is
the Beginning
Flexible
Planning
1.
Identify and Assess Needs and
Constraints
2.
Community Profile and Natural Resource
Profile
Community Profile
Natural Resource Profile or Inventory
Learning from Local Agricultural
Experience
Agricultural Practices
Soil
Water
Climate
Land Tenure
3.
Define Goals and Objectives
4.
Design Project with Consideration of
Trade-Offs
5.
Implement the Activity
Training Programs
Funding
6.
Monitor the Project
7.
Evaluate the Project
A Summary
Checklist
Chapter 4 -
OTHER CONSIDERATIONS FOR PLANNING
Introduction
Legal
Considerations
Socio-Cultural
Considerations
Women and
Agriculture
Economic
Considerations
PART III:
BACKGROUND FOR PLANNING
Chapter 5 -
SOIL MANAGEMENT THROUGH
REDUCTION OF
EROSION
Erosion:
What Is It?
Sheet Erosion
Rill Erosion
Gully Erosion
Laterite Formation
Soil
Loss
Erosion By
Wind Action
Soil Cover
and Why It Is Important for Control of Erosion
How Erosion
Can Be Controlled
How Plant
Residues Combat Erosion
Improved
Tillage Methods for Erosion Control
Reduced Tillage
Conservation Tillage
No-Till
Crop Rotation
and Erosion Control
Some Support
Practices for Erosion Control
Contouring
Contour Strip Cropping
Terracing
The Effects
of Soil Management/Erosion Control
Some
Alternatives
Summary of
Erosion Control Practices
Chapter 6 -
WATER SUPPLY AND MANAGEMENT
The Major
Sources of Water
Surface Water
Rain
Groundwater
The Water
Balance in Croplands
How Water
Moves and the Effects
Physical Transport
Chemical Transport
The
Importance of Irrigated Agriculture
Why It Is
Necessary to Plan Irrigation
Projects Carefully
Using Surface
Water for Irrigation
Effect on the Aquatic Environment
Effect on Farmland
Salinization and Alkalinization
Salinization
Alkalinization
Using
Groundwater for Irrigation
Irrigation
Return Flows and Their Effects
Irrigation
and Human Health
Determining
the Effects of Water Supply and Management Projects
What
Alternatives Exist
Chapter 7 -
SOIL NUTRIENT MANAGEMENT
Sources of
Plant Nutrients
Natural Soil Fertility
Organic Matter
The Significance of the C/N Ratio
Plant Residues
Animal Wastes
Legumes
Precipitation and Run-on Water
Inorganic Fertilizers
Evaluating
the Source of Nutrients
Composting
The Effects
of Fertilizers on the Environment
Leaching
Runoff
Erosion
The Effects
of Movement or Loss of Soil Nutrients
Eutrophication
Health Effects
Nitrites
Nitrates
Ammonia
Phosphorus
Management of
Nutrient-Related Factors
Managing Fertilization
Crop Rotations
Animal Wastes
Plowing-Under Green Legumes
Controlling Surface Applications
The Effects
of Nutrient Management
Alternatives
for Nutrient Control
Chapter 8 -
PEST MANAGEMENT
Environmentally
Sound Pest Management Practices
Alternatives
to Pesticides
Local Plants
Crop Management Practices
Rotation
Resistant Varieties
Intercropping
Planting Time
Planting Space
Destruction of Alternate Host Plants
Mechanical and Traditional Control
Practices
Biological Control Methods
Integrated
Pest Management: What Is It?
Definition of
a Pesticide
Effects of
Pesticide Use
Effects on People
Effects on Soil Fertility
Effects of Pesticides on the Balance of
Nature
Some Other Effects of Pesticides
Effects on the Aquatic Environment
Pesticide Persistence
How
Pesticides Move About the Environment
Pesticide Pathways
Distribution in Soil
Distribution in Water
Some Factors
That Should Be Considered Before Applying Pesticides
Local Experience
Alternative Pest Control Measures
Synergism
Timing of Application
Pesticide Movement
Precautions Necessary
Checklist for
Projecting the Impacts of Chemical
Pesticide Use and the Potential For
Alternatives
Chapter 9 -
AGROFORESTRY SYSTEMS
Definition
and Classification
Structure
Function
Ecologic or Climatic
Socio-Economic Scale and Level of
Management
Some
Advantages of Agroforestry Systems
Ecological Advantages
Economic and Socio-Economic Advantages
Some
Constraints of Agroforestry Systems
Role of Women
in Agroforestry
The Role and
Effect of Trees
Examples of
Traditional Agroforestry Systems
Design of
Agroforestry Combinations
1.
Alley Cropping in High Potential Areas
2.
Contour Planting
3.
Fodder Bank - Cut and Carry
4. Fodder Bank - Grazing
5.
Fruit Improvement
6.
Hedges/Living Fences
7.
Mixed Intercropping
8.
Multistorey Planting of Domestic/Industrial Tree Crops
9.
Tree Planting Around Water Places and Dams
10.
Selective Clearing
11.
Woodlot Planting for Fuelwood and Poles
PART IV:
CONCLUSION
Chapter 10 -
CONCLUSION: A CHECKLIST FOR
SUSTAINABLE
DEVELOPMENT, EXAMPLES OF
TRADITIONAL
SYSTEMS, AND LONG TERM
EVALUATION
A Checklist
for Developing Sustainable Agricultural Projects
Examples of
Traditional Resource Management Systems
Long Term
Evaluation of Local Agro-Ecosystems
Additional
Assistance or Information
Appendix A -
REFERENCES
Appendix B -
Appendix C -
GLOSSARY
PREFACE
The
original manuscript for this manual was a creative idea that
developed
during a conference in 1977, sponsored by the Mohonk
Preserve,
that brought together the US environmental nongovernmental
organizations
(NGOs) with those groups that work with
development
assistance in the Third World. Peter
Freeman, Robert
Tillman and
Ann LaBastille created a document that provided the
basis for the
original edition. Paul and Marilyn
Chakroff worked on
a subsequent
draft and Laurel Drubin, formerly with VITA, and
CODEL staff
edited the manuscript for publication in 1979.
Since
that time
CODEL has published four additional volumes on forestry,
water,
energy, and livestock. Each volume has
relied heavily on
input from
technical experts and potential users in the field.
The revised edition of the agriculture
manual is indebted to
many persons
for constructive and helpful comments on a review
draft
prepared by Miguel Altieri. CODEL
acknowledges with thanks
contributions
from the following:
Ms. Becky Andrews, Rodale Press,
Pennsylvania
Mr. William R. Austin, Van Wingerden
International, Inc.,
North Carolina
Mr. Fabio Bedini, Undugu Society of
Kenya, Kenya
Ms. Joan Brinch, Kenya Institute of
Organic Farming, Kenya
Mr. Richard Carpenter, East-West Center,
Environment and
Policy Institute, Hawaii
Professor Gordon R. Conway,
International Institute for Environment
and Development, England
Ms. Margaret Crouch, Volunteers in
Technical Assistance,
Washington, D.C.
Professor Peter F. Ffolliott, University
of Arizona, Arizona
Mr. Peter Freeman, Development Ecology
Information Service,
Washington, D. C.
Mr. George Gerardi, Hermandad, Dominican
Republic
Mr. Terry Gips, International Alliance
for Sustainable Agriculture,
Minnesota
Mr. Matthias Quepin, Kenya Institute of
Organic Farming,
Kenya
Mr. Lawrence Hamilton, East-West Center,
Environment and
Policy Institute, Hawaii
Ms. Susanna B. Hecht, University of
California at Los Angeles,
California
Mr. John Michael Kramer, CARE, New York
Dr. Bede N. Okigbo, International
Institute of Tropical Agriculture,
Nigeria
Rev. John Ostdiek, OFM, Franciscan
Missionary Union,
Tennessee
Mr. W.J. Pape, Swaziland Farmer
Development Foundation,
Swaziland
Ms. Caroline Pezzullo, Pezzullo
Associates, New York
Mr. Coen Reijntjes, Information centre
for Low External Input
Agriculture, The Netherlands
Mr. Raniari Sabatucci, Kenya Freedom
from Hunger Council,
Kenya
Rev. Kenneth F. Thesing, MM, Maryknoll,
New York
Dr. Norman Ulsaker, Institute for
Alternative Agriculture,
Maryland
Mr. Napoleon T. Vergara, Participatory
Forestry Development
Through Extension, FAO Thailand
Mr. Peter von der Lippe, Christian
Children's Fund, Virginia
Mr. Fred R. Weber, International
Resources Development and
Conservation Services, Idaho
Bro. Andrew Winka, Christian Brothers
Conference, New York
Mr. Ben Wisner, Hamshire College,
Massachusetts
Dr. Timothy Wood, Wright State
University, Ohio
Mr. Charles S. Wortmann, CIAT Regional
Bean Programme of
Eastern Africa, Uganda
Miguel Altieri, with assistance from Helen
L. Vukasin, CODEL
Environment
and Development Program, spent many hours integrating
the useful
technical and user suggestions in order to make the
text more
useful to the field staff to which it is addressed.
In addition to the above named persons
there are some special
acknowledgments
that should be mentioned. International
students
in a forestry
class at the University of Arizona each wrote extensive
comments on
the Agroforestry chapter that provided useful local
examples and
perspectives. Terry Gips, author of the
newly published
book,
Breaking the Pesticide Habit, commented helpfully on the
Pest
Management chapter. The candid comments
of colleagues in
Africa have
helped to reduce the Northern perspective of the text.
Finally, a special word of gratitude is
due to Debra Decker who
contributed
her talents to the preparation of the text for printing
with
dedication - from the initial draft of the author through all the
subsequent
changes.
We welcome comments from readers of the
book. A questionnaire
is enclosed
for your convenience. Please share your
reactions.
Rev. Boyd Lowry, Executive Director
Sr. Mary Ann Smith, Environment &
Development Program
ABOUT CODEL
Coordination
in Development (CODEL) is a private, not-for-profit
consortium of
forty Christian-related development agencies working
in developing
countries. CODEL funds community
development activities
that are
locally initiated and implemented.
These activities
include
agriculture, water, forestry, health, appropriate technology,
and training
projects.
The
Environment and Development Program of CODEL serves the
private and
voluntary development community by providing workshops,
information,
and materials designed to document the urgency,
feasibility,
and potential of an approach to small-scale development
that stresses
the interdependence with human and natural resources.
This manual
is one of several materials developed under the Program
to assist
development workers in taking the physical environment
into account
during project planning, implementation, and
evaluation.
For more information, contact CODEL,
Environment and
Development
Program at 475 Riverside Drive, Room 1842, New York,
New York
10115 USA.
ABOUT VITA
Volunteers in
Technical Assistance (VITA) is a private non-profit
international
development organization. It makes
available to
individuals
and groups in developing countries a variety of information
and technical
resources aimed at fostering self-sufficiency:
needs
assessment
and program development support; by-mail and on-site
consulting
services; information systems training; and management of
fields
projects. VITA promotes the use of
appropriate small-scale
technologies,
especially in the area of renewable energy.
VITA's
extensive
documentation center and worldwide roster of volunteer
technical
experts enable it to respond to thousands of technical
inquiries
each year. It also publishes a
quarterly magazine and a
variety of
technical manuals and bulletins. For
more information,
contact VITA
at 1815 N. Lynn Street, Suite 200, Arlington, Virginia
22209 USA.
PART I:
INTRODUCTION
CHAPTER 1
USERS AND USES
THE PURPOSES OF THE MANUAL
This manual is designed to assist those
who plan and implement
small-scale
agricultural projects. By promoting
awareness of
environmental
concerns, the manual can increase the development
worker's
ability to design projects that are both environmentally
sound and
potentially more sustainable.
This manual has two objectives:
1.
To promote well-planned and environmentally sound small-scale
agricultural projects.
2.
To introduce environmental concepts into technology development
and alternative management techniques,
and encourage
the transfer into training programs.
Environmentally sound planning requires
more than finding the
right
technology and a source of funds.
Planning involves consideration
of the
social, cultural, economic, and natural environments in
which the
project occurs. The challenge is to
develop sustainable
food systems
that have reasonable production but do not degrade the
resource-base
and upset the ecological balance.
Development workers
are in a
position to pass on awareness of environmental concerns to
community
groups, government planners, village residents, farmers,
and
students. For example, a development
worker may use this
manual in a
training course to increase students' awareness of erosion
control
methods and alternatives. As a project
planner or implementor,
a development
worker may wish to use the book for planning
or on-the-job
training of project workers or for technical training
of farmers
and local residents.
By providing guidelines to planning, this
manual can assist
development
workers to view projects as part of larger environmental
systems.
It offers a perspective that can assist
users to ask the
right
questions and to look for and find information about local
resource
availability and use, traditional methods, weather patterns,
social, and
cultural traditions.
Many issues of importance to small-scale
agricultural projects
that need to
be considered are beyond the scope of this manual.
These
include: land use patterns; inability of small landless farmers
to take
risks; lack of credit and money; and access to technical
personnel and
appropriate agricultural expertise.
Finally, this
manual cannot
address all of the environmental conditions or implications
associated
with individual project sites. The use
of the
general
concepts and principles outlined here should enable development
workers to
recognize environmental issues and to consider
them in the
planning process.
WHO SHOULD USE THIS MANUAL
This manual has been prepared for those
who are actively
engaged in
planning and implementing small-scale agricultural
projects.
It will be most useful for those who wish
to:
- learn more about environmental
considerations and their
relationship to small-scale agricultural
projects
- approach agricultural projects, even
though small, from an
environmentally aware perspective
through the promotion of
technologies appropriate to the
situation
- integrate environmental and
socio-economic factors into
agricultural planning activities, so
that recommended technologies
fit the resource base, perceptions, and
needs of local
farmers.
WHAT THE MANUAL PROVIDES
The manual covers the following subjects:
* Introduction to important ecological
concepts relevant to the
development of agricultural projects.
* Technical information related to
environmental issues.
* Some suggestions for planning
small-scale agricultural
projects.
* Guidelines for using knowledge of
environmental effects to
determine positive (benefits) and
negative (costs) factors in a
given small-scale agricultural effort.
Consideration of these factors can lead to
well-informed decisions
on
alternative project designs. In
addition, this background
information
can be used as the basis for planning environmentally
sound
projects in the areas of water supply and management, nutrient
management,
soil conservation, pest management, and related
subjects.
CHAPTER 2
THE RELATION OF AGRICULTURE
AND ENVIRONMENT
Agriculture is defined as the science,
business, and art of growing
crops and
rearing animals in order to produce food, fodder, fiber,
and other
products useful to people. A customary
goal of agricultural
projects is
to enhance food production for growing populations.
Such projects
should also be concerned with the farm as a
multiple-use
system that includes animals and plants other than food
crops.
However, this manual emphasizes crop
production. Other
volumes in
the series deal with livestock, forestry, water, and energy.
Crop production can be increased by one or
more of the following:
- expanding the area planted to crops
- increasing the yield per unit area of
individual crops
- growing more crops per year (in time
and/or space) on the
same unit of land
<MODIFICATION
OF THE NATURAL SYSTEM RELATED TO ENERGY SUBSIDY AND STABILITY>
03p04y.gif (600x600)
03p04z.gif (486x486)
Agriculture
is essentially an environmental activity.
It is a process
of adapting
the natural ecosystem in order to channel energy to
people in the
form of food. The process works by
modifying the
environment
by the addition of energy and resources.
The greater
the degree of
modification of the natural system, the more energy
can be
channeled to humans. At the same time,
modification may
also decrease
the stability and sustainability of the system.
(Altieri
2.1)
Agricultural systems that have greatly
modified the natural
system are
thus dependent on high energy and resource inputs to
achieve and
maintain a desired level of yield. In
the tropics commercial
cash crops
(monocultures) and tree-based plantations require
more human
intervention than annual multi-crops (polycultures) and
combinations
of ground and tree crops (agroforestry systems).
<EFFECTS
OF MODIFYING THE NATURAL ECOSYSTEM>
03p05y.gif (540x540)
03p05z.gif (600x600)
Systems that require more input and
intervention are usually
associated
with higher resource depletion and negative social impacts
than
low-input, diversified agricultural systems.
Modification, however,
also implies
the possibility of enhancing the environment for
humans in
addition to the negative impact on the environment
resulting
from altering the natural system. The
fundamental objective
of
agricultural development should be to balance these two
possibilities
in the search for environmentally sound and socially
acceptable
agricultural production techniques.
Environmental problems in some areas have
developed because
of the
misapplication of temperate-zone technologies to the tropics.
Sustaining
yields in these areas will only be achieved through
farming
methods unique to the ecological and socio-economic conditions
of the
tropics. (Dover and Talbot 2.5)
WHAT IS MEANT BY ECOLOGY AND
ENVIRONMENT
Many environmental concepts have their
basis in the science of
ecology.
Ecology is defined as the study of the
structure and function
of nature, or
the interactions among and between the living and
non-living
components of the place being studied.
Ecology, then,
includes
aspects of the sciences of biology, physiology, geology,
chemistry, meteorology,
and others in the study of natural systems
or
ecosystems.
In agriculture, the appropriate level of
organization to be
studied and
managed is the agroecosystem and the corresponding
discipline is
agroecology. All that ecologists
study--such as the
distribution,
abundance, and interactions between organisms and
within the
physical environment, succession, and the flows of energy
and
materials--are important for an understanding of agroecosystems.
These
ecological processes can shed light on the development of
sustainable
agricultural technologies. In
agricultural studies, the
social
sciences also are critical in understanding the relation between
natural and
social systems. (Altieri 2.1, King 2.6)
Environment, on the other hand, defines
the natural, social,
cultural, and
economic surroundings of a project.
Agricultural
projects
influence and are influenced by environmental factors.
HOW
AGRICULTURE AND ENVIRONMENT ARE RELATED
Each agricultural project takes place
within a complex system
of social
attitudes, cultural framework and practices, economic
structures,
and physical, chemical, and biological factors.
This total
system is the
environment in which a project occurs, and every
agricultural
project, no matter what its size or scope, affects and is
affected by
these factors, i.e., by its environment.
The many forms
of
agriculture found throughout the world are the result of variations
in local
climate, soil, economics, social structure, and history.
Water
availability,
solar radiation, temperature, and soil conditions are the
main
determinants of the physical ability of crops to grow and
farming
systems to exist. Human factors that
play dominant roles
include
social, economic, and political considerations.
Among these
are:
traditional and religious practices; cost and ease of transport;
existence of
marketing channels; inflationary tendencies; availability
of capital
and credit; and stability of the government, accompanied
by continuity
and consistency in policies, programs, and commitment.
In other
words the environment of any one area consists of the
biosphere in
the area, including the time, customs, and practices of
the
people. (Briggs and Courtney 2.2)
Farming systems also depend heavily on the
character of
production,
i.e., whether the crops are produced in a subsistence or a
commercial
economy. The subsistence farmer
produces crops primarily
for family
consumption. Consequently, there may be
resistance to
change in
production methods because livelihood and survival are
threatened if
the changes turn out to be unproductive.
Commercial
farmers,
subject to market conditions, may also resist change because
they are not
willing to take the risk or because they are not willing
to sacrifice
short-term gains.
The way crops are grown further depends on
the availability
and level of
technology, the availability of suitable land area, and
other
resources. High levels of technology
and large land units are
generally
accompanied by a high degree of mechanization, and
uniformity of
land, soil fertility, and genotype. On
the other hand
low levels of
technology and small parcels of land are usually associated
with varying
soils, intensive cropping systems, and less
mechanization.
<RELATION
BETWEEN AGROECOSYSTEMS AND SOCIAL FACTORS>
03p08y.gif (600x600)
03p08z.gif (540x540)
All agricultural development projects,
whether they involve
irrigation,
pest control, fertilization, or the introduction of new
varieties of
crops and cropping methods, have positive and negative
effects upon
the environment.
Some of the interactions between parts of
the total environment
can be easily
forecast. For example, it is clear that
the
amount of
rainfall, the money available for the project, and the
involvement
in the project of local people are factors that can affect
the success
of an agricultural project. Other
factors, however, such
as the effect
of using certain pesticides over a long period of time are
much harder
to predict.
Environment in the agricultural setting
has been defined here
to include
the people of the region, the animals, the plants, soil,
water,
nutrients, the weather, ways of planting and cultivating, and
so on.
Those planning and implementing small-scale
projects must
consider all
of these influences. Interactions
between agroecosystems
and social
systems involve exchanges of energy, materials, and
information
between both systems. The decisions
that farmers make
in using a
cropping system or technology depend not only on the
technology
and local resources available but numerous aspects of the
surrounding
social system as well.
WHY ECOLOGICAL CONCEPTS ARE
IMPORTANT
FOR AGRICULTURAL DEVELOPMENT
Agricultural development implies
continuing change in the
system toward
an improved system. Therefore, in order
for development
to occur as a
result of agricultural project activities, the alterations
or changes
made as a result of the project must have more
positive
effects than negative. Because they are
principles explaining
how
ecosystems function, ecological concepts can provide assistance
with judging
how the natural environment may be affected by
agricultural
projects. Moreover, understanding the
ecological
mechanisms
that underlie basic processes in natural ecosystems
(such as
nutrient cycling, succession, and others), can provide important
information
for developing appropriate low input alternatives for
soil
management, pest and disease management, development of
technologies
for various activities from planting to post-harvest
phase, and
other needs.
WHAT ECOSYSTEMS ARE AND
WHY THEY ARE IMPORTANT
A planner viewing a potential project site
is looking at an
ecological or
natural system--an ecosystem. An
ecosystem is defined
as the
complex of organisms interacting among themselves and with
the
non-living environment in processes such as competition, predation,
decomposition,
feeding, habitat, and so on. The
structure of the
ecosystem is
related to species diversity. The more
complex the
structure the
greater the diversity of species. The
function of the
ecosystem is
related to the flow of energy and the cycling of materials
through the
structure. The relative amount of
energy needed to
maintain the
system depends upon its structure. The
more complex
and mature it
is, the less energy it needs to maintain the structure.
When an
agricultural project interferes with the flow of energy
and/or
materials through the natural system or ecosystem by adding
fertilizers
or eradicating pests, ecological patterns may be changed.
Whether an area is farmland under rice
cultivation for many
years, or a
virgin forest, it is a functioning system.
Any decision
made to
introduce change, such as replacing the rice with a new crop
or cutting
down the forest for agriculture, should be made with an
awareness of
the characteristics of the existing system and of the
potential
effects such a decision would have.
A good example is the substitution of
tractor for buffalo power
in rice
fields of Sri Lanka. At first sight,
the substitution of tractor
for buffalo
seems to involve a straightforward trade-off between more
timely
planting and labor saving, on the one hand, and the provision
of milk and
manure, on the other. But associated
with buffaloes are
buffalo
wallows and these in turn provide a surprising number of
benefits.
In the dry season these mud holes are a
refuge for fish
who then move
back to the rice fields in the rainy season.
Some
fish are
caught and eaten by the farmers and by the landless,
providing
valuable protein; other fish eat the larvae of mosquitoes
that carry
malaria. The thickets harbor snakes
that eat rats that
eat rice, and
lizards that eat the crabs that make destructive holes
in the
ricebunds. The wallows are also used by
the villagers to soak
coconut
fronds in preparation for thatching. If
the wallows are lost
because of
mechanization, so are these benefits.
Moreover, the
adverse
consequences may not stop there. If
pesticides are brought
in to kill
the rats, crabs or mosquito larvae, then pollution or pesticide
resistance or
both can become a problem. Similarly if
tiles are
substituted
for the thatch this may hasten forest destruction since
firewood is
required to bake the tiles.
In forest ecosystems there are also
dynamic relationships
among the
components. Trees protect forest soils
by serving as
wind-breaks,
by breaking and cushioning the beating action of
raindrops so
that rainwater can be absorbed slowly and prevent
runoff.
Trees also provide shade and cooler
temperatures underneath
the tree
canopy. This protection of the soil
allows dead organic
matter to
decompose, releasing important nutrients used for growth
by the forest
plants. Forests also provide habitat
for wildlife and
certain trees
produce valuable fuelwood, construction materials, and
medicinal
substances--all resources used by local farmers.
When a
development
worker makes the decision to assist the farmer to
increase
yields by substituting another crop for rice or cutting down
all or part
of the forest, it is also a decision about interacting with
the
ecosystem. For that reason the
environmental ramifications
should be
taken into account.
WHAT HAPPENS WHEN NATURAL SYSTEMS
ARE ALTERED
A look at the forest ecosystem will show
what can happen
03p12y.gif (486x486)
03p12z.gif (486x486)
when the
protection of the trees is taken away and not replaced by
other cover:
* Wind can pick up the organic matter and
dry out the soil so
that it is not good for cultivation.
* Nutrient-rich soil particles may be dislodged
by raindrops
during rain storms.
Both soil particles and nutrients in
solution may be carried away.
* Protection against flooding may
disappear. Forests maintain
soil porosity, aid the infiltration of
rain, and retard the
surface movement of water, thereby
protecting villages from
floods and retaining moisture in the
soil.
* Sources of firewood, lumber, and tree
crops for domestic
needs are no longer available.
* Diversity of plant and animal life is
affected. Many birds,
mammals, reptiles, amphibians, and
insects that prey upon
agricultural pests disappear with the
loss of the forest
habitat.
The Food Web
Plants, plant-eating animals, predators,
scavengers and decomposers
interact in
what is commonly called a "food web."
Through
03p13.gif (486x486)
the food web,
food energy moves in one direction:
from producers to
consumers.
With a knowledge of the dynamics of the
food web, the quantity
of food
available to us can be increased by:
- reducing the number of organisms that
compete for the same
food
- converting forests and rangelands into
cropland
- increasing the efficiency of food use by
livestock by improving
animal husbandry practices
- growing crops that put more
photosynthetic energy into
edible parts
- eating less meat and more fruits,
vegetables, and cereals
All these efforts are limited by the
energy inefficiencies that are
inherent in
food webs, since there is energy lost at each transfer
from one
trophic level to another trophic level.
HOW STABILITY RELATES TO
DIVERSITY
When land is cleared for agricultural
crops, usually the numbers
and kinds of
plants and animals living there are greatly reduced.
It is often best
to design projects that will maintain the diversity
of the plants
and animals insofar as possible.
Ecological theory
holds that
diversity is often related to stability, implying that ecosystems
that contain
many different kinds of species are more stable
than those
containing only one (as in monoculture).
It is clear, however, from recent evidence
that agricultural
ecosystems
cannot be made more stable by simply increasing complexity.
Instead
biological interactions with potential stabilizing
effects must
be encouraged. For example, it is known
that diversification
of the
vegetational component of agroecosystems with
certain plant
associations often significantly lowers pest population,
even below
economic thresholds and result in agronomic benefits.
The challenge
is to evaluate which crop assemblages will result in
such
benefits.
For example, forest ecosystems tend to be
very diverse and
usually
stable. Severe stress on the physical
environment (e.g., by
drought) is
less likely to adversely affect such a system because
numerous
alternatives exist for the transfer of energy and nutrients
through the
system. Similarly, internal biological
or biotic controls
(such as
predator-prey relationships) prevent destructive shifts in
pest
population numbers. Hence, the system
is capable of adjusting
and
continuing to function with little if any detectable disruption.
Agricultural ecosystems, on the other
hand, (particularly those
that promote
the use of monoculture cropping systems) are likely to
be less
stable because a single species represents a high proportion
of the total
number of plants on the site. Such
systems, despite
their initial
high yields, carry with them the disadvantages characteristic
of new,
young, and developing ecosystems. Particularly,
they
are unable to
perform protective functions such as soil conservation,
nutrient
cycling, and population regulation. The
functioning of the
system
depends on continued human intervention in the form of
chemical
inputs, mechanization, and irrigation.
Nevertheless, monoculture
systems may
be easier to plant and less time-consuming to
tend, and
also lend themselves more readily to mechanization, use of
chemical
inputs, manipulation in various ways, and the advantages
ofeconomies
of scale. On the other hand, some
polyculture systems
developed by
small farmers throughout the Third World may also
require less
effort to tend. For example, corn,
bean, and cassava
crop
combinations in Costa Rica have been found to be less labor
demanding
because of reduced weed growth in the multi-crop fields.
<CROPPING
SYSTEMS>
03p14.gif (600x600)
<MONOCULTURES
COMPARED WITH POLYCULTURES>
03p15.gif (600x600)
One of the major reasons that small
farmers choose to use
multi-crop
systems (polycultures) is that frequently more yield can be
harvested from
a given area sown in polyculture than from an
equivalent
area sown in separate patches of a single crop (monoculture).
Over the long
term, single crop systems tend to be more
susceptible
to major crop failure than a multi-crop farm.
For example,
look at a
multi-crop farm containing equal numbers of pea,
maize (corn),
and bean plants compared with a monoculture maize
farm.
If both farms were attacked by a disease or
insect that
destroyed 80
per cent of the corn, the multi-crop farmer would still
have a 73 per
cent yield.
These considerations must be evaluated in
view of local situations,
therefore
small-scale experimentation is recommended whenever
farmers are
considering changing present crops or cropping
methods.
(Bunch 3.4)
SUCCESSION AND AGROECOSYSTEMS
Ecosystems tend toward complexity as they
approach maturity.
Immature
ecosystems are less diverse and have a high energy in-flow
per unit of
biomass. In mature ecosystems that are
more complex,
there is less
accumulation of energy because the energy flows
through more
diverse channels. This flow or change
is called succession.
Succession
refers to the process in which plant and animal
species enter
a site, change the site, and are later replaced by other
types of
plants and animals. The repeated
invasion and replacement
continues
until the site is dominated by types of plants and animals
that replace
themselves and are not forced out by other species.
The
final stage
is known as the "climax community" for the site.
The
climax species
will remain relatively unchanged until the site is disturbed
by fire,
changes in climate or water table, or by human
activities,
such as clearing land by logging or for farming.
(Cox and
Atkins 2.4)
<NATURAL
SUCCESSION>
The succession process can take hundreds
of years, but the
early stages
can be seen much more quickly. If a
field is left fallow
for one
growing season, weeds, legumes, grasses, and wildflowers will
invade the
field, along with various insects, rodents, and birds.
Left
alone for
many years, the field will eventually become a forest or
some other
climax community, but not necessarily similar to the
community
that previously existed on the site.
Succession may be
occurring
under different conditions than previously and produce a
different
climax. This makes conservation of
existing ecosystems
even more
important.
The observation and study of succession in
local natural ecosystems
has
apparently guided many traditional farmers in the design
and
structuring of their agricultural systems.
For example, farmers
in West Java
follow a system comprised of three stages--kebun, a
mixture of
annual crops; kebun-campuran incorporates some perennials;
and the
talun, a climax dominated by perennials, closely
mimicking the
successional sequence of neighboring tropical rainforests.
(Marten 2.7)
<STAGES OF
FARMING SYSTEM IN WEST JAVA>
03p17.gif (600x600)
Succession tends to restore agricultural
sites to the original
ecosystems--if
not prevented from doing so by the farmer.
To prevent
natural
succession, the farmer has to interfere with the process
continuously
by weeding (manually or by applying herbicides), or by
mulching or
flooding. In many cases, succession
would return a site
to forest,
secondary bush, woodland, or thicket vegetation within
decades, or
even years, thereby reversing negative effects of certain
activities
and induced changes in the environment.
Thus the impact
is
reversible. However, if a project has
had major impacts on the
site, such as
altering the water table or resulting in massive erosion
of topsoil,
natural succession can take centuries or may never return
the site to
its previous condition. The impact may
be irreversible.
For example,
sites exist where humans cleared out forests centuries
ago only to
have the unprotected site remain as a barren desert.
The
development worker should consider seriously the magnitude of
the project
and whether its effects are reversible or irreversible by
natural
processes.
In the well-known traditional practice of
slash and burn
agriculture,
farmers clear a patch of forest and burn the biomass to
release
nutrients before planting their crops.
Once the soil fertility
that was
built up over many years is exhausted by continuous
cropping, the
farmer moves to a new site and begins the cycle again.
On the
uncropped (fallow) land, succession takes over.
If enough
time is
allowed to elapse the land may again take on the characteristics
of the
original community and nutrients will be restored to the
soil.
Population growth and land tenure problems
have caused
fallow years
to be reduced or eliminated in many areas, thus, over
time
decreasing the soil fertility. Because
the decision to cultivate a
certain area
requires a continuous supply of nutrients, organic or
inorganic
fertilizers will have to be added to the site.
Inorganic
fertilizers
supply necessary chemical nutrients, but do not supply
organic
matter to the soil or contribute to the maintenance or improvement
of soil
structure over the long term. The use
of manure
and organic
fertilizer should be considered in the planning process
from the
beginning. Care should be taken that
sufficient nitrogen is
present,
which may have to be supplied by chemical sources.
In areas of Nigeria where the fallow
period has become progressively
shorter, an
improved fallow system was developed by the
International
Institute for Tropical Agriculture.
(See Appendix B for
address.)
Leguminous shrubs and trees (e.g., Leucaena
leucocephala)
are planted
in association with food crops to restore soil nutrients.
In these
"alley cropping systems" food crops are grown in rows (2-4
m. wide)
between strips of Leucaena which are pruned during
cropping.
The prunings provide green manure and mulch
for the
companion
crops, erosion control, fodder, firewood, and staking
material.
In a trial, Leucaena rows averaged 100-162
kg. of soil
nitrogen per
meter, increasing maize yields about 23 per cent.
It
has been
observed that Leucaena prunings are a more effective
nitrogen
source when incorporated in the soil than when applied as
mulch.
<ALLEY
CROPPING>
03p19.gif (600x600)
LIMITING FACTORS
Agricultural projects are undertaken in
all kinds of environments--forest,
flatland,
mountainside, or coastal plain. In each
area
there are
factors that will determine crop distribution and performance.
In some
agricultural projects, crop production can be improved
by increasing
or decreasing one factor. For example,
in a
given project
area, climate, nutrient availability, and soil type may
be perfect
for the growth of rice. However, there
is not enough
water for
rice plants to grow. In another field,
conditions may be
good for corn
but there is so much water the corn will drown.
In
both cases,
water availability is the limiting factor:
it dictates both
the type and
the quantity of growth on the site.
The physical environmental conditions of
an area--temperature
range,
amount, timing, and intensity of rainfall, soil characteristics,
and
availability of nutrients--dictate the variety and density of plant
and animal
species that can live in an ecosystem.
<CROPPING
SYSTEMS FOR SINGLE ANNUAL RAINFALL>
03p21.gif (600x600)
In rainfed areas, the distribution and
amount of rainfall are
perhaps the
most critical determinants of the types of cropping
systems that
can be adopted. In some areas where
rainfall is limited,
irrigation is
not feasible. Crops that require less
water are the
obvious
choice for such areas. Water-conserving
measures such as
mulching,
fallowing, and terracing can often conserve enough water
to make the
difference between profit and loss. In
areas where
annual
rainfall is over 600 mm, cropping systems are generally based
on
maize. In areas where rainfall is over
1,500 mm per year, cropping
systems are
often based on rice. Other crops grown
with the
latter
rainfall pattern are roots, cocoyams, tubers, plantains, and
bananas among
others. For example in Southeast Asia,
various crop
systems fit
the rainfall pattern, which is a single annual rainy
season.
Since rice needs more water than other
cereal crops, and
because it is
the only major crop that tolerates flooding, only rice is
grown at the
peak of the rains. Upland crops can be
planted at the
beginning
and/or end of the rains to utilize residual moisture and
higher light
intensities during the dry season (System I).
Mixed
cropping
systems, such as, maize and groundnuts, are often best
reserved
until the end of the rainy season (System II).
Natural sites are able to support a number
of plants and
animals.
The limits of this support are determined by
the availability
of the
elements needed for life. This limit is
known as the site's
biological
potential or carrying capacity.
Obviously, the biological
potential of
a fertile flood plain is much greater than that of arid
lands of the
same size because more water, better soil, and more
nutrients are
available to organisms living there.
Biological potential can be increased by
adjusting the limiting
factors.
Crop production can be increased by adding
limiting elements.
These might
be fertilizer, organic matter, water, or some
form of pest
control. Improved technology can also
affect limiting
factors.
When considering limiting factors,
remember:
* Satisfying the most obvious limiting
factor may not solve the
problem.
In fact, satisfying one limiting factor may reveal
yet another.
For example, when nitrogen is lacking in a
corn field, the farmer may add a
nitrogenous fertilizer. He
may then find that nitrogen-induced crop
growth attracts a
greater pest attack, thus revealing a
new limiting factor.
* There are upper and lower limits to the
amounts of nutrients
plants can use.
* Changing present conditions by adding
limiting factors may
harm currently adapted organisms.
Understanding the concept of limiting
factors and knowledge of
how
ecosystems function constitute a basis for drawing up appropriate
and
ecologically sound guidelines for planning agricultural projects
that are more
sustainable.
HOW KNOWLEDGE OF ENVIRONMENTAL CONCEPTS
AND
IMPACTS CAN BE USED TO ENSURE
MORE SUCCESSFUL PROJECTS
A feasibility study of a project should
consider potential ecological
change, as
well as economic, social, and cultural factors that may
influence the
project. If this process indicates a
number of possible
good and/or
bad effects, the development worker then looks for
acceptable
alternatives or makes what seem to be acceptable
trade-offs or
compromises based on the situation. For
example, if
people are
starving and increased crop production seems to require
use of a
pesticide that may be harmful, the decision will depend on
the urgency
of the situation, but the planners and the community
need to be
aware of the implications of pesticide use and take
precautions.
In order for small-scale agricultural
efforts to benefit from an
environmentally
sound approach, planners should be aware of the
environmental
factors impinging on the type of agricultural project
being
considered, and then utilize this information to design management
options that
limit environmental impacts.
PART II:
PLANNING FOR SUSTAINABLE
AGRICULTURE
CHAPTER 3
THE PLANNING PROCESS
This book contends that all development
activities must have a
substantial
basis of local participation in planning, decision making,
and
implementation. Planning is often
described as a linear process
of
identifying needs, proceeding to project objectives, and designing a
project to
meet those objectives. In reality the
process is and should
be more
complex. Effective planning of a
project is a dynamic
process
involving the beneficiaries, the implementors, and any outsiders
who are
assisting. The initiator may be the
community itself
or it may be
an outside development assistance agent or organization.
In either
case the partnership relations between the community
and outside
assistance must be balanced if the development
activity is
to belong to the community.
WHO PLANS
Planning can be done on an international,
national, regional, or
local
level. It may be initiated by the local
community people on
their own
initiative, by nongovernmental organizations, by regional
government
officers, or personnel of national universities or ministries.
Whatever the
level or whoever the initiators, the sustainability
of the
activities will be depend on the involvement in the planning
and decision
making of those the project is intended to benefit.
THE END IS THE BEGINNING
Meeting the needs of beneficiaries is both
the beginning and
the end goal
of development activities. If the
initiator is a community
group, group
members need to sit together and explore their
needs and the
resources available to meet those needs.
If the
initiators
are external to the community, they need to sit with the
community and
identify needs and resources from the local perspective.
A local group organizing a project must
establish a clear
picture of
itself and the natural resource base.
External agencies
must also
gather a profile of the community and a profile of the
resource
bases of the activity.
The next step is for the community to
define the goals and
objectives of
the activity being undertaken to meet identified needs.
If there is
an external agency involved the process should be collaborative.
Plans for the
activity can be made based on the ultimate
goal and the
specific objectives. This part of the
planning process
needs to be
done with conscious recognition of the tradeoffs involved
in meeting
needs with limited resources and the realities of politics,
cultural
values, and preservation of the natural resource base.
The project may need input of a technical
nature in design,
implementation,
monitoring, and redesigning. If there
is external
assistance,
the evaluation should not be external but participatory.
Various quantitative techniques may be
used to help complete
the basic
phases of the planning process. Such
techniques will help
establish a
baseline against which to measure accomplishments.
Some of these
quantitative techniques can be quite detailed, requiring
the use of
computer programs and simulation techniques.
Customarily,
a development
worker will not have ready access to computer
programs and
simulation techniques. In that case, it
is helpful
to have a
checklist for a guide as planning proceeds.
Some checklists
that may be
useful can be found later in this chapter.
A
framework
outlining this planning process is on the following page.
FLEXIBLE PLANNING
Flexible planning is the ability to use a
framework and the
information
and perspective provided by it creatively in designing a
project.
<PLANNING:
A DIALOGUE>
03p26.gif (600x600)
A planning framework/methodology presents
a logical, step-by--step
method for
defining and integrating project variables and for
choosing
among project opportunities. Because
the steps in the
planning
process have been lifted out of a "real context," they may
appear neat and
well ordered. In reality, the steps to
be taken in a
given project
are not likely to be clear-cut (at least initially) and the
variables and
components may be difficult to categorize.
A good
methodology
helps the user work through the mass of information
available to
structure steps that are possible and feasible.
For
example, a
planner can use this methodology to determine priority
among a
number of possible projects and to decide when a project
design,
perhaps because of a likely imbalance in benefits/costs terms,
should be
changed.
The key to good planning is applying a
problem-solving approach
flexibly
within pre-determined boundaries. The
boundaries,
or
guidelines, are things that should not be changed--except for very
good
reasons. Certain aspects of a project
can be altered easily
because they
represent different methods of accomplishing the project
within the
same boundaries. Alterations that do
change the boundaries
must be made
only with great caution. These
guidelines, once
set, can provide
the basis for an environmentally sound, small-scale
agricultural
project in various local situations and with alternative
project
designs.
1. IDENTIFY AND ASSESS NEEDS AND
CONSTRAINTS
When community members participate in all
phases of project
planning,
execution, and evaluation, they will be more committed to
the project
and have a sense of ownership. Arousing
and maintaining
community
participation is a challenging task. It
is not
difficult to
communicate with one or two leaders or a small group.
However,
involving the whole community and helping them to realize
what can be
achieved is more difficult. Some
references on the
subject are
included in Appendix A.
Planners and community members may not
always agree on
the priority
needs of a community. Each is looking
at the problem
from their
own point of view. If planners begin a
project that addresses
needs that
are not identified by the community, there will be
insufficient
support from the community. With the
participation of
local people,
planners can learn which issues are critical to the
community.
Communities are groups of individuals that
may have conflicting
goals.
If the project satisfies only the goals of
certain members
of the
community, planners should make sure that the project does
no harm to
those who are not participating. A
project that satisfies
the needs of
several different groups within the community will be
more
sustainable.
Where commercial sales of agricultural
products are involved,
wholesalers,
retailers, and transporters should be included in planning.
These groups
are experienced with marketing problems and
with past
successes and failures. If all related
groups are included
in the
development process, they can explore the reasons why projects
have failed,
so that mistakes are not repeated.
2. COMMUNITY PROFILE AND NATURAL
RESOURCE PROFILE
Community
Profile
A community profile can be an important
tool for the development
worker from
outside the community as well as a community
group
planning a project. The profile should
be structured so that it
will provide
easy-to-use data on key social, economic, cultural, and
natural
characteristics of the community or region.
The profile does
not have to
be prepared in great detail, nor should it take weeks and
months to
complete. The topics suggested here for
inclusion highlight
agricultural
activities. The user will want to gear
the profile so
it yields
data relevant to the primary area of concern.
* Determine the social structure and
kinship relationships of
the community.
Note these particularly as they pertain to
agricultural activities such as
cultivating, harvesting, marketing,
etc.
* Understand the traditional roles of men
and women in relation
to the agricultural system.
Include all related activities
such as land preparation, planning,
harvesting, storage, sale
and other aspects of crop management.
* Note the cultural traditions and
folkways of the community
associated with food production.
* Identify community leaders, their
spheres of influence, and
how these may or may not affect
agricultural activities.
* Analyze the economy of the community and
the area, especially
as it relates to phases of agricultural production, such
as cultivation, harvest and post-harvest
activities.
* Consider marketing opportunities or lack
of markets.
* Note land use and ownership patterns.
* Note availability of such services, as
credit mechanisms,
agricultural extension, and agricultural
information.
* Determine people's ability to put more
time into crop production
or to take risks.
* Include a range of perspectives among
community members
on agricultural and personal needs and
the priority of each
need.
* Verify all of the above with the
community.
The planner will also want to be sure that
the community
profile
encompasses all the information that is relevant to the community
and the
project.
Natural
Resource Profile or Inventory
A survey of the natural environment
(climate, soil, topography,
rainfall,
soil fertility, pests, etc.) provides information necessary for
assessing
project feasibility and for determining potential benefits
and costs as
well as required modification. For
small-scale projects,
the inventory
need not be turned into an intensive study, but rather
a rapid rural
appraisal method. It can be a useful
tool providing a
baseline to
which to refer after the project is underway.
There are at least two levels at which
inventories should be
done.
The first consists of creating an overview
picture of the area
ecosystem.
As part of this inventory, the planner
should look at
such things
as watershed characteristics, significant topographical
features,
general rainfall distribution patterns, general climatic
information.
This information may be available through
local
sources, by
observation, or discussion with local people.
The second inventory is a localized
biophysical and socio-economic
review.
The biophysical evaluation entails an
identification of
land types,
cropping systems, farming systems determinants, and the
interactions
among farm components. The
socio-economic review
analyzes the
resources needed for the farming systems (human
resources,
land, credit, capital, etc.) on a seasonal basis.
Learning from
Local Agricultural Experience. Learning
from local
agricultural
experience is important because agricultural practices in
many
countries are already well-adapted to prevailing environmental
conditions.
Over many years of trial and error, farmers
have developed
systems that
work. As more research is conducted,
many
farming
practices, once regarded as primitive or misguided are now
recognized as
sophisticated and appropriate.
Confronted with specific
problems of
slope, flooding, droughts, pests and diseases, and low soil
fertility,
small farmers throughout the world have developed unique
management
systems aimed at overcoming these constraints.
By learning about local practices, it is
possible to obtain further
information
on (Chambers 3.5):
- local crop varieties that have shown
particular resistance to
disease and pests
- cropping methods, such as intercropping
and multiple cropping,
that are designed to get the most out of
small land
areas
- availability and use of organic
fertilizers (e.g., manure and
compost) that do not have to be
purchased
- agricultural methods that conserve
water, soil, and nutrients
- agricultural methods that may require
less time, money, and
labor than some other alternatives
- agricultural tools which are made
locally and are suited to
local needs
All this information can serve as a
starting point to develop
appropriate
agricultural systems and technologies adapted to local
conditions.
This inventory should also cover the
following among other
things:
Agricultural
Practices
* What crops are grown and why?
* Who is growing which crops (men or
women)?
* Are crops grown for consumption, cash,
medicine or other?
* What local resources are available for
food production? Are
they used efficiently?
* Are there food shortages or surpluses?
* What are the major causes of crop loss?
* Are pests a serious problem?
Which ones?
Which pest
control methods are in use?
* Do current crops provide adequate
nutrition for human diet?
* Do current cropping systems improve or
lessen the nutrient
content of the soil?
* Do local agricultural practices promote
or otherwise enhance
watershed management and soil
conservation?
Soil
* What types of soils dominate?
* What is the organic and nutrient content
of the soil?
* Are there signs of degradation, such as
compaction, erosion,
light colored soils?
* Is wind erosion a problem?
* What is the topography and how does it
affect soil quality
and water/soil relations?
* What kinds of organisms does the soil
contain? Are earthworms,
protozoa, grubs present?
* What fertilizing practices are used, if
any? What ingredients
are available for composting?
Water
* What are the major local sources of
water? Is the same
water source used by both animals and
people?
* Is the water of good quality?
* What water-carrying methods are used to
bring water to
crops?
* Is the water table relatively stable?
* What kind of vegetation exists around
the water source?
* Is the supply of water steady year
round?
* Is there much fluctuation in water
supply due to heavy
flooding or drought?
* What type of watershed management is
used?
Climate
* What are the rainfall/sunshine patterns?
* Do floods and droughts present serious
seasonal problems?
* Is altitude an important factor?
* Is wind a predominant feature?
Land Tenure
* Who owns the land in the community?
* How many are landless and engage in
day-labor on other's
land?
* What are the characteristics of the land
available for farming,
for example size, existence of or
potential for irrigation,
topography, land cover?
* Is the land titled or registered?
* Can additional land be acquired?
* Who owns or controls water sources and
water rights?
* Is land being priced out of the
agricultural market?
The above checklists of questions should
help to meet the
ultimate
objectives of the survey which are to:
* Define the productive potential of each
agroecological zone.
* Delineate the limiting factors (i.e.,
zones of moisture surplus
or deficit) so that appropriate
techniques of resource conservation
are developed.
* Identify other areas with similar
ecological environments and
social contexts, so that technology
developed in one environment
can be transferred.
* Facilitate the choice of appropriate
agricultural inputs and
technologies and quantify the levels of
risks associated with
them.
* Promote development of sustainable
farming systems with
well defined inputs, calendars, and
outputs.
3.
DEFINE GOALS AND OBJECTIVES
After the community has identified needs
with the highest
priority, the
goals and objectives that address these needs can be
formulated by
the group. A goal is an overall purpose
for undertaking
the
project. The objectives help direct
action toward this
general
purpose.
Objectives are the more specific targets
that will be achieved
by the
project. Objectives should be clearly
defined, measurable, and
feasible.
An objective should indicate what is to be
achieved, when
it will be
completed, and how success will be measured.
The objective
should state
actual numbers, such as, the number of hectares
involved, the
kind of crops to be produced, the number of wells to be
constructed,
and so forth.
If the objective states when achievements
are expected, it
provides the
time line for achieving the objective.
A valuable outcome
of
formulating objectives is that information needs become
clarified.
Once project objectives have been
established, the ways to
reach these
objectives can be considered. It may
assist in developing
objectives
for the community to answer the following questions.
* What is the overall purpose or long
range goal? (example:
increase income, improve nutrition)
* Who will be responsible for achieving
that goal?
* How do the relations between and
responsibilities of both
men and women affect that achievement?
* Who will benefit from the project?
Are they the same people
who are responsible for achieving the
benefits?
* How can progress toward achievement of
the goal be measured?
* What results would indicate that the
goal was reached?
* In what time frame can these results be
expected?
* Over what geographical area will the
project extend?
Answers to these questions can be combined
into several
coherent
objectives.
4. DESIGN
PROJECT WITH CONSIDERATION
OF TRADE-OFFS
Once objectives are defined, members of
the community in
consultation
with development workers and technical personnel can
design means
to achieve the objectives. Informed and
constructive
opinions can
be helpful in reaching decisions. Some
of the key
elements in
designing agricultural activities are listed in the box on
this page.
KEY ELEMENTS FOR DESIGNING
AGRICULTURAL ACTIVITIES
- start small
- include local participation at every stage
- start with knowledge and information from
the community
enhanced with technical information
- seek technical information on soil, water,
crops and seeds
- include training in the basic plan
- consider integration of conflicting land
uses (agriculture, forestry,
livestock) to maximize productivity of the
farm system
- consider alternatives to chemical
pesticides and fertilizers
- where tree planting is involved plan for
maintenance and
harvesting of the trees
- benefit the whole community
- build evaluation into the dynamic of
implementing the planned
activities/project
Source:
Weber 3.8
In preparing alternative courses of action
predictions should be
made of
probable impacts, both negative and positive, of the proposed
activity.
Choices often involve trade-offs.
A choice that has strong
positive
benefits may also have negative effects.
For this reason, the
costs and
benefits of each alternative are often compared with each
other, using
a standardized format. This is called a
cost-benefit
analysis.
References that can provide methodology for
analyzing
trade-offs
and cost benefit analysis can be found in Appendix A.
5.
IMPLEMENT THE ACTIVITY
After alternative designs have been
examined, the sequential
steps needed
to put the plan into action can be finalized and a
tentative
timeline established. Meeting the
objectives of the project
depends upon
continuous community participation, development of
local
leadership, and consideration of community dynamics.
A plan
that is
adapted to the local environment should utilize local materials
and local
expertise. It also should include
training in new
management
methods and other skills needed for project realization,
while taking
advantage of local knowledge of the environment.
Case studies have shown that farmers and
their families have
a good
understanding of their immediate environment.
Farmers
throughout
the world have developed traditional calendars to time
agricultural
activities. Thus many farmers sow
according to the
phase of the
moon, believing that there are lunar phases of rainfall.
Other farmers
cope with climatic seasonality by utilizing weather
indicators
based on the vegetative stages of local vegetation.
Training
Programs
Training is almost always needed when
innovation is being
introduced.
It is essential when larger or more complex
systems are
planned, when
new crops or trees are to be introduced, or when new
methods are
to be adopted. It may be necessary to
identify some
farmers who
are willing to risk being innovative.
These producers
are more
likely to achieve increased yields and are often easily
identifiable.
If such people are given special training,
and encouraged
by follow-up
support, they can often help in the training of other
members of
the community and can demonstrate project benefits.
Funding
Funding of projects is not always
necessary but sometimes it is
critical.
Small farmers usually have few resources and
little money
or time to
risk in a new enterprise. They may be
reluctant to enter
a loan
agreement in an untried venture.
However, the more sustainable
projects are
those in which the beneficiaries have made
some
sacrifice of time or have contributed resources.
Financial
assistance
sometimes may be needed from the local community,
government,
or other organizations in the form of loans and/or
grants.
6.
MONITOR THE PROJECT
Plans for monitoring the project should be
part of the original
design.
Systematic monitoring often detects
unexpected positive or
negative
impacts and modifications of project design can be made.
Because environmental and human interactions
are complex,
all project
effects cannot be predicted and changes may not be immediately
apparent.
Therefore, it is important to continue to
monitor
the project
in operation to observe both expected and unexpected
results.
Planners may want to monitor effects on
vegetation, water
quality, soil
fertility, land use, diet and cultural practices.
Such data
also will
help to identify maintenance procedures that will ensure
project
continuation.
7.
EVALUATE THE PROJECT
The project plan should outline the
evaluation methods to be
used, and
ensure that the evaluation is carried out.
Too often this
process is
ignored, especially when the project may not appear to be
achieving its
objectives. However, project evaluation
is important for
all who were
involved in a project. Every project
involves a certain
amount of
risk for project participants. In the
event of project
failure,
these participants must not be abandoned by planners or
they will
hesitate to try any future projects.
Evaluation must be a joint effort of
planners and community
members.
Outside evaluators may add fresh insight or
see solutions
to problems
overlooked by those close to the project.
However, they
also may
judge the project from their own value system that may not
fit project
purposes. The point is to observe and
measure how well
objectives
have been achieved and to determine if there have been
other
expected or unexpected results.
Investigation of the causes of
success and
failure will help future planners to improve project
designs.
Evaluations are especially helpful if the
project methods have
been
experimental, with no past history of success or failure in a
similar
environment. Planners and project
managers should exchange
information
with those in nearby regions in order to compare
methods and
results.
A SUMMARY CHECKLIST
* Are project objectives measurable and
realistic?
* Are they compatible with community
needs?
* Were community members involved in
establishment of project
objectives?
* Was a cost-benefit analysis which
includes an environmental
analysis used to help select the best
project design to achieve
objectives?
* Is an effective technical assistance and
training program
integrated into the project design?
* What assistance can be provided by
financial, governmental,
and other institutions or groups?
* Is there a reasonable plan to monitor
and evaluate the
project?
This chapter has outlined a planning
process. Chapter 4 contains
some
suggestions about the broad framework of understanding
needed for
planning. The chapters following
explore some of the
technical
issues that might be encountered in planning an agricultural
project.
Chapter 10 concludes with a checklist for
sustainable
projects,
examples of traditional systems, and a look at long term
evaluation.
CHAPTER 4
OTHER CONSIDERATIONS FOR
PLANNING
03p38.gif (437x437)
INTRODUCTION
Chapter 3 reviewed the process of
planning. The suggestions
in that
chapter, however, are not a prescription.
They need to be
adapted to
the local situation. In addition, there
are some other
considerations
that affect planning a project. There
are some natural
limitations,
involving biological and physical relationships.
These
will be
discussed in the chapters providing technical background for
planning.
This chapter will discuss legal constraints
to agricultural
activities; socio-cultural
considerations; and related to these, the
special
considerations of women's activities in agriculture.
<OTHER
CONSIDERATIONS FOR PLANNING>
Legal limitations, unlike natural
limitations, are established by
people to
meet specific conditions and, therefore, can be modified by
people in
response to changes in legal, social, and economic situations.
Socio-cultural
conditions have been established over time by
practical
use. Considerations concerning women in
agriculture are
not new but their
importance is newly recognized.
LEGAL CONSIDERATIONS
Among the important institutional
considerations in planning
small-scale
agricultural projects are the laws that affect the use of
land and
other resources.
Often in the rural areas of developing
countries the legal
status of
land ownership is ambiguous. Vast areas
of farm land
used by
low-income farmers is unregistered, with usage passing from
generation to
generation without legal protection.
These lands are
usually
marginal, lacking fertility and irrigation, and otherwise
undesirable
for agricultural production. Where
statutes are clear
with respect
to land ownership and distribution, for example, in a
land reform
program, enforcement is always mixed.
There may be a
correlation
between the level of poverty of the low-income farmer and
the issue of
security of land titles. Political
considerations color the
execution
process producing uneven results. Also
land prices can
make it
difficult for governments to acquire land for distribution.
As regards laws that address ownership,
use, and the sale of
the products
of natural resources, the development worker may be
faced with
dual legal systems in some jurisdictions:
a common law
system
inherited from the colonial period and customary law deriving
from
indigenous concepts of ownership and usage.
In parts of Africa,
for example,
land ownership may reside in the person of the tribal
chief.
Accordingly the use of the land and
distribution of products
will be subject
to his regulation. At the national
level a price
structure
established by the government to hold down the cost of
food in the
urban areas may make a small-scale commercial agricultural
project
unprofitable. Law always affects
development projects
at some
level, too often with negative results.
A development worker should consult with
local authorities to
be sure that
a small-scale agricultural project can be implemented
within the
existing land tenure jurisdiction and patterns of land
ownership.
SOCIO-CULTURAL CONSIDERATIONS
Legal considerations, as discussed above,
are formal rules that
guide social
conduct. Less explicit, but equally
important, are
guidelines
derived from other cultural practices of a society--from
tradition,
religion, and folklore. As with laws,
these social considerations
must be
reflected in the decision-making process.
Failure to do
so can lead
to adverse reactions that can severely affect the project.
Cultural considerations determine, in
part, the options available
to a planner
of environmentally sound small-scale agricultural
projects.
From the flood plains of the Mekong River
Basin to the
fragile
desert environments of northwestern Africa, situations can be
found in
which social patterns affect implementation of particular
agricultural
practices.
Social constraints are often difficult to
assess. They are not
usually
susceptible to easy solution and are often ignored.
However,
to do so is
folly. To increase the possibility of
environmentally sound
resource
management in agriculture, it is essential to include local
people in
planning objectives of the project.
Training and public
education are
also important.
Other socio-cultural factors such as
household relationships,
division of
labor between men and women, and decision making in
relation to
agricultural activities are sometimes critical to project
planning and
should not be overlooked. Some projects
increase the
burden on
women by increasing their responsibilities and working
time
involved, when the objective of the project is to reduce the
burden.
WOMEN AND AGRICULTURE
In many areas of the developing world,
women constitute
one-half or
more of the agricultural labor force and may be responsible
for producing
as much as 90 per cent of the food. It
is essential
to recognize
this in those regions where women traditionally are
the farmers,
producing food crops, managing small livestock, and
sometimes
cultivating cash crops. Women need to
have a role in
decision-making
about agricultural innovations and development
interventions.
They need to have access to training,
extension
programs that
are sympathetic to their traditional role, and they
need credit.
In the past, when new options existed,
they have been more
often
available to men rather than women. For
a large majority of
women,
especially in rural areas, innovation, training, and development
interventions
have not improved their quality of life.
In
many cases
just the opposite effect has been the result.
DIVISION OF RURAL LABOR BY
TASKS,
BY SEX:
ALL AFRICA
Percentage
of
Total
Labor in Hours
Men Women
Cuts down the
forest; stakes out fields 95
5
Turns the
soil
70 30
Plants the
seeds and cuttings 50
50
Hoes and weeds
30
70
Harvests
40
60
Transport
crops home from the field
20 80
Stores the
crops 20
80
Processes the
food crops 10
90
Markets the
excess 40
60
Carries the
water and the fuel 10
90
Cares for the
domestic animals 50
50
Hunts
90
10
Feeds and
cares for the family
5
95
Source:
UN Economic Commission for Africa, 1975, Women in
Africa.
If there is to be a shift to a better
understanding, the following
are some of
the constraints that need to be addressed:
* Most of the power is in the hands of
men; therefore men
have access to new opportunities.
* Women tend to be viewed as consumers
rather than as producers.
* Women's chores such as food processing,
fetching water and
fuelwood, child care, and cooking are
generally not considered
to be productive contributions to the
economy.
* When these chores offer income-producing
potential, they are
usually undertaken by men.
The preceding table demonstrates the
division of labor between
men and women
in Africa, where women traditionally play a dominant
role in
agriculture.
ECONOMIC CONSIDERATIONS
The local people and the development
worker must select from
alternative
plans of action. Choosing among
alternatives requires
some economic
considerations. Economics involves
patterns of
analysis,
sometimes referred to as benefit/cost analysis.
To make an economic analysis of
alternative courses of action,
three general
objectives form a basis of choice. The
objectives are to:
- provide the greatest possible benefits
for the costs incurred
- bring the best possible rate of return
on investment
- achieve a specified "production
goal" at the least cost
Analysis of these objectives can give the
local people and the
development
worker a better understanding of the economic implications
of selecting
a particular course of action.
To analyze the first two objectives,
likely consequences of
alternative
courses of action and costs of implementation must be
determined to
the extent possible. Some information
can be obtained
from previous
local experience. If the course of
action is newly
adopted, the
development worker can seek available prediction
techniques.
To satisfy the third objective, goals
should be established for
various
levels of production. These goals are
most effective if set
according to
values of local residents, coupled with long-range goals
derived
through the political process.
Benefits/costs analysis has often been
viewed as a purely
financial
approach rather than as a tool to use in a more
human-centered
development process. This view can be
dangerous
for at least
two reasons: 1) it can cause the
planner to overlook the
importance of
economic effects; 2) it can lead to a failure to recognize
that
cultural, social, and ecological factors also can (and should) be
considered in
benefits and costs terms. Planners must
be able to
bring a
benefits/costs approach to all facets of the planning process if
they are to
be able to judge project feasibility in terms of impact on
the
community.
PART III:
BACKGROUND FOR PLANNING
CHAPTER 5
SOIL MANAGEMENT
THROUGH REDUCTION OF
EROSION
03p44.gif (437x437)
Soil contains the nutrients and water that
plants need for
growth and
serves as the medium or substrate in which they grow.
The primary
purpose of soil management is to provide a continuously
supportive
and productive soil for plant growth through proper
provision of
water and nutrients and soil conservation practices.
When the soil is left without vegetative
cover, erosion may
result.
Since erosion is the most serious
environmental problem
facing many
farmers around the world, this chapter provides background
for planning
agricultural projects in areas that are prone or
subject to
erosion, and need controls to reduce erosion.
Before
beginning a
project, it is necessary to understand the process of
erosion and
its effects both upon the project and the environment.
<SOIL
MANAGEMENT THROUGH REDUCTION OF EROSION>
EROSION:
WHAT IS IT?
Erosion is movement of soil by water,
wind, ice, or other
geological
processes. It is a function of climate,
topography (slope),
soils,
vegetation, and human actions, such as cropping methods,
irrigation
practices, and equipment use. Usually
erosion control
becomes more
necessary as the slope of the land increases because
the slope
helps the soil to move.
There are three stages of water-caused
erosion: sheet erosion,
rill erosion,
and gully erosion.
Sheet Erosion
Intense rainfall or large rain drops
displace particles of soil.
Topsoil is
dislodged by this impact. As water
accumulates, it begins
to remove
soil more or less uniformly over a bare sloping surface.
Moving down
the slope, the water follows the path of least resistance,
such as
channels formed by tillage marks, stock trails, or
depressions
in the land surface. Sheet erosion is
the first stage of
damage and as
such can be hard to identify. Those
seeking to
develop a
piece of land should check carefully for signs.
One simple
method for
assessing erosion problems is to observe from the low end
of the field
what is happening during a heavy rainstorm; i.e., is the
run-off water
dark with accumulated soil?
Rill Erosion
Concentrated runoff may remove enough soil
to form small
channels,
tiny gullies, or rills in a field.
While rills are often the
first visible
sign of erosion, they can be covered up by tillage practices.
Learn to
recognize the signs of rill erosion and watch for
them.
Under continued rainfall, rill erosion
increases rapidly.
Steeper or
longer slopes increase the depth of the rill.
The erosion
potential of
flowing water increases as depth, velocity and turbulence
increase.
Sheet and rill erosion together account for
most of the soil
movement on
agricultural lands.
Gully Erosion
As water accumulates in narrow channels,
it continues to move
soil.
This is the most severe case of erosion and
can remove soil to
depths of 1
to 2 feet, or up to several hundred feet in extreme cases.
Laterite
Formation
There is a widespread belief that tropical
soils, once cleared,
are
irreversibly transformed into hardened plinthite or laterite.
Actually,
only a small proportion of tropical soils (for example, only 4
per cent of
the land in the Amazon) is subject to laterite formation.
Where there
is soft plinthite in the subsoil, and when the topsoil has
been removed
by erosion, hardening to laterite can take place.
Therefore
laterization is more likely to occur in soils where erosion is
extensive.
SOIL LOSS
The main factors that affect erodability
of a soil are the physical
structure and
chemical composition of the soil, the slope of the
land and the
management (how is it used) of the land.
(FAO 5.3)
Soil loss is
directly related to the following:
- intensity and amount of rainfall
- quality of the soil and how much it is
subject to erosion
- length of slope
- degree of gradient (steepness) of the
slope
- quantity of vegetation cover
- kind of crop system (monoculture or crop
associations and/or
sequences)
- system of soil management (especially
related to soil cover)
- erosion control practices (discussed later
in this chapter)
These factors
determine how much water enters the soil, how much
runs off, and
the potential impact for erosion. It is
essential to
evaluate
present and potential erosion in planning a project.
EROSION BY WIND ACTION
In arid and semi-arid regions, wind
erosion can be extremely
serious.
Topsoil blown away from the land can leave
the land
unproductive
and increase the number of particles in the atmosphere,
thus
affecting local climate. Wind erosion
can also:
- cover and kill plants
- disturb organisms living in the area
- increase labor and cost of cleaning
those areas which are
covered by soil
- reduce amount of solar energy (sunlight)
available to plants
- increase evaporation, surface drying
Extreme wind erosion, coupled with
climatic changes and
human
activities, can contribute to the formation of deserts.
For
example,
people contribute to increased wind erosion and hasten
desertification
by cutting woody species for firewood, overcultivation,
and other
practices such as improper cattle management that leads
to
overgrazing. In many cases, such
practices are the result of
increased
population pressures, but also because impoverished farmers
are pushed to
adopt these practices by social, political, and
economic
factors.
SOIL COVER AND WHY IT IS
IMPORTANT
FOR CONTROL OF EROSION
A good soil cover is the most important
control of both wind
and water
erosion. A cover directly on the soil
or close to it is the
most
effective. Soil cover serves the
following functions:
- interrupts rainfall so that the velocity
is slowed down before
it hits soil particles thereby reducing
splash and dislodging
effects of rain
- decreases runoff velocity by physically
restraining water and
soil movement
- increases ability of the soil to store
water by providing
shade, humus, and plant mulch
- improves surface soil porosity by root
systems that help
break up the soil and facilitate water infiltration
The leaves and branches of a crop provide
a canopy or cover
over the soil
and protect the soil from heavy rainfall and wind.
For
example, corn
forms a canopy several feet above the ground.
However,
this crop
leaves soil bare before seed germination and during
early crop
establishment. Shorter crops, such as
some grasses or
legumes
(beans, vetch), and crops such as sweet potatoes and squash,
provide cover
closer to the ground surface and have an even better
potential to
reduce erosion. Soil loss from a grass
and legume
meadow is
substantially lower than in a cornfield.
<CANOPY OF
TREES AND CROPS>
03p48.gif (486x486)
Ideally, projects should be designed so
that some kind of
vegetative
cover remains in place at all times.
This may not be
possible in
all ecosystems. If an area is cleared,
plan to cover the
cleared area
with vegetation as soon as possible. If
this is not
possible at
least take time to check, and encourage weeds to grow
naturally in
the fallow field. This is helpful in
three ways:
* The cover reduces the possibility of
soil erosion.
* The weeds can be plowed under to provide
nutrients (green
manure) for later crops and improved
soil structure.
* The balance of the ecosystem may be
reestablished to
ensure that the disturbance will not
have lasting, negative
effects.
HOW EROSION CAN BE
CONTROLLED
Erosion can be controlled by reducing the
mechanical forces of
water or
wind, by increasing the soil's resistance to erosion, or by
doing
both. Water erosion can be controlled
by preventing splash
erosion by
providing crop cover or a layer of mulch (crop residue or
other organic
materials) through which the rainfall then trickles
(infiltrates)
into the soil.
Another means of preventing erosion by
water is to constrain
any run-off
that continues to exceed the rate of infiltration.
This can
be done with
physical barriers such as contour-bunds, tied-ridges,
terraces
reinforced by rocks, ridges, or living barriers composed of
natural or
planted grasses or shrubs. Strip
cropping with furrows in
between using
sprinkler irrigation or trickle irrigation can also help
control water
erosion. Mulches and cover crops
sometimes deter both
water and
wind erosion. Wind erosion can also be
reduced by
planting
trees and/or shrubs as a windbreak.
(See figure below) A
windbreak in
addition can provide other benefits (firewood, fodder,
food, wood
poles) if multiple-use trees are planted.
Stubble mulching
is also used
in some areas to control wind erosion.
<FIGURE
1>
03p49.gif (437x437)
There are several ways to control erosion
caused by water. The
implementation
of each of these control measures may be a project in
itself, or
the measures may be included in agricultural projects.
Some common
methods are:
- increasing vegetation cover
- using plant residues to protect soil
(mulching)
- using improved tillage techniques such
as conservation
tillage
- rotating crops and planting cover crops
- reducing erodability of soil, for
example, by adding organic
matter
- planting deep rooted trees for slope
stability
- using mechanical support carefully
- and other practices such as terracing,
using diversion channels,
contour plowing and planting, strip
cropping, contour
strip cropping, tie-ridging, and
reducing of field lengths
HOW PLANT RESIDUES COMBAT
EROSION
Plant residues are, for example, corn
stalks, wheat chaff,
weeds, and
similar remains left in the field after crops have been
harvested.
They can provide effective erosion control
by reducing the
raindrop
impact on the soil and reducing runoff.
The practice of leaving plant residues on
the field is called
mulching.
Mulching is particularly useful for
protecting young
plants from
high soil temperatures, retaining soil moisture, and
contributing
to soil fertility as the residues decompose.
Mulch can be left on the surface, or it
can worked into the
topsoil by
plowing, discing, or harrowing. When
this latter practice
is followed,
the amount of organic matter in the soil increases and
the soil
structure or composition and water infiltration improve as
well as does
the water-holding capacity of soil. On
the other hand,
working mulch
into the soil reduces the percentage of surface cover
and loosens
soil so that it is somewhat more susceptible to wind and
water
erosion. Some pests as well as
disease-causing fungus and
bacteria may
thrive in the mulch and can be difficult to control.
The decision to plow plant residues into
the soil or to leave
them on the
surface depends upon the erodability of the soil in the
area, the
kind of organic materials, the amount of runoff expected,
and the
tillage practices used. The cost and availability
of the labor
to do the
plowing are also factors. Greatest
protection from erosion
may be
provided by not plowing mulch into the soil.
Yet, even when
mulch is
worked into the soil, more soil can be saved than would be
possible if
mulch were not used at all.
Some crop residues may have negative
effects as a mulch.
Local farmers
can be a good source of information on this point.
<EFFECTS
OF MULCHING>
03p51.gif (600x600)
IMPROVED
TILLAGE METHODS FOR EROSION CONTROL
As farmers are well aware, conventional tillage
methods leave
a bare soil
surface and expose soils to erosion until the crop is
established.
Tillage methods can affect the runoff
velocity of water, the rate
of
infiltration of water into soil, and the degree of soil compaction.
Compaction,
which occurs naturally in soils with a high clay content,
and hampers
root and plant development, can be worsened by the
use of heavy
field machinery, thus further increasing the chances of
erosion.
Following are three tillage techniques
that can reduce erosion:
reduced
tillage, conservation tillage, and no-till.
Reduced
Tillage
Soil is tilled as little as possible to
produce crops under existing
soil and
climatic conditions. Fields may be
plowed or harrowed,
but with
chisel plow rather than with moldboard plow.
Conservation
Tillage
Plant residues are usually left on the
surface as a mulch to
control weeds
and to conserve soil and water. Plowing
and planting
are done in
one operation with crop residues mixed into the soil
surface
between rows.
No-Till
Crops are planted directly into the field
or plot left untilled
after the
last harvest. No-till is done by
planting in narrow rows
between
previous crop residues. The surface
mulch of weed and crop
residues is
vital to the sustained success of 'no-till' and reduced
tillage
systems. In the tropics, in addition to
protecting the surface
soil against
the impact of raindrops, the mulch helps develop and
maintain the
soil surface and ensure rapid infiltration of water.
In some regions no-till needs to be
supplemented by carefully
designed
chemical weed control programs and increases in the rate of
fertilizer
application. Such additions require
more capital and also
sophisticated
management and planning.
Studies indicate that erosion associated
with conventional
tillage can
be reduced 50-90 per cent by a switch to any of the above
conservation
tillage practices.
Most development workers who work with
farmers in rural
situations
and plan projects should become familiar with these
practices,
and new advances in this area. For
example, improved
tillage
practices have been hampered in many areas by lack of
low-cost,
efficient tools for planting through the plant residue.
However, new
implements have been designed and tested to overcome
this
limitation such as the stick, the punch planter and the
single row
rolling injection planter (RIP), developed by the International
Institute of
Tropical Agriculture in Ibadan, Nigeria.
CROP ROTATION AND EROSION
CONTROL
Crop rotation is one way to reduce soil
erosion. Since the use
of different
crops in rotation reduces the amount of time a field is
left without
an adequate vegetative cover, erosion is reduced.
In
rotation of
legume forage crops with non-forage crops, erosion can be
reduced 25-30
per cent over continuous cropping. The
forage crops
can also
supply nitrogen for the crops that follow.
In addition, if the
rotation is
planned wisely, certain crops can be chosen for their
ability to
assist the resistance of soil to erosion under succeeding
crops.
The greatest of these residual effects is
derived from grass
and legume
meadows. Because they are sod-farming
crops, they
provide cover
and help build up the soil even when they are later
plowed during
conventional tillage. There may also be
residual
effects in
rotations using non-sod-forming crops.
For example, corn
leaves soil
less erodible than soybeans, but more erodible than small
grains.
In addition to planting crops with different
harvest times,
crops can be
planted between rows of permanent plant barriers such
as
broomstraw, elephant grass, or tree crops such as Leucaena.
This
technique,
called "alley cropping," will be discussed in Chapter 9.
SOME SUPPORT PRACTICES FOR EROSION
CONTROL
Support practices for erosion control may
require moving the
soil,
sometimes using machinery. The most
common practices--contour
plowing and
planting, and terracing--are practiced on long and
steep
slopes. These practices reduce erosion
by slowing down the
velocity of
water and its soil transporting capacity.
In semi-arid
regions,
these practices or variations of them can be used for conserving
water.
Contouring
Crops are planted horizontally on the
contour of the slope,
rather than
up and down the slope. This practice
has the effect of
creating
ridges across the land which reduce the rate of runoff.
Because small
barriers are provided by the rows the water moves
less quickly,
erosion is reduced, and the soil is able to absorb more
water.
Average rates of erosion on contour-farmed
land are about 61
per cent less
than on similar cropland planted without contours.
However, contour planting needs to be
planned carefully. On a
very steep
slope or in areas of heavy rainfall and easily eroded soils,
water can
build up in each contour, spill over, and break across
contour
lines. The volume of water can build up
with each broken
row, and the
result can be more erosion, not less.
Contour Strip
Cropping
Contoured strips of crops are alternated to
reduce the effect of
row
breakage. For example, when sod and
crops are planted in
alternating
strips, the sod reduces water flow and serves as a filter
to catch much
of the soil washed from a strip crop row.
Strips
structured
close to land contours give good erosion control.
Terracing
Terracing is a very old practice,
especially in mountainous
areas.
Terraces are costly in terms of the labor
needed to build
them and
require constant maintenance. When used
with contour
farming
practices, terraces are more effective for erosion control than
strip
cropping alone. Terraces reduce
effective slope length and
retain much
of the soil moved between terraces.
They can trap up
to 85 per
cent of the sediment eroded from a field.
Terraces are also
used in
semi-arid regions for conserving both water and soil.
However,
in tropical
climates where topsoil is thin, poor soil is sometimes
brought to
the surface. Raised beds also help
control erosion.
THE EFFECTS
OF SOIL MANAGEMENT/EROSION CONTROL
It is important to understand the
relationship among soil,
water, and
methods for erosion prevention and control, in order to
develop
alternative land management techniques.
The following
questions are
provided as a starting point for considering projects in
which
susceptibility of the soil to erosion is a significant limiting
factor for
crop production:
* Would improved tillage practices provide
better erosion
control?
If so, would there be obstacles--money, customs--or
other constraints to changing practices?
* Is the site subject to wind or surface
water erosion or land-slipping?
For example, does the site have a steep
slope? Is
it a windy area without protective
windbreaks? Is there
evidence of past landslides?
* Are there periods during the year when
the soil of the
project site is unprotected by
vegetative cover and subject to
sheet, rill, or gully erosion?
* Will erosion cause silt to form in
downstream water bodies
such as streams, lakes, and reservoirs?
* Will use of mechanical equipment on the
project site damage
the soil structure and leave the soil
more susceptible to
erosion.
* What is the major factor limiting
agricultural production in
the area?
Is erosion a major constraint to increased agricultural
production?
* What are the social, cultural, physical
and economic costs of
erosion?
* Can the project be set up to include a
training course for
local project participants?
* How have farmers traditionally adapted
to erosion problems?
* What other soil management practices may
be appropriate?
SOME ALTERNATIVES
Other tillage methods can be undertaken to
protect soil from
erosion.
These include:
- improving soil fertility
- timing of field operations
- plow-plant systems
- grassed outlets and grass waterways
- ridge planting with tie-ridges
- construction of ponds for runoff
collection
- changes in land use
- long low bunds, e.g., in the Sahel
These practices are described in the
following table, which is
based on
material from the U.S. Department of Agriculture and the
U.S.
Environmental Protection Agency. The
left-hand column gives
the name of
the practice; the right-hand column describes the advantages
and
disadvantages of each as an erosion control method
and describes
the potential effects of such a practice.
SUMMARY OF EROSION CONTROL PRACTICES
Practices
Highlights of Practices
No-till
Most effective for grasses,
small grains, and with
crop residues; reduces
labor and time required for
agriculture; provides
year-round control. Not
effective when soil is
too hard to allow root development.
Conservation
tillage Includes a variety of no-plow
systems to retain
some crop residues on
surface; more adaptable
than no-till but less
effective.
Sod-based rotations
Good meadows lose almost no soil and reduce
erosion of the next
crop; total soil loss is greatly
reduced but is unequally
distributed over rotation
cycle; may aid in
disease and pest control.
Crop
rotation Much less effective
than above; can provide more
soil protection than a
one-crop system; aids in
disease and pest
control.
Improved
soil Reduces soil loss as well
as increasing production
fertility
of crops.
Plow-plant
systems Rough, cloddy surface
increases the infiltration
rate and reduces
erosion; seedlings may be poor
unless moisture is
sufficient; mulch effect is lost
by plowing.
Contouring(*)
Can reduce soil loss up to 50 per
cent on moderate
slopes, less on steep
slopes; less effective if
rows break; cannot use
large farming equipment
on steep slopes; must be
supported with terraces
on long slopes.
Graded
rows Similar to contouring but
less likely to have
breaks in rows.
Contour
strip Rowcrops and hay in
rotation in alternate 15 to
cropping
30 meter strips reduce soil loss
to about 50 percent
of that with the same
rotation that is only
contoured; area used
must be suitable for across-slope
farming.
Terraces
Reduce erosion and conserve
moisture; allow
more intensive cropping;
some terraces have high
initial costs and
maintenance costs; cannot use
large machines; support contouring and agronomic
practices by reducing
effective slope length
and runoff
concentration. In tropical climates
where the topsoil is
usually very shallow, terracing
often leads to bringing
to the surface, soil
which is very poor.
This can have worse effects
than erosion.
Bund
terracing A technique for
terracing by creating bunds along
contours, then planting
seedlings on the bunds to
create a terrace.
This technique is used to replace
labor-intensive
terracing in Kenya and is
called Fanya Juu (does
by itself).
Alley
cropping Rotations of crops are
grown in between hedgerows
of fast-growing
leguminous shrubs or non-leguminous
fallow shrubs planted
along the contour
with the hedgerows
pruned from time to
time to provide mulch
and organic residues.
Live mulch
system Where crops are grown in rows
on ground covered
by leguminous cover
crops that are killed by
an herbicide along the rows where the crops such
as maize are
planted. Can minimize erosion on
steep slopes; most
suitable where there is adequate
rainfall.
Grassed
outlets Facilitate drainage of
graded rows and terrace
channels with little
erosion; are costly to build
and maintain.
Ridge
planting Reduces erosion by
concentrating runoff in mulch-covered
rows; most effective
when rows are across
slope; earlier drying
and warming of root zones.
Contour
listing Minimizes row breakover;
can reduce yearly soil
loss by 50 per cent;
disadvantages same as contouring.
Change in
land May be the only solution in
some cases. Where
use
other control practices
fail, may be better to
change to permanent
grass or forest; lost acreage
can be supplanted by
intensive use of less erodible
land.
Leaving the land to fallow is a common
practice in some areas.
Other
practices May use contour furrows,
diversions, sub-surface
drainage, closer row
spacing, intercropping, and
so on.
(*) A simple
means of finding the contour is with the "A" frame technique.
This method
is described in a brochure by World Neighbors
(see list of
agencies in Appendix B). World
Neighbors also has slides
or filmstrip
about the technique.
CHAPTER 6
WATER SUPPLY AND
MANAGEMENT
An understanding of the relationship
between water and
agriculture
is key to planning environmentally sound projects.
With
this
knowledge a development worker can judge a proposed water
supply or
control practice in terms of its impact on the environment
in which the
agricultural project is taking place.
As the primary transport medium on
agricultural lands, water
can be both
friend and enemy. Water carries or
moves nutrients
through the
soil to plants and within the plants themselves.
Water
removes soil
particles by the process of erosion. It
also moves
agricultural
chemicals from the fields into the surrounding environment
where they
can cause serious problems. An
understanding of
how water
moves and what its effects are on agricultural lands is
the key to
knowing how, when, and where a given project may
interfere
with these processes.
<THE WATER
CYCLE>
03p59.gif (600x600)
THE MAJOR SOURCES OF WATER
Surface water
Lakes, ponds, streams, and rivers provide
water to plants
either
indirectly through evaporation and later condensation over
agricultural
lands as rain, or directly, by tapping and channeling for
irrigation
purposes.
Rain
Rainfall is the climatic factor that most
drastically affects
agriculture
in the tropics. Rain falls directly on
plants and moves
down, or
percolates, through the soil to the roots and on to groundwater
supplies.
The important characteristics of rainfall
that affect agricultural
growth are
the amount, intensity, variability, and lengths of dry
spells and of
rainy seasons. The amount of rain
varies greatly from
season to
season and from area to area. In many places,
records--if
kept--of the
amount of rainfall can be used to identify patterns in
the amounts
of water available and to identify both flooding and
drought
cycles. It is helpful to establish the
amount of rainfall and
the amount of
evaporation/transpiration (see glossary).
In a climate
with a
well-defined wet and dry season, the growing season will
begin when
rainfall exceeds evaporation/ transpiration and continue
until the
soil water reserve is exhausted.
Understanding the moisture
patterns and
any changes in the patterns is of crucial importance
for
developing cropping systems adapted to local rainfall
conditions.
Groundwater
Water accumulates in the soil at various
depths depending
upon soil and
geologic structures. These groundwater
supplies are
relatively
permanent. Groundwater can move up
through the soil by
capillary
action to become available to plants at times when there is
not enough
rain. Under drought conditions,
however, this source
may not
help. Water held in deep pockets, called
aquifers, can be
made
available by digging wells.
THE WATER BALANCE IN CROPLANDS
The water balance or amount available to
the farming system
over a
specific period of time reflects factors affecting sources of
water.
What water is left in the soil around the
root zone of the
crops can be
calculated by balancing the following:
- what is left of the water from the
rainfall after runoff (water
moving below the surface soil, for
example, on top of an
impermeable layer of clay, towards a
stream)
- percolation below the root zone (water
seeping down through
the soil to the water table or the
groundwater supply)
- evaporation (from the soil)
- transpiration (moisture given off by the
crop)
The balance between rainfall and
evapotranspiration initially
determines
the amount of water available for crop growth.
When
rainfall
exceeds evapotranspiration the root zone is charged with
water.
As evapotranspiration begins to exceed
rainfall, water available
for crop
growth decreases. Runoff and
percolation also will affect
the amount of
water remaining in the root zone.
The objective of water management in
agriculture is to minimize
and utilize
the runoff, percolation, and evapotranspiration.
Practices
such as mulching and no-tillage can reduce evapotranspiration,
whereas
terracing can reduce runoff.
HOW WATER MOVES AND THE EFFECTS
Regardless of the source, water moves
materials to and from
the project
site physically and chemically.
Physical
Transport
Raindrops falling on unprotected soil
dislodge soil particles and
carry them
over the surface of the land. This
surface water runoff
can be a
major cause of erosion. Erosion has
three negative effects:
- loss of valuable topsoil, making land
less productive where
runoff takes place (however, nutrient
laden sediment may
enrich soil in lowland areas)
- pollution of streams and lakes
downstream from the project
site by soil particles that accumulate
and become sediment
- washing of fine particles into spaces
between larger soil
particles creating a physical block
which reduces water
percolation
Sediment from this process chokes streams,
decreases the
amount of
light that can penetrate the water, and clogs the gills of
fish and
shellfish. Nutrients and pesticide
chemicals adhering to
eroded soil
particles increase their polluting effects in the water.
On the other hand, physical movement of
the soil can have
beneficial
effects. For example, in flood plains
many agricultural
lands receive
fertile top soil as a result of annual floods that transport
soil from
sites upstream.
Chemical
Transport
Many minerals, nutrients, and pesticides or
fertilizers and
other
chemicals are dissolved and carried in water (or leached) out of
the
soil. This occurs by surface and
sub-surface runoff, and also by
water seeping
down through the soil (percolation).
Sub-surface
runoff picks
up chemicals, nutrients, and sediment, and deposits
them in
surface waters. A number of negative
effects can result
from this
chemical transport. For example,
pesticides can kill
aquatic
organisms and fertilizers promote growth of algae that may
pollute the
water. The extent of the impact depends
upon the
amount of
runoff, the chemicals carried, and their concentration in
the surface
water. Through percolation, water may
carry soluble
agricultural
chemicals directly to wells or to surface streams as part
of the
groundwater. Percolation may move
nutrients beyond the root
zone of
plants. The amount and frequency of
deep percolation
depends upon
the water storage capacity of the soil, the vegetative
cover, the
amount of runoff and rainfall, and the type of soil and
geologic
conditions below the root zone.
Percolation has beneficial effects as
well. One of these is moving
dissolved
salts deeper into the soil. When this
does not occur,
salts can
accumulate in the topsoil and eventually become toxic to
agricultural
plants.
THE IMPORTANCE OF IRRIGATED AGRICULTURE
Water management seeks to ensure the best
use of available
water.
In many areas and in many small-scale
agricultural projects,
the major
problem, at least initially, is inadequate water supply.
A
common answer
is irrigated agriculture, although water conserving
cropping
systems and drought tolerant crops might also be appropriate.
Before a decision is made about irrigation
it is important to
know the
amount and timing of rainfall that can be expected during
the growing
season and how rapidly this water will be depleted.
Many times
even though rainfall appears to be adequate, its monthly
distribution
should be considered in relation to potential evapotranspiration.
For example,
although total annual rainfall as shown in
the figure
below, is adequate for crop growth, moisture is in excess
from
September to May but inadequate from May through August, so
irrigation is
recommended during the period of peak evapotranspiration.
Agricultural lands are irrigated in many
ways. The best
method to use
depends upon:
- supply of water available
- quality of water
- slope of the site
- infiltration and percolation rates of
the soil
- water-holding capacity of the soil
- chemical characteristics of the soil
(salinity, alkalinity, and
so forth)
- moisture requirements of the crop
- weather conditions of the area
- economic resources of the farmers,
especially for moving
water to the field
- techniques for moving water to the field
<SIGNIFICANT
PHASES OF THE WATER BALANCE IN A UNI-MODAL RAINFALL CLIMATE>
03p64.gif (600x600)
WHY IT IS NECESSARY TO PLAN
IRRIGATION PROJECTS CAREFULLY
Irrigation projects can have far-reaching
effects on the environment
of a vast
area. Irrigation can affect the
water-table depth,
water
quality, soil characteristics, crop productivity, human health
(the spread
of diseases such as malaria and schistosomiasis), family
structures
and mobility patterns, economic status of farmers, water
rights, and
land ownership patterns. The land
ownership issue is
very
important because once land is irrigated its value is increased
dramatically
and what was once marginal land, now becomes quite
productive
and desirable. If the land title is not
secure in the hands
of the
low-income farmers, they could lose the land to an unknown
registered
owner. These possibilities should be
carefully considered.
Irrigation projects also can be affected
by other factors. Control
of water
sources needs to be considered. For
example, the
watershed
that will be providing water for the project should be
checked to
determine if the watershed is protected adequately to
ensure water
of the quality and quantity needed for proposed crops.
Watershed
development upstream from the project site could alter
the water
supply drastically, causing flooding, drought, fluctuations
in seasonal
flow, or water contamination. Other
uses of water closer
to the source
can affect the supplies and possibly pollute the water.
USING SURFACE WATER FOR
IRRIGATION
Using surface water for irrigation can
have far-reaching effects.
Irrigation
water usually is diverted via canals, ditches, and channels
from surface
waters nearby.
<FIGURE
2>
03p65.gif (540x540)
Effect on the
Aquatic Environment
* Removal of water for irrigation can
result in reduced flow
downstream.
* Reduced flow can cause the death of
aquatic plants and
animals.
* Water returned to the stream after
irrigation is often of
poorer quality than the original water,
and may cause death
of plants and animals.
Effect On
Farmland
Water carried to irrigated fields is also
subject to evaporation
from open
canals or seepage from canals in areas where the soils are
permeable.
On the other hand, when irrigation from
surface waters
spreads out
over the land surface, the water percolates downward
and can
accumulate underground. Over a period
of time accumulated
subsurface
water can raise the water table until it is within a
meter or even
a few centimeters of the soil surface.
High water
tables can
inhibit the growth of plant roots by waterlogging the soil.
Irrigation
may also change the wet-dry cycle and increase pest
problems and
incidence of certain diseases. Many
insect populations
die back to
low levels during the dry season. With
irrigation, pests
may continue
to breed throughout the year.
Salinization
and Alkalinization
Improper irrigation can have various
negative impacts on the
soil that
will affect crops. Among these are
salinization and alkalinization.
Soils that
contain more or fewer salts are better for different
kinds of
crops. The measure for whether soil is
alkaline or acid is
called
pH. The normal pH balance in soils is
around 7. If the soil
is above
normal acidity the pH reading will be higher than 7.
If the
soil is below
normal or alkaline, the pH reading will be less than 7.
Salinization.
In soils with drainage problems and improper
irrigation
the soil
surface can become very salty as water evaporates from
it leaving
deposited salts in the upper layers of the soil (salinization).
Salinization
is the concentration of salts--sodium, calcium, magnesium,
and
potassium--in the upper soil layers or on the surface in the
form of a
white crust or powder. Salinization if
uncorrected can
drastically
reduce crop productivity. When drainage
is adequate,
salts usually
present no problems. Salts can be
washed out of the
soil by
applying water in excess of the rate of evapotranspiration of
plants.
Where drainage is poor, concentration of
mineral salts can
occur when
surplus water accumulates and raises the water table to
within one
meter or less of the surface so that increased evaporation
leads to
salinization.
Inadequate drainage and elevated water
tables are the underlying
cause of
salinization problems in irrigation projects.
Awareness
of the nature
of this problem and its causes is another planning tool.
Development
workers must check drainage and water table characteristics
before
developing an agricultural project using surface
waters for
irrigation. The saline problem can be
corrected through
drainage,
which could cause saline contamination of groundwater and
surface
waters elsewhere. An alternative to
transporting the saline
drainage
water elsewhere would be to use it on-site for irrigation of
salt-tolerant
crops such as barley, cotton, sugar beet, wild rye.
Sensitive
crops are beans, onions, and most fruit trees.
Salinization can also be caused by small
amounts of water if
the water is
of poor quality. It is a common problem
where water
supply is
limited and there is a need to save it.
Alkalinization.
Another possible consequence of improper
irrigation
is
alkalinization which is of particular concern in arid and semi-arid
regions.
Alkaline soils are those with a high content
of exchangeable
sodium
whether or not in combination with substantial quantities of
soluble
salts.
Alkalinization is more serious than
salinization because it is
harder to
remedy. Salinization can be remedied by
applying water;
leaching
alkaline soils may worsen their condition.
Sodium, unlike
other soluble
salts, does not leach away because it is adsorbed (clings
to the
surface of soil particles and combines with water in a chemical
reaction) to
clay and organic matter. While salts
may be leached
away by
runoff or irrigation water, the sodium remains in the form
of sodium
hydroxide or sodium carbonate. The
presence of the
sodium
hydroxide causes the organic matter in the soil to dissolve
and destroys
the soil structure, making it difficult to till and almost
impermeable
by water. Expert technical assistance
is needed to
correct this
soil condition.
Technical assistance is required to
determine whether or not
these
conditions exist and how serious they are.
One easy way to
get help is
to take a soil sample to a government office.
World
Neighbors has
a pamphlet describing "How to Take a Soil Sample."
See Appendix
B for the address.
USING GROUNDWATER FOR
IRRIGATION
When water for large-scale irrigation is
drawn from groundwater
supplies by
sinking wells and pumping, the water table is often
lowered.
This has several possible effects that must
be considered by
the project
planner:
* Local vegetation may no longer be able
to draw on the water
table.
* Marshes, springs, and wet places may dry
up.
* River and stream flow may be reduced.
* The land may sink, or subside, if too
much water has been
pumped out too quickly from natural
underground water
storage areas, or aquifers.
This phenomenon is irreversible
(that is, it cannot be restored to its
former state by natural
means).
* Heavy withdrawal of groundwater can also
lead to saltwater
contamination of the fresh water in the
aquifer.
* If too much water is applied,
waterlogging may occur in
certain areas.
IRRIGATION RETURN FLOWS AND THEIR EFFECTS
Water used for irrigation flows back to
water sources through
transport processes.
This return flow from irrigation can be a
significant
polluter of surface waters, groundwater, and soil.
Small-scale
projects
usually do not exert excessive withdrawal of water,
since normal
discharge of groundwater may occur through springs,
and through
seepage along the sides of streams.
However, reduced
surface water
availability forces areas with marginal water supplies
to pump
groundwater, which increases water mining and costs of the
project due
to high energy requirements. Dissolved
salts, for example,
can be
carried to the subsoil or groundwater.
Water percolating
through the
ground carries with it the salts accumulated in the
root zone and
moves them up or down in the soil profile.
Some salts
also wash
into drainage systems and are returned to main streams.
<FIGURE
3>
03p69.gif (486x486)
When irrigation water returns to main
streams it may have
adverse
effects:
* Because of leaching and evaporation in
the fields and canals,
the salt content of the irrigation
return flow may be much
greater than that of the initial water used.
Too much salt
can kill fish and other aquatic
organisms downstream from
the point of return.
* Return flows can carry pesticides, which
can be lethal to
beneficial aquatic organisms that
provide food for higher
organisms in the food web, including
humans.
* Irrigation flows can carry sediment or
silt, which raises the
beds of irrigation canals, changes the
direction of canals
(causing them to meander), clogs drains,
and fills the
streambeds of reservoirs and lakes
downstream.
<FIGURE
4>
03p70.gif (486x486)
IRRIGATION AND HUMAN HEALTH
The human health implications of
irrigation can be extremely
serious and
can include the following:
* Irrigation canals can carry chemical
pollution from one place
to another.
* Canals and ditches can provide new
places for the growth,
breeding, and reproduction of various
disease organisms, or
their vectors, and can be instrumental
in spreading these
diseases, especially if water is used
for drinking and/or
bathing.
* Slow-flowing or stagnant storage ponds,
supply canals, or
deeper drainage ditches are ideal
habitats for disease organisms.
This occurs particularly when canals
become choked
with aquatic weeds, which slow-the flow
of water and offer a
feeding ground for mosquitoes and other
aquatic organisms
that transmit disease.
Many of the most serious human
diseases (for example, malaria, yellow
fever, and schistosomiasis)
are carried by organisms such as snails
and mosquitoes.
* Although snails and mosquitoes that
spread disease can be
controlled by pesticides, these
pesticides may also kill the
eggs, larvae, and adults of many other
species of aquatic
animals.
Control of disease organisms with chemicals can
also harm fish-raising efforts in
irrigation canals and reservoirs.
Mosquitoes that transmit malaria can
develop resistance
to specific insecticides over time.
Pesticides also
accumulate in the food web and can cause
harm to humans
who use the water or eat fish grown in
contaminated water.
Note:
Alternatives to pesticides for mosquito control include
promoting
pathogens (i.e., Bacillus turringiensis var.
israelensis)
insect-eating
fish (Gambusia, the mosquito fish), birds and other
predators
(See Chapter 8 for information on biological pest control
methods).
DETERMINING THE EFFECTS OF WATER SUPPLY
AND MANAGEMENT PROJECTS
By formulating and answering a series of
questions like those
given below
for each project and site, development workers may be
able to
anticipate a few of the potential effects of irrigation projects:
* Is there adequate water for the project,
either from precipitation
(rainfall), surface water, groundwater,
or aquifers?
* Are cycles of floods and droughts
accounted for in the project
design?
What would be their impacts on the project when
they occur?
* Does the project design minimize surface
runoff that might
carry away valuable nutrients and
topsoil and cause pollution
downstream?
* Do upstream resource uses (construction
and forestry
activities) affect the quality of the
water to be used by the
project?
* Will the project involve
irrigation? If so, the planner should
be particularly careful to assess the
impact of the project
downstream and the possibility for
increasing habitat for
aquatic pest insects including vectors
of waterborne diseases,
and abundance and quality of the project
water source.
* Will the project affect water-flow
patterns of the area?
Would these alterations affect the water
supply needed by
other users?
* Are malaria, yellow fever,
schistosomiasis, or other waterborne
diseases carried by organisms associated
with water,
prevalent in the region?
And will the project in any way
result in increased incidence of the
diseases?
* Will the project reduce downstream water
flows and thus
affect fisheries, aquaculture projects,
the growth of aquatic
weeds, the habitat for mosquitoes and
other vectors of
disease-causing insect pests?
* If habitat is increased for disease
vectors, could this result in
increased use of insecticides or
molluscicides with the possible
result of chemical poisoning of fish and
water supplies?
* Could irrigation cause waterlogging of
the soil?
* Is the soil susceptible to salinization?
* Does the soil have a characteristically
high pH and could
irrigation result in soil
alkalinization?
* Does the site have lateritic soil or is
laterization a potential
problem?
(See Chapter 5).
* Will new wells be sunk?
If so, could this affect the water
table?
* If the water table is affected how will
stream levels and
wetlands be affected?
* Is the project site near the sea?
If so, could lowering the
water table allow salt water to intrude,
contaminating
freshwater supplies?
* Could downstream water or groundwater
quality be affected
by high salinity in the return flows
from the project site?
* What other water supply and management
options should be
considered?
* What alternative designs could minimize
possible water
supply impacts?
Other appropriate questions may be
added. By considering
these
questions, the trade-offs necessary to minimize the negative
affects of
the project can be evaluated.
WHAT ALTERNATIVES EXIST
A number of practices are available to
reduce the amount of
water used
for irrigation (and thus decrease possible negative impacts)
or to
conserve water. These management
methods can be
used to
lessen water loss from runoff, evaporation, deep percolation,
irrigation,
and stored soil water. Practices are
also available to
maximize the
efficiency of irrigation and the use of stored soil water:
- control of runoff losses through contour
tillage, terracing, use
of crop residues, and water spreading
(the diversion of
surface runoff to sites where the water
infiltrates and is
stored in the soil)
- control of evaporation losses through
mulching
-
reduction of deep percolation through the use of horizontal
barriers (i.e., asphalt)
- conservation irrigation such as drip
irrigation (See Appendix
A for references)
- water harvesting (i.e., through
construction of small ponds to
capture excessive water during rainy
season)
- use of drought tolerant crops
- no-tillage agriculture (see Chapter 5)
- relying on summer fallows for dryland
farming areas currently
being irrigated
There are also several ways to avoid or
mitigate negative
effects of
irrigation on human health. When canals
are used, people
can take
extra care to draw water from uncontaminated stretches of
the canal, or
from safer sources such as deep wells if such possibilities
exist.
If alternative waste disposal methods are
adopted, disease
organism life
cycles can be interrupted, preventing the spread of
disease.
More research on the natural enemies of
snails and mosquitoes
can identify
possible predators such as ducks, geese, or fish.
There may
also be local plants that serve as molluscicides, such as
the soapberry
(berry of the dodecandra plant in Ethiopia).
The best
method may be
to deprive disease vectors of a suitable habitat by
conveying
water in pipes or tile aqueducts and by using buried tiles
to drain
excess water from fields. On a small
scale, the use of
enclosed
systems for irrigation would not only protect humans from
disease but
would also prevent seepage and evaporation of water
used for
irrigation. However, these solutions
may be costly or
beyond the
control of small-scale project operators.
CHAPTER 7
SOIL NUTRIENT MANAGEMENT
Nutrients, such as Nitrogen (N),
phosphorus (P), potassium (K)
and others,
are essential to plant growth. Planners
of agricultural
projects
should have an understanding of the dynamics and cycles of
nutrients in
the natural environment in order to devise wise soil
nutrient
management plans. Understanding the
inputs and outputs
of nutrients
in a crop field will help in devising techniques that keep
a good
balance of nutrients in the soil. For
example, the figure
below
illustrates how nitrogen is added and withdrawn from the soil
through the
nitrogen cycle.
<THE
NITROGEN CYCLE>
03p75.gif (437x437)
SOURCES OF PLANT NUTRIENTS
In crop lands there are six primary
sources of nutrients:
natural soil
fertility, plant residues, animal waste, legumes, water,
inorganic
fertilizers.
Natural Soil
Fertility
All cropland has a degree of natural soil
fertility. Soil fertility
refers to the
inherent capacity of a soil to supply nutrients to plants
in adequate
amounts. Some soils, such as the flood
plains of rivers,
are usually
very fertile. On the other hand, loose
sandy soils, which
contain
little or no organic matter, and usually not very fertile.
<NITROGEN
PRODUCTION FROM CROP RESIDUES>
03p76.gif (600x600)
Organic
Matter
The
Significance of the C/N Ratio. There is
a close relationship
between the
organic matter and nitrogen content of soils, expressed
as the ratio
of Carbon to Nitrogen or C/N. C/N is
important in
controlling
the available N and the rate of organic decay in soils.
The
relationship
of these two elements in organic material added to the
soil is
crucial for two reasons: a) Keen
competition among micro-organisms
for available
N results when added crop residues have a
high C/N
ratio (more carbon in relation to nitrogen).
This means the
rate of
decomposition will be faster and the availability of nitrate to
plant will be
depressed until the activity of decay organisms slows
down.
b) Because the C/N ratio is relatively
constant in the soil, the
organic
matter content of the soil depends largely on the nitrogen
level.
The figure above shows the trend to be
expected when
materials
with high and low C/N ratio are added to the soil.
Plant
Residues. Leaves, roots, and other
plant debris build up the
soil
structure by providing organic matter.
As these materials
decompose,
nutrients are released. The amounts of
nutrients vary
greatly
depending upon the type of plant, temperature, rainfall, and
whether the
material is plowed into the topsoil or not.
Animal
Wastes. Animal wastes such as manure
are organic matter
that may
decompose to provide nutrients to the soil.
Manure has
been used as
fertilizer for centuries and is useful and environmentally
sound, if
excessive amounts are not used.
The nutrient content of manure depends
upon the animal, the
type of feed
given, and the amount of water consumed by the animal.
Disease
organisms that affect humans can be carried in animal
excrement,
therefore, only manure from healthy animals should be
used.
Extra precaution is necessary when using
animal manures if
these
diseases are a problem in the area.
Local authorities usually
are aware of
these problems and can provide information.
Aerobic
composting,
as discussed below, can kill the pathogenic bacteria, eggs
and spores
found in animal manures. Other
by-products that may
be used for
fertilizer are bone meal, blood meal, and fish meal.
Cover new manure as soon as possible and
mix it with the soil.
As much as
1/4 of the nitrogen content can be lost in one day due to
ammonia
volatilization if the manure is not handled properly.
Temperature and moisture affect
decomposition of manures.
Therefore
timing of the application of manure may vary with climatic
zone.
In a semi-arid area, for instance, where
high temperatures are
coupled with
high aeration of the soil, manure applied too early
before the
onset of rains, can lose a large part of its nutrients from
rapid
oxidation of the organic matter.
NUTRIENT CONTENT OF ANIMAL
MANURES
Animal
% of Dry Weight
N P
K
Dairy
Cattle
2.4 0.6
3.0
Beef
Cattle
2.0 0.8
1.7
Poultry
3.7
1.7
1.9
Swine
5.9
2.5
4.1
Sheep and
Goat 3.0
1.1
4.8
Legumes.
Legumes, including peas, beans, groundnuts,
and alfalfa,
contain
nitrogen-fixing bacteria in their root systems.
These plants
fix nitrogen
from the air into proteins that become available to the
plants when
the bacteria die. Bacteria can fix
enough nitrogen to
support a
grass and legume meadow if no other nitrogen source is
available.
The nitrogen usually is produced as the
plant needs it.
Plants with
poor growth will not fix much nitrogen.
If there is a
high level of
nitrogen available in the soil, the bacteria fix less.
Nitrogen then
is not a limiting factor.
Legumes are often grown in association
with other crops in
intercrop or
crop rotation systems to provide nitrogen for other
plants.
For example, peas or beans are often grown
with maize in a
mutually
beneficial system. Such multi-cropping,
or polyculture
practices can
reduce or eliminate the need for chemical fertilizers.
It
is important
to exploit the ability of the cropping system to reuse its
own stored
nutrients. In complex crop mixtures,
closed canopies and
larger root
areas usually promote nutrient conservation and cycling.
In addition to their compatibility in the
field, maize and
legume
combinations complement each other nutritionally.
By eating
both, human
beings can receive nearly their complete protein requirements--without
adding meat
or dairy products. Other plants
have similar
relationships, both symbiotic and nutritional.
Often,
traditional
crop patterns adapted by local farmers turn out to be the
best use of
the land as well as the best combination for providing
essential
proteins for human diets. Development
workers planning
to introduce
new species should consider the potential of indigenous
crop mixtures
as a starting point for the design of soil management
practices.
In combination with other crops grown
locally, indigenous
crop mixtures
can provide adequate nutrition and even improve local
diets.
Precipitation
and Run-on Water
Rainfall can provide nitrogen and
phosphorus to cropland, but
in very low
amounts compared to other sources. The
nutrient
content of
precipitation is influenced by the weather, and by the
presence of
industry, cities, disposal sites, power plants, feedlots, etc.
For example,
phosphates, that may be present in dust, ash or smoke,
are made
available to plants when dissolved in rain.
Nutrients in soil and organic matter that
are suspended in
run-off
water, that is, eroded and carried from elsewhere, may be a
significant
input in certain situations. For
example, rice-growing
areas subject
to inundation or flooding from silt-laden rivers or
riverain
cropping systems that involve planting on previously inundated
land, may
have sufficient nutrients from this source when the
seasonal
river flow declines.
Inorganic
Fertilizers
Inorganic fertilizers consist of chemicals
with little or no
organic
matter. Chemical fertilizers supply
nutrients that are
readily available
after application, in amounts and ratios that are
more readily
controlled.
Inorganic fertilizers are expensive, often
unavailable, and
generally do
little to improve the structure of the soil.
Many farmers
have
difficulty calculating how much chemical fertilizer to apply.
This can lead
to under-fertilization or over-fertilization either of
which do not
produce desired results. Many tropical
soils cannot
hold the
chemical nutrients long enough for the plants to use them.
Often the
first rain washes them out of the soil.
However, in some
areas organic
fertilizers are not available or not in sufficient quantities.
In that case,
correct application of inorganic fertilizers is
necessary and
critical.
EVALUATING THE SOURCE OF NUTRIENTS
The choice of nutrient source depends on
the situation. Even
soils that
are naturally very fertile may be depleted of nutrients by
continuous
cropping.
The need for fertilizer, i.e., anything
added to the field to
increase the
natural fertility of the soil, depends on:
- ability of the soil itself to provide
essential nutrients to
crops (soil fertility)
- nutrient demands of the crops
The choice of
fertilizers depends on availability, costs, and the
fertilizer's
effect on the soil. Whether nutrients
are organic or
inorganic
does not matter to the plant. Plants
can use fertilizers
from any
source. However, other effects of
inorganic fertilizers are
often
unknown. In the long-term perspective
they can reduce the
diversity of microbes
in the soil. They may also be hard to
obtain
and/or
expensive. Wherever possible it is best
to use organic fertilizer.
Potential
organic fertilizers exist wherever there are animal
and plant
wastes. They are relatively cheap
although they require
larger inputs
of labor. They have the added advantage
of contributing
organic
matter to the soil. In the warmth and
moisture of the
humid tropics
most soils are very highly weathered, sandy, and
coarse
textured. In such highly weathered
soils, organic matter, in
addition to
adding nutrients to the soil, plays a very dynamic role in
the colloidal
complex that holds nutrients and retards leaching.
In
these soils,
organic matter decomposes rapidly so that its nutrients
are available
quite quickly. One of the best
practices for fertilizing
with organic
materials is composting.
<ELEMENTS
OF A COMPOST PILE>
03p81.gif (486x486)
Composting
Composting is a natural process whereby
organic wastes are
microbially
decomposed. It has the following
advantages:
- uses waste material and is of low cost
- can yield organic matter for fertilizer
within several weeks,
depending upon the ingredients used, the
climate, and so
forth
- generates heat sufficient to kill insect
eggs, larvae, weed
seeds, bacteria, and other pathogens
that may cause human
disease
- stabilizes the volatile nitrogen
fraction of manure by fixing it
into organic forms
- the final product is easy to store and
handle
Composting also has some disadvantages:
- is labor intensive to produce
- requires space to store
- requires water
- is bulky and less convenient to
transport and handle than
solid inorganic fertilizers
- is dependent on supplies of manure and
organic matter
- is more feasible for smaller areas, such
as, kitchen gardens
or small plots
In many countries, composting in some form
or another is
practiced
traditionally. Examination of local
methods can provide
good
guidelines for project planning in terms of available ingredients,
length of
preparation time, receptivity of residents to the practice,
and so on.
CHEMICAL COMPOSITION OF SOME
COMPOST MATERIALS
Carbon:nitrogen
----- kilos/ton-----
Material
Ratio
N
[P.sub.2][O.sub.5] [K.sub.2]O
Grass
Hay 80:1
9-11
2-5
11-16
Legume
Hay 12-24:1
20-27
5-7 16-21
Straw
75-150:1
5-9
1-3 9-14
Cow Manure
& Bedding 15-25:1
3
.5 2
Seaweed
19:1
.5 .35
2
Human
Faeces 5-10:1
2-3
1-2
.5-.9
Sugarcane
Fiber 200:1
.11
.01
+
Filter
Mud 22-28:1
.5
.9 .05
Maize
Stalks 60:1
-
- -
Fish
Scrap -
1-3
.9-3 -
Vegetable
Wastes 12:1
- -
-
Groundnut
Shells -
.35
.06 -
THE EFFECTS OF FERTILIZERS ON THE
ENVIRONMENT
Both fertilizers and naturally occurring
nutrients are subject to
all the
natural processes that tend to reduce nutrient levels--leaching,
runoff, and
erosion. In addition, other sources of nutrient loss
in
agricultural systems are:
- nutrients in the crop material that
leaves the farm
- nutrients in stock or stock products
that leave the farm
- leaching of nutrients below the root
zone
- loss of nitrogen to the atmosphere
through volatilization
(escaping as a gas) or through burning
of vegetation or crop
residues
- losses through run-off water (erosion)
If these processes can be halted or
slowed, the chances are
greater that
the nutrients present in the soil and those applied in
the form of
fertilizers will remain available for plant growth.
Ensuring
that
nutrients remain in the soil for crop use lessens the likelihood
of excessive
nutrients entering the larger environment and thus
causing
pollution.
<LEACHING>
03p83.gif (486x486)
Leaching
Leaching is the process by which soluble
chemicals move downward
through the
soil in water that is percolating through the soil.
Nitrates are
the most easily leached nutrients and are commonly
found in
drainage waters. Leaching from cropland
depends upon the
type of crop
grown, as well as the soil type and its drainage characteristics,
and on the
amount of available water passing through the
crop root
zone. Leaching effects are particularly
important early in
the rainy
season in the humid and subhumid tropics, when the main
flush of
mineralization of soil organic matter occurs.
Under perennial
crops with
permanent, deep root systems, leaching is of minor
significance.
Runoff
Runoff occurs when it rains so hard and
fast that the ground
cannot absorb
the moisture fast enough. When
fertilizers are left on
the soil
surface, the first rainfall can carry away a substantial
portion of
the nutrients. Fertilizers during
periods of light rains
move into the
soil dissolved in the available water.
The loss of
fertilizer
may be much less if the fertilizer is incorporated into the
top few
inches of the soil before rains begin.
Being soluble, nitrates
are easily
leached into the soil. The
concentration of nutrients in
runoff water
will vary greatly from field to field, depending upon soil
characteristics,
slope, crops grown, type of manure or fertilizer used,
and rainfall
conditions. Organic fertilizers mixed
with the soil can
increase the
soil's capacity to absorb water.
Erosion
Although sediment transport through
erosion depends upon the
volume and
velocity of water flow, it can be the major transport
process for
phosphorus and organic nitrogen clinging to or adsorbed
on sediment
particles. When the velocity of water
is reduced, the
large
particles of sediment fall out of solution.
The remaining
sediment is
usually finer and has a higher capacity (more surface
area to which
to adhere) to adsorb phosphorus, so that transported
sediment is
richer in phosphorus and nitrogen than the original soil.
Organic matter is often transported along
with sediment, causing
further
nutrient losses from the fields.
Nutrient losses from
cropland can
be controlled by proper management practices such as
those
described in Chapter 5 for sound erosion control.
For example, leaving plant residues on a
field can reduce
erosion rates
of 25-65 tons/hectare/year to 12.5 tons/hectare/year, and
at the same
time provide nutrients to the field and thereby reduce
the need for
inorganic fertilizer. Other soil
management/erosion
control
methods, such as crop rotations with sod, contouring, and
terracing,
can reduce nutrient losses as well.
THE EFFECTS OF MOVEMENT OR LOSS
OF SOIL, NUTRIENTS
Nutrients, including fertilizers, in
solution or suspension in the
groundwater
or surface water bodies, can result in two problems:
* Nutrients may reach toxic levels and
become a health hazard
to humans and animals.
* When added to water systems (i.e.,
ponds, small lakes),
nutrients may accelerate the
eutrophication rate to the
extent that it becomes harmful to the
environment.
Eutrophication
Eutrophication is the enrichment of a body
of water by nutrients
with
resulting increases in growth of aquatic plants.
When
nitrogen and
phosphorus enter the water in high levels as a result of
runoff or
other transport methods from agricultural lands, over-fertilization
of the water
systems stimulates an exploding growth of algae
populations.
Algae can:
- cause taste and odor problems
- create obnoxious conditions in
impounded water such as
small ponds
- block passage of the sun's rays and
interfere with photosynthesis
of bottom vegetation
- clog the screens of water treatment
systems
When these
massive algae populations suddenly die off, their decomposition
releases
gaseous substances and depletes oxygen levels in
the water,
with harmful effects to fish and other aquatic organisms.
Health
Effects
Fertilizers usually contain nitrogen,
phosphorus, and potassium.
Of these,
nitrogen in particular has been associated with
health
problems. Nitrogen, which occurs as
nitrites, nitrates, and/or
ammonia, may
be converted to another form by chemical reactions
occurring
naturally in the environment.
Nitrites.
The nitrite form of nitrogen is very toxic;
if taken by
humans in
drinking water or in food, it enters the bloodstream
where it
interferes with the ability of the blood to carry oxygen.
Nitrites can
also combine in compounds that may cause cancer in
humans.
Nitrates.
Nitrates are much less toxic than
nitrites. Healthy,
mature
animals with single stomachs are able to expel nitrates in
their
urine. However, cattle, young animals,
and children can
convert some
nitrates to nitrites in their stomachs, a condition that
can be
harmful.
Both nitrites and nitrates occur naturally
in foods and water,
but only in
small amounts. Only small amounts can
be tolerated by
humans.
The World Health Organization has fixed the
Drinking
Water
Standard for nitrates at 0 to 50 parts per million (ppm) as
recommended
levels, and 50 to 100 ppm as acceptable.
In many
developing
countries, however, these levels are exceeded, especially
where
drinking water supplies are contaminated by nearby concentrations
of nitrogen,
such as manure piles in farm barnyards.
Obviously project plans must include
consideration of fertilizing
practices in
terms of the location of compost piles, manure accumulations,
and slope of
fertilized fields in relation to housing and water
supply.
Ammonia.
Ammonia, like nitrate, can be converted by
specialized
bacteria to
toxic nitrite. Ammonia occurs
naturally. It is generated
by
micro-organisms as they break down organic matter on the
bottom of
stagnant lakes. Dissolved ammonia can
occur at levels
that are
toxic to fish. Another problem with
nitrogenous fertilizers is
that the
addition of a common fertilizer, sulfate of ammonia, may
acidify an
already acid soil. However, this may
benefit a basic soil.
Phosphorus.
Phosphorus usually enters water as a soluble
phosphate
compound that
is completely available for algae growth.
Phosphate
may also
enter the water adsorbed on sediment or on particles of
organic
matter. The phosphates are then slowly
released. These
phosphates
then contribute to problems associated with eutrophication.
MANAGEMENT OF NUTRIENT-RELATED FACTORS
Erosion control practices may be an that
is needed to control
the loss of
phosphorus and nitrogen. If nutrient
losses persist,
however,
other nutrient management practices may be necessary
such as
fertilizer management, crop rotation, legume cropping etc.
One must be careful that solving one
problem does not create
another. As
an example, in certain areas of the state of Texas, USA,
terraces were
built to retain moisture. While the
terraces did hold
water, this
moisture control caused nitrate leaching, which contaminated
the
groundwater supplies of the area.
Managing
Fertilization
To prevent the build up of nutrients in
soil and their subsequent
loss through
leaching, farmers should apply only the needed
amount of
fertilizer to croplands. Failure to
estimate fertilizer
requirements
accurately leads many people to over-fertilize.
The best
way to
prevent overfertilization and the leaching that results is to
estimate the
need for fertilizers and apply only that which will be
used by the
crop. The table below provides general
guidelines for
the nitrogen
requirements of selected crops. It
should be kept in
mind,
however, that most of these generalizations must be evaluated
for each
locality.
GENERAL CROP NITROGEN
REQUIREMENTS
Kilos of nitrogen
Crop
per hectare per
year
Grass (2-3
times as a top dressing) 100-150
(maximum)
Small
grains 20-
40
Potatoes
120-160
Leafy
vegetables 120
Root
crops 80
General home
vegetables 100
Symptoms of lack of fertilizer will emerge
when the seedlings
are a few
inches tall. Fertilizer can be applied
at this time in
between the
rows. At this point, when the soil is
deficient in a
particular
nutrient, the crop plants will develop
specific symptoms.
Thin stems
and yellowing of leaves is typical of nitrogen deficiency,
whereas
purpling of leaves signals phosphorus deficiency.
The effects
of some
elements are greatest when fertilizer is applied near the
time of
fastest vegetative growth, that is, several weeks after the
plant emerges
from the soil. This is not true for
phosphorous, which
needs to be
applied early for root development.
With late application,
less
fertilizer is used and it is used more efficiently.
However,
late
application can set back development of the crop.
One practice
is to put
half the fertilizer on the field at one time early in the
growing
season and the rest later.
Soil fertility and physical conditions may
be estimated by
observing
certain biological indicators such as the prevalence of
specific
weeds. Although weed growth may be
determined by more
factors than
just soil conditions, at times the dominance of one
specific weed
species can be well correlated with salinity, drainage,
nutrient
levels, or soil texture characteristics.
The development
worker is
advised to consult local farmers, extensionists, or technical
experts to
interpret the indicators.
Project planners who are not agricultural
experts will probably
want to
consult others for advice on actually choosing fertilizers and
using them in
crop production. Local farmers,
extensionists, and
agricultural
experts have experience in determining what kind and
how much
fertilizer is needed.
Crop
Rotations
The average amount of fertilizer needed on
fields often can be
reduced by
rotating crops. Crops that require high
nitrogen levels,
such as
maize, sorghum, and cotton, can be rotated with legumes
such as
soybeans, beans, or alfalfa, or with crops that require
smaller
amounts of nitrogen such as small grains.
Crops can be
alternated by
growing season to reduce the need for other fertilizers.
The
particular cropping sequence appropriate in a rotation will vary
with the
climate, soil, tradition, and economic factors.
Some crop
yields are
affected by the previous crop. For
example, yields of
almost any
crop after barley are usually lower than after corn,
soybean or
wheat.
<CROP
ROTATION>
03p89.gif (486x486)
Animal Wastes
Animal manures can be good fertilizers,
but there are problems
associated
with them. If manure is applied as it
becomes available
nitrogen will
be released slowly before planting.
This is not always
possible.
Storing manure, however, is difficult and
costly. It is also
difficult to
determine how much nitrogen is being applied when
animal wastes
are used, especially since the nitrogen amount varies
with the
animal and its diet. The best way to
use animal manures
to prevent
nitrogen loss to volatilization is to plow it into the soil
directly, or
add it as a slurry, so that it soaks into the soil.
One of
the
advantages of animal wastes as fertilizers is that they release
nitrogen
slowly enough that little is lost through leaching.
Plowing-Under
Green Legumes
Before chemical fertilizers were
developed, many farmers would
grow a legume
on a field and then plow it into the soil to serve as a
nitrogen
source for later crops. The main
disadvantage is an economic
one--no crops
can be harvested from the field that season.
However,
compared with the cost of using chemical fertilizers and
their
potential impacts upon the environment, this practice is useful
when a farmer
has enough land to leave fields fallow.
In areas
where
chemical fertilizers or animal wastes are not available, this is
one way to
add nitrogen and organic matter to the soil.
In general,
immediate
benefits from incorporation are only observed with young
legume green
manures. Most other residues have high
C/N
(Carbon/nitrogen
ratio, see beginning of this chapter for explanation)
and
"tie-up" nitrogen during a period of time.
Controlling
Surface Applications
The type of fertilizer must be chosen
carefully, and it must be
applied at
the right time. For example, nitrogen,
which moves
quickly
through the soil, should be applied just before or during the
growing
season. Phosphorus and potassium
fertilizers can be applied
after the
growing season or sometime before the next one.
It is
usually best
to mix fertilizers into the soil right after application to
reduce loss
of nutrients to erosion.
THE EFFECTS OF NUTRIENT MANAGEMENT
By answering questions such as those below
for each project
and site, the
development worker can estimate the potential effects
of
fertilization projects on the environment.
If the answers are not
readily
apparent, go back and think about the project site again.
Consult local
experts in the field if the answers point out major
problems.
Use the questions as guidelines to plan
projects that will
be both
environmentally sound and successful.
* Is manure available for use as a
fertilizer in the project? If
used, would this practice result in the
spread of weeds
and/or disease through human contact
with the manure?
* Will plant residues be used for
fertilizers and soil structure
enhancement?
What is the C/N ratio of these materials?
* Will new plant species or varieties be
introduced? This could
have long-term environmental
repercussions and the potential
effects should be carefully reviewed.
* Could the new species out-compete
traditional crops in the
region?
* Do the new varieties need more
fertilizer than traditional
crops?
* Will the new varieties require more
pesticides, and/or the
use of heavy farm machinery, which could
lead to other
problems?
* Could new pest species be attracted into
the region along
with the new crop?
* Will the project involve the use of
inorganic fertilizers?
* Could this practice lead to nitrite
toxicity for people or animals?
* Are precautions being taken to avoid
over-fertilization?
* Could the project enhance loss of
nutrients via runoff,
erosion, or leaching?
* Could nutrient transport cause
eutrophication?
* Are there other nutrient management
considerations?
* Does the success of the project depend
on inorganic fertilizers?
If so, do farmers have a reliable
source? Have they
been trained in its use?
What are the projected costs of
fertilizers?
* What alternative project designs could
be used at the site to
minimize nutrient loss?
ALTERNATIVES FOR NUTRIENT CONTROL
The following table lists ways to manage
nutrients in agricultural
projects.
The left-hand column names the practice; the
right-hand
column describes the advantages, disadvantages, and
potential
effects of each as a nutrient control method.
CONTROL OF NUTRIENT
LOSSES
Practice
Advantage/Disadvantage
Timing
nitrogen application Reduces nitrate
leaching; increases efficiency
of nitrogen
use. However, may
encounter labor
shortages.
Rotating
crops Reduces fertilizer
requirements; reduces
erosion and
need for pesticides. But may
decrease
production of saleable crops.
Eliminating
excessive Reduces cost of
fertilizers; can cut nitrate
fertilization
leaching.
Using animal
wastes Enables slow release
of nutrients; economic
gain for small farms; improves soil
structure;
extends the period of residual
effects of
applied nutrients on subsequent
crops.
However, there are labor costs and
problems with
spreading.
Plowing under
green Reduces need for
nitrogen fertilizer; not
legume
crops always feasible;
amounts of nitrogen difficult
to determine;
ties up available land.
Controlling
fertilizer May decrease nitrate
leaching; not yet
release
time economically
feasible.
Incorporating
surface Decreases nutrients in
runoff; may add
applications
costs; not always possible;
no effect on
yields.
Timing
fertilizer plow-down Reduces erosion
and nutrient loss; may
not be
convenient.
Source:
U. S. Department of Agriculture, 1975.
Adapted from
Control of Water from Cropland, Vol. I, A Manual for
Guideline
Development.
CHAPTER 8
PEST MANAGEMENT
"Pest" is a human-oriented
term. It has been defined as "an
organism that
reduces the availability, quality, or value of some
human
resource. This resource may be a plant
or animal grown for
food, fiber,
or pleasure (or) a person's health, well-being, or peace of
mind."
(Gips 8.8, Flint 8.7)
What is considered a "pest" then
is
based on
human needs and values and thus can change from situation
to
situation. Most organisms and animals
are not pests and are
considered
beneficial.
The use of chemicals that control pests
and herbs developed in
the 1940s and
accelerated in the following decades.
The use of
pesticides
and herbicides has now spread throughout the world.
It is
only in the
past twenty-five years that the horrors of using pesticides
have become
known and documented. Balancing against
the great
benefits that
pesticides and herbicides offer is the negative impact of
direct
contact in applying the chemicals, and of secondary effects on
humans
through the water, food, and meat that we eat, as well as
damage to the
environment.
Pests, however, are a particular problem
in farming systems.
Changes in
cropping systems often lead to changes in the numbers
or kinds of
pests and associated natural enemies (predators and
parasites) in
the agricultural ecosystem. Planning
environmentally
sound
agricultural projects requires looking beyond the types of pests
and predators
present and considering how measures used to control
pests will
affect the total ecosystem. Too often
failure to take this
broad
approach has resulted in damage to the environment and in
less than
successful projects.
In many agricultural projects, pests are
controlled only by the
use of
chemical pesticides. Some chemical
pesticides, however, cause
environmental
problems as a result of their toxic or residual effects
and are a
cause of sickness and death to humans.
In a small-scale
project, it
may be possible to control pests by using less damaging
alternatives
such as promoting biological control, planting different
crop
mixtures, using less persistent and less toxic pesticides, finding
more
species-specific pesticides, or growing resistant crop varieties.
It should be
recognized, however, that some alternative methods
require more
sophisticated management.
<PEST
POTENTIAL RELATED TO CROPS>
03p95.gif (534x534)
Some birds and rodents if they reach pest
proportions can
cause great
damage and losses in agricultural systems and thereby
significantly
reduce the amount of food available for people and
livestock.
Various methods can be used to control
pests--from scarecrows
and netting
to trapping and killing them individually.
It is
more common,
however, to poison these animals, even though poisoning
is
potentially a far more dangerous practice to people and other
non-target
organisms. Whenever possible, trapping
and other mechanical
control
practices should be used to control larger pests.
When properly
managed, the pests that are edible can provide an
important
source of protein and income to local people.
ENVIRONMENTALLY SOUND PEST
MANAGEMENT PRACTICES
The best way to lessen or avoid unwanted
environmental
effects from
pesticide use is to minimize their use.
Feasible alternatives
to pesticides
often exist and should be investigated by the
development
worker. For example, there may be
combinations of
local plants
that can control pests. In some areas,
the use of resistant
varieties and
delayed or early planting can reduce crop damage
by
pests. It is important for the
development worker to understand
how to use
alternative control methods. In the
long run, it may be
better to
protect and enhance the natural predators and parasites of
pest species
than to use chemical pesticides. Insect
pests can become
resistant to
certain pesticides and may do so after only a few applications.
Predator
species, on the other hand, may have longer
life-cycles
and may be more sensitive to repeated pesticide applications.
Find out what
kinds of pests are a problem before using a
pesticide and
try to use pesticides that are both species-specific and
short-lived.
Broad spectrum pesticides kill beneficial as
well as pest
organisms and
are not recommended. Also find out what
other
pesticides
are being used locally to control disease vectors or other
pests.
If pesticides are already in use some
resistance may already
exist among
pest species.
If possible consult local specialists and
authorities before deciding
on a
particular pesticide for use on agricultural lands.
Some
countries
have very specific laws governing the use of particular
pesticides,
and these should be taken into account before any time or
money is
spent obtaining or using chemical pesticides.
Some countries
outlaw
certain pesticides and export them to other countries.
Contact
government agencies and local universities or the regional
office of the
Pesticide Action Network (PAN) for information on local
pest species
and alternative control practices. A
list of regional
offices of
the Pesticide Action Network (PAN) that can provide
technical
information or answer specific questions is in Appendix B.
Because of the potentially harmful effects
of chemical pesticides,
development
workers should take care to investigate alternative
measures and
use them wherever possible.
ALTERNATIVES TO PESTICIDES
Local Plants
Many farmers know the plant species in
their area that have
insecticidal
properties. There are about 1,600 plant
species known to
possess
pest-control properties. Try to find
indigenous plant materials
and use them
rather than chemical pesticides. Two
such plants
with
insecticidal properties are tobacco and pyrethrum (derived from
chrysanthemums).
Both are now widely distributed throughout
the
tropics.
Another plant used is the derris root.
It produces a chemical
called
rotenone which is used as a poison especially for ridding
fish ponds of
trash fish. Some plants, like the neem
tree have
multiple
types of pest-control action. When a
local plant which has
insecticidal
properties is pointed out, try making a solution from
crushed
leaves or stems and spray it on a small test area.
If this
seems
successful, it may be cheaper to use than commercial pesticides,
easier to
get, and environmentally safer. Even if
the test is
not
successful there may be other ways of utilizing the tree or plant
for
pest-control. Local farmers often have
this information.
Crop
Management Practices
Rotation.
Crops usually are rotated for economic and
nutrient
management
reasons. Crop rotation also can be used
as a method to
control
insects, weeds, and plant diseases.
Many traditional agricultural
practices
rely upon crop rotations to provide weed, disease and
insect
control. Crop rotations, including
non-host crops, have proven
effective
against soil-borne pathogens (cabbage black rot, bean bacterial
blight) and
corn rootworms and should be explored with local
experts, and
with local farmers who rotate their crops.
Resistant
Varieties. There are also crop
varieties that are resistant
to attack by
disease or insects. These varieties
sometimes need the
help of
pesticides, but in greatly reduced quantities.
Intercropping.
Intercropping and polyculture can also
reduce the
spread of
pests and disease organisms. By
interspersing non-susceptible
crop plants
with host plants in the same field, the spread of the
pest and
disease organisms among susceptible crops can be considerably
reduced.
Moreover, the intercrop may also provide a
more
favorable
habitat for the growth and reproduction of pest and disease
organisms
than the primary crop. It may also
provide habitat for
beneficial
insects and other organisms. For
example, alfalfa strips
interplanted
among cotton rows attract lygus bugs away from cotton,
avoiding
damage. Surrounding melon or squash
fields with a few
rows of corn,
acts as a trap crop for melon flies.
Planting
Time. Another crop management practice
is to change
planting
times to prevent attack by insects and disease.
Insect
reproduction
cycles are often attuned to the growth of plants.
If
crops can be
planted a few weeks before or after the normal time,
farmers may
be able to by-pass the stage of the insect that causes
the most
damage to the crop. Early maturing
varieties may escape
insect
attack.
Early planting can be effective in
avoiding the egg-laying
period of a
pest by allowing crop maturation before pest attack
occurs.
However, because it requires knowledge of
insect species and
their life
cycles, the advice of entomologists or other scientists from
local
universities and government agencies may be needed.
Plant
Spacing. Modifying the spacing of crop
plants by decreasing or
increasing
plant densities may provide a measure of pest control by
affecting the
micro-environment of the pest, the vigor of the plant,
and the
duration of crop growth. For example,
densely planted
stands of
grain crops suffer less from chinch bug attack, whereas
narrow-row
planting of cotton can discourage boll weevil infestations.
Destruction
of Alternate Host Plants. It may be
found that the crop
pests are
breeding or spending part of their life cycle on another
plant
species. If the alternate host is
another crop, it may be best
not to grow
both in the same area. If the alternate
host is a weed,
it may be
possible to control it and thus reduce the pest population.
Control of
the sugar beet curlytop virus involves destruction of the
Russian
thistle, the alternate host of the insect vector, the beet
leafhopper.
Many weeds, however, especially flowering
Compositae
(sunflower
family) and Umbelliferae (carrot family), can provide
alternate
food (pollen, nectar) to a number of important parasites
and
predators. For example, biological
control of crickets in Puerto
Rico depended
on the presence of two weeds that provided nectar to
the parasitic
wasps. In this case, it was desirable
to have more
weeds of this
type. On the other hand, if a certain
type of crop is
preferred by
a pest, one way to control the pest is to plant that crop
along with
the desired crop and sacrifice the alternate crop that
serves as a
trap to the pest. Pests and diseases
can also be controlled
by growing,
in sequence or rotation, crop plants that are not
susceptible
or do not constitute alternative hosts.
Mechanical
and Traditional Control Practices
Sometimes the easiest, least costly, and
most environmentally
sound means
of controlling pests on agricultural lands is by using
mechanical
and traditional control methods. Some
of these methods
for weed
control, for example, involve:
- pulling weeds by hand or cutting them
down
- covering weeds with mulch to prevent
growth
- burning a field prior to planting
- flooding the field
- normal tillage practices such as plowing
and harrowing
Mechanical and traditional practices can
be very effective in
those
countries where labor is available and money and pesticides
are not.
For example, insects can be killed by
trapping; rats can be
smoked out,
trapped or clubbed; and birds can be shot or trapped in
nets and
removed from the field. Hunting and/or
simply shooting
nuisance
birds or game animals can also be effective.
Biological
Control Methods
Pests can be effectively controlled by
supporting the resident or
introduced
natural enemies of pests. Many of these
methods are
"new"
as far as research is concerned.
However, in agricultural
areas that
retain a diversified environment, biological control is an
everyday occurrence.
Birds eat insects, cats eat birds, and so
on.
Each predator
has its prey and helps control the population of that
prey.
In practice, biological control is the use
or encouragement of
natural
enemies for the reduction of pest organisms as well as
introducing
crop varieties that are resistant to pests discussed
earlier.
Natural enemies act as mortality agents
that directly respond
to the size
of the population. Thus natural enemies
act as density-dependent
factors.
This relationship between pest density and
the intensity
of attack by natural enemies is called a functional
response.
For density-dependence to happen in
agroecosystems it is
necessary to
let the insect pest population build up sufficiently to
stimulate the
corresponding build-up of the beneficial predator or
parasite
population. This will not happen if
pesticides are used on
the pest as
soon as it appears. Thus, a certain
amount of injury to
the crop may
occur. A small test plot may
demonstrate the effectiveness
and the
negative possibilities before introducing the technique
widely.
Observation and discussion with farmers can
help to determine
the maximum
pest population that can be tolerated at a
particular
time without crop damage becoming too serious before
other
controls are sought. Natural controls
may take over before
this happens.
Research into the use of biological
suppression controls has
expanded to
include other methods, including the use of sex attractants,
insect growth
regulators, sterilized male insects, repellants,
and warning
or aggregating chemicals (pheramones) that influence
the behavior
of insect colonies. These methods have
worked well in
some
small-scale applications but may or may not work in other
situations.
They should be considered as alternatives
that may be
used alone or
in combination with other pest control practices.
INTEGRATED PEST MANAGEMENT:
WHAT IS IT?
The best way to control pests on
agricultural lands may be a
combination
of the chemical, biological, cultural, and mechanical
control
techniques described here. Using a
combination of these pest
control
practices has the following advantages:
- prevention of adverse impacts upon the
environment from
the continuous use of pesticides
- prevention of the development of
resistance to particular
pesticides in pest species
- provision of a backup pest control
system in the event that
any one method fails
<INTEGRATED
PEST MANAGEMENT>
03p101.gif (437x437)
Ideally integrated pest management
requires well-trained pest
managers who
understand the complex factors of ecosystem interrelations.
However, even
without such resource persons there are merits
to
introducing and experimenting with some alternative means of
control as
described in the previous sections, when the results of
pesticide use
are sickness and death to people.
Some of the most characteristic features
and goals of the integrated
pest
management Approach are:
* The focus is on the entire pest
population and their natural
enemies operating within an
ecosystem. The agroecosystem
is the management unit.
* The objective is to maintain pest levels
below a
pre-established economic threshold.
The goal is to manage
rather than eradicate the pest
population.
<ECONOMIC
THRESHOLD OF PEST MANAGEMENT>
03p102.gif (540x540)
* Control methods are chosen to supplement
the effects of
natural control agents (parasites,
predators, weather, etc.).
* Alleviation of the problem is long-term
and regional, rather
than localized and temporary, and the
harmful side effects
on the environment are minimized.
Thus, integrated pest
management should be part of government
policy.
* Monitoring is essential.
Pest population numbers need to be
regularly monitored, and also the
environmental factors
influencing pest abundance in order to
determine when to
apply control actions.
How monitoring is conducted depends
on the crop, the pest species, the
climate, the human skills,
and economic resources.
Simple monitoring procedures that
involve no special equipment or expenses
have been designed
for farmers with limited resources.
For example, with rice, a
system based on plant tapping can be
used to sample for the
green leafhopper.
Each week a farmer randomly picks 20
hills across the paddy.
He slaps the plants with force
several times with the palm of the
hand. He then counts
both adults and nymphs that fall on the
water. Finally, he
calculates the average green leafhopper
numbers per hill,
and based on this data makes decisions
whether or not the
pest needs to be controlled.
<MONITORING
BY PLANT TAPPING>
03p103.gif (540x540)
DEFINITION OF A PESTICIDE
"Pesticide is an umbrella term used
to describe any chemical
that controls
or kills a pest, be it insect, weed, disease, or animal.
Pesticides
are generally classed by the type of pest they control:
insecticide
(insects), herbicide (weeds), fungicide (fungus), rodenticide
(rodents),
nematicide (nematodes), acaricide (mites, ticks and spiders).
Pesticides
are also defined by their method of dispersal
(fumigant) or
mode of action, such as an ovicide, which kills the eggs
of
pests. Although they do not
specifically kill pests, insect growth
regulators
are considered pesticides because they modify the insect's
growth in
such a way as to halt its deleterious effects."
(Gips 8.8)
<FIGURE
5>
03p104.gif (600x600)
Pesticides used today belong to three
principal groups of
chemicals:
* Organochlorides are derivatives of
chlorobenzene that are
highly toxic and have long-lasting
effects. Included in this
type of chemicals are DDT, chlordane,
aldrin, dieldrin,
endrin, toxaphene, lindane, heptachlor,
among others.
* Organophosphates are highly toxic to men
and other
warm-blooded animals.
Examples are phosdrin, parathion,
methyl parathion, azodrin or nuvacron,
lorsban.
* Carbamates are derived from carbonic
acid. Like organophosphates,
they have inhibitive or disruptive
effects on the
central nervous system, which controls
all bodily functions,
they are very poisonous and take
immediate effect. Examples
are temik, furadan, lannate, sevin,
baygon. (Source:
Secretariat for Ecologically Sound
Philippines.)
EFFECTS OF PESTICIDE USE
The use of pesticides should be limited to
epidemic situations
in which all
other measures fail to provide control.
Pest management
programs
should seek to reduce both the frequency of application
and the
dosage. Following are some of the
common effects of
dependence on
pesticides.
Effects on
People
Pesticides can be inhaled by humans or
taken into the body
through the
skin. Body contact is a particular
problem during the
application
of pesticides. Failure to take safety
precautions and to
handle
certain pesticides carefully may even result in death.
Thousands
of
individuals suffer from pesticide poisoning every year.
Many die
annually. Fatalities have mainly
occurred among people
who handle
pesticides--farmers, crop dusters, farm workers, and
workers in
pesticide manufacturing factories. More
and more concern
is also
focussed on the issue of poisonings attributed to eating
food crops
and meat containing pesticide residues.
Effects on
Soil Fertility
Each square meter of fertile agricultural
soil contains millions
of life
forms--insects, earthworms, oligochaete worms, nematodes,
protozoa,
algae, fungi, bacteria, and yeast cells.
All these organisms
are
absolutely necessary for soil fertility maintenance.
The organisms
are involved
in: the conversion of bound nutrients
into
forms
available to plants; the break up of organic matter; the fixation
of nitrogen;
and the aeration of the soil. Their
presence ensures
that ecological
balance or equilibrium is maintained.
Continuous use
of pesticides
that do not decompose rapidly can alter this soil organism
community
and, ultimately, may reduce soil fertility.
Populations
of
earthworms, critical to some ecosystems, may be drastically
decreased by
chlordane, endrin, parathion, carbametes and most
nematicides.
Some fungicides and herbicides seem to
affect mostly
the
microflora, thus upsetting the dynamics of most nutrients in the
soil.
Effects of
Pesticides on the Balance of Nature
Most organisms in nature are regulated by
natural enemies
keeping them
in a state of balance with their environment.
Overuse
or misuse of
pesticides can interfere with this natural control system.
When this
happens, pest problems can actually be worsened.
During the last three decades, despite a
tenfold increase in
insecticide
use, crop losses to insect pests have nearly doubled.
Two
major factors
account for this near doubling of crop losses:
- more than 300 species of insects, mites
and ticks have developed
genetic resistance to pesticides
- pesticides have inadvertently destroyed
natural enemies of
certain insect pests, resulting in pest
resurgence and/or
secondary pest outbreaks
Some Other
Effects of Pesticides
Certain pesticides can also alter the
chemical makeup of
plants.
Some organochlorines can increase amounts of
particular
mineral
elements in corn and beans. Herbicides,
especially 2,4-D,
can induce
accumulation of nitrates in plants, with possible toxic
effects on
livestock and other animals. These
changes in plant
constituencies
can alter the physiology of certain crop plants, such as
corn, making
them more susceptible to insect or pathogen attack.
In
particular,
2,4-D can render some crops more susceptible to pests
and disease.
Effects on
the Aquatic Environment
Pesticides transported from treated fields
into the aquatic
environment
by runoff and erosion are distributed throughout water,
mud, and the
organisms living in both. The buildup
of pesticides in
a given body
of water depends on:
- how much pesticide is entering the
aquatic system
- the persistence of the pesticide
- the tendency of the pesticide to
bioaccumulate, or build up
within an organism and food chains
- the sites or organisms in which the
pesticide concentration is
being measured
Pesticide
Persistence
Pesticide persistence is the length of
time a pesticide remains
biologically
active, or toxic, to target pests. Most
pesticides are rated
according to
their persistence, as indicated in the table below.
PERSISTENCE OF CHEMICALS
Duration of
Chemical
Examples
Activity
Group
Non
Persistent 1-12 weeks
Organo-phos-
Malathion,
phorous com- methyl para-
pounds; thion, para-
Carbamates thion carbaryl
Moderately
1-18 months
--
2,4-D, atra-
Persistent
zine
Persistent
2-5 years
Organochlor-
DDT, BHC,
ine(1) comp-
lindane, al-
ounds drin,
dieldrin,
endrin,
chlor-
dane,
hepta-
chlor,
cam-
pheclor
Permanent
Degraded to
Compounds
Phenyl mer-
(residues)
(permanent res-
containing
cury acetate,
idue
mercury,
arsenate of
arsenic or lead lead
(1) A number
of organochlorine compounds are in the "non-persistent"
or
"moderately persistent" classifications, e.g., methoxychlor, dicofol,
chlorobenzilate.
In general, persistent pesticides (those
which remain biologically
active for
longer periods) are less soluble and volatile but have a
strong
tendency to become adsorbed (attached to particles of soil).
The best
known of the persistent pesticides are the organochlorine
insecticides
(DDT, Aldrin, Endrin, Heptachlor, etc.), the herbicide
simazine, and
the fungicide benomyl. These can remain
up to 14-17
years in the
soil. The longer the pesticide
persists, the greater the
likelihood
that it will move from the target area via soil, water, air,
or organisms,
and influence adjoining ecosystems.
HOW PESTICIDES MOVE ABOUT THE ENVIRONMENT
Pesticide
Pathways
Pesticides are applied in either liquid or
powder form. Both
forms can be
sprayed on the soil or plants. During
application, some
of the
pesticide is lost to the air through drifting or volatilization.
After
application, the pesticides can travel in various ways in the
environment:
- biological degradation by soil
microorganisms, chemical
degradation on the soil surface, or
foliage photo-decomposition
as a result of sunlight
- volatilization
- absorption by plants (which may be eaten
by animals and/or
humans)
- adsorption onto soil particles
(especially clay and organic
matter) that may move with erosion
- dissolution in water (rain or
irrigation) that becomes surface
runoff or that infiltrates into the soil,
later appearing in
surface water or groundwater supplies.
Pesticides take one pathway rather than
another depending on
a number of
factors. Principal among these
are: characteristics of
the pesticide
itself; the soil type; the strength and amount of rainfall;
the type of
erosion control measures being used; and the temperature.
In general,
pesticide compounds that are more water-soluble
and less
persistent will move primarily in runoff water.
Those that
are more
firmly adhered or adsorbed to soil particles will generally
move with
sediment.
Distribution
in Soil
Organic content and texture are the most
important soil
characteristics
influencing how pesticides move in the soil.
Other
soil
properties--pH, moisture content, temperature, mineral content--may
also
influence pesticide persistence and movement.
For
example, the
greatest persistence of organochlorines is found in soils
rich in
organic matter, with high clay content and with acid pH.
Water and
pesticides compete for adsorption sites on soil particles;
therefore, as
moisture in the soil decreases, the amount of pesticide
adsorbed may
increase. Some pesticides in the soil
are subject to
leaching.
Leaching of pesticides is influenced by the
amount and
rate of water
flow, and the formulation, concentration, and rate of
degradation
of the pesticide. Pesticides may move
laterally through
soil as well,
appearing in surface or sub-surface runoff.
Cultivation
of the soil
can also enhance loss of volatile pesticides.
Distribution
in Water
Pesticides enter lakes, ponds, rivers, and
other waterways from
runoff of
treated areas, from drift, or from direct pesticide (mainly
herbicide)
applications. The quantity of a
pesticide that moves into a
water course
from treated areas depends upon topography, intensity
and duration
of rainfall, soil erodability, and land management
practices.
Improved erosion control practices can be
very important
for keeping
pesticides from entering the larger environment.
Sound
project planning
requires consideration of the methods for erosion
control in
light of their applicability for pesticide control.
If pesticides enter a body of water in a
dissolved state, the
pesticide in
solution will move as the water moves.
The pesticide
may:
remain in solution in the water; precipitate
out of the water
and end up in
bottom silt; be taken up by aquatic organisms; be
biologically
or chemically degraded; or more commonly become
adsorbed onto
live or dead particulate matter which eventually
settles to
the bottom as sediment. Pesticides
adsorbed on sediment
will disperse
with the sediment. The finest particles
(those carrying
the greatest
concentration of pesticide) will be transported the
farthest and
will typically be the last to settle out of the water to
the bottom in
lakes or quiet water. Systems with
running water
which flushes
away pesticide pollutants tend to be more resilient
than those
where water is static.
<FIGURE
6>
03p110.gif (486x486)
Until they chemically degrade, pesticides
will not disappear.
Because the
system is dynamic, even those deposited in bottom muds
may be later
churned up and carried downstream.
Also, pesticides
continually
separate from muds and remain in the water.
Once in
the water,
the pesticides may reach the surface and volatilize
(become
gaseous) or be degraded by sunlight. On
the bottom of a
water body,
there is often a lot of microbial activity in the organic
matter.
At the bottom, biological decomposition
consumes oxygen,
thereby
creating anaerobic (without oxygen) conditions that favor the
degradation
of many pesticides.
If pesticides must be used, try to use
those that will degrade
rapidly in
water in order to protect nearby aquatic environments.
Also, keep in
mind that the products of pesticide degradation may be
toxic.
Information appropriate for your region is
available by writing
to the
Pesticides Action Network (PAN).
Addresses of the regional
offices of
PAN are in Appendix B.
SOME FACTORS THAT SHOULD BE CONSIDERED
BEFORE APPLYING PESTICIDES
Local
Experience
Check with local farmers or extension
agency personnel to see
what local
experience has been with given pesticides.
There is no
prescription
for the persistence and potency of pesticides.
It can
vary
depending upon local conditions.
Alternative
Pest Control Measures
Check the variety of alternative
non-chemical control measures
that may meet
project needs. Become familiar with
possible negative
effects of
the pesticides you may be considering.
Some of these
alternatives
are described elsewhere in this chapter.
Synergism
Consider the possibility of relationships
between two or more
pesticides
used in the same area before applying more than one to a
field.
When two or more pesticides are applied at
the same time,
their
combined toxicity may actually be greater than the sum of their
individual
toxicities. This is called synergism.
Timing of
Application
If possible, apply pesticides well before
heavy rains if they are
to do the
most good in controlling target organisms.
The rate at
which
pesticides are washed off the land is usually high at first.
This rate of
loss, however, decreases reaching a steady rate, unless
changed by
weather, soil, temperature, soil moisture level, acidity, or
cultural
practices. Some pesticides have greater
losses if they are
applied to
wet soil rather than dry, especially if runoff occurs soon
after
application. When pesticides are
incorporated into the soil, the
loss to
runoff is not as great as when they are just left on the soil
surface.
Pesticide
Movement
Explore the ways in which pesticides might
move through the
environment
to help design projects that will contribute less to
pollution.
Runoff travelling from cropland to open
water can carry
pesticides.
As the water crosses other lands, some
pesticide is left
behind.
While the total amount entering the water is
decreased,
nearby land
may also be contaminated by pesticides.
This pollution
can have
damaging impacts on animals and humans.
Precautions
Necessary
If
you are going to introduce pesticides it is important to
provide
training to those who will be applying them.
Include precautions
regarding
bodily exposure of those applying chemicals and
exposure of
others in the area. At the very least,
read the directions
on the label
carefully. These will instruct on the
way in which the
chemical can
be safely applied, the time that needs to elapse following
application
before the area is safe, and the relation of using the
chemical to
the maturing of the crop. Also, read
the precautions on
the label and
understand the steps to take in case of emergencies
such as
swallowing some, or coming in physical contact with the
chemical.
Never reuse pesticide or herbicide
containers.
CHECKLIST FOR PROJECTING THE IMPACTS OF
CHEMICAL PESTICIDE USE AND THE
POTENTIAL FOR ALTERNATIVES
Addressing questions such as the following
will provide the
project
planner with a background for making informed judgments
concerning
environmentally sound pest control.
* Are chemical pesticides suggested for
the project?
* Have all pest management options been
considered?
* Are alternative pesticides available
that are relatively safer
to use?
* Are there plants with pesticidal
properties which could be
used?
Are they locally available?
* Are the pesticides to be used in the
project recommended for
use on these particular crops by the
manufacturers? By the
government?
* Are similar pesticides being used
locally for health purposes,
such as malaria control?
* Can a species-specific pesticide be
used?
* Does the project design recognize the
possibility that target
species will develop resistance to the
pesticide and larger
quantities may be required each year to
control the pest?
* Is it possible to change pesticides to
reduce the likelihood of
target species developing resistance to
an important pesticide?
If so, can a schedule for implementation
be developed?
* Is the pesticide persistent in
soil? Will it tend to accumulate
in the soil?
* Might the pesticide suggested for use
kill beneficial soil
micro-organisms?
* Does the pesticide tend to bioaccumulate
(biologically increase)
or biomagnify (biologically grow) in
organisms? If
so, which organisms would it affect in
the immediate area, if
any?
* Is there a body of water nearby?
If so, are people downstream
highly dependent upon aquatic resources
such as
fisheries, aquaculture, and drinking
water which might be
contaminated by an accidental discharge
of pesticides because
of the project?
What effect would contamination of the
water have on health, finances, and other?
* Is it likely that erosion will carry
pesticides into downstream
water bodies?
If so, could such pesticides affect fisheries,
aquaculture projects, and domestic water
use?
* Have adequate precautions been taken to
protect workers
from pesticide poisoning during
transport, storage, and
application of pesticides?
Are instructions available in local
languages with culturally sensitive
symbols?
* Can pesticide applications be timed to
avoid rapid loss to
wind and rain?
* Is it possible to develop plans that can
be put into effect
easily and simply in case of an
emergency, such as accidental
pesticide pollution or physical contact?
* What alternative project designs could
be used at the site to
minimize environmental impacts from
pesticide use?
CHAPTER 9
AGROFORESTRY SYSTEMS
Agroforestry systems are production
strategies designed to
promote a
more varied diet, new sources of income, stability of
production,
minimization of risk, reduction of the incidence of insects
and disease,
efficient use of labor, intensification of production with
limited
resources, and maximum returns with low levels of technology.
Some form of
agroforestry has been practiced by many traditional
agriculturalists.
For a number of reasons such as commercial
plantation
development, cattle raising, deforestation, and population
pressures,
these practices may have been abandoned.
Recognizing
the value of
combining trees with crops and livestock as a means of
conserving
soil, increasing the multiple uses of land, rehabilitating
degraded
sites, and diversifying to reduce risk is leading development
workers to
consider introducing or reintroducing agroforestry practices
with
improvements based on research and experience.
This recognition has grown out of a
combination of acknowledging
traditional
experience and scientific research.
Traditional bush
fallow and
shifting cultivation could be said to be a precursor of the
modern
understanding of agroforestry. The
clearing of woody vegetation
for crops for
a period of years and reestablishment of forest in
the fallow
period was a combination of agriculture and forest in
sequence that
has been practiced in many regions.
Taungya is an
early form of
agroforestry that introduced tree seedlings planted by
foresters
combined with growing of crops in the cleared area until
the tree
canopy provided too much shade.
Traditional kitchen
gardens have
typically been a mixture of shrubs, food crops, and
medicinal
plants in a multistoried arrangement.
For some species of
coffee and
cacao interplanting with shade trees has been a necessity.
Some more
purposeful combinations of trees and crops practiced
today are
introduction of fodder trees in fields; dispersing indigenous
species in
fields for nutrients and fodder, as for example Acacia
albida in
millet fields; use of trees for shelter belts and hedgerows.
Alley
cropping is a recently introduced system that involves planting
and intensive
management of relatively close-spaced rows of nitrogen-fixing
trees and
shrubs such as Leucaena and Gliricidia, with a crop
such as maize
in between. (Winterbottom 9.19)
DEFINITION AND CLASSIFICATION
Agroforestry denotes a "sustainable
land and crop management
system that
strives to increase yields on a continuing basis, by
combining the
production of woody forest crops (including fruit and
other tree
crops) with arable or field crops and/or animals simultaneously
or
sequentially on the same unit of land, and applying management
practices
that are compatible with the cultural practices of the
local
population." (International Council for Research in Agroforestry,
1982)
There are several ways to classify and
group agroforestry
systems (and
practices). The most commonly used
are: structure
(composition
and arrangement of components); function (the use of
trees);
ecologic (ecosystem or climatic zone); and socio-economic scale
and level of
management.
Structure
Agroforestry systems can be grouped as:
- agri-silviculture:
the use of land deliberately for the
concurrent
or sequential production of agricultural
crops field and
tree crops) and forest crops (woody
forest plants)
- silvo-pastoral systems:
land management systems in which
forests are managed for the production
of wood, food and
fodder, as well as for the rearing of
domesticated animals
- agro-silvo-pastoral systems:
systems in which land is managed
for the concurrent production of
agricultural (field and
tree crops) and forest crops (woody
forest plants)and for the
rearing of domesticated animals
- multipurpose forest tree production
systems: in which forest
tree species are regenerated and managed
for the ability to
produce not only wood, but leaves and/or
fruit that are
suitable for food and/or fodder
Function
The functional basis for classifying
agroforestry systems refers
to the main
output and role of various trees, especially the woody
ones.
These would be productive functions
(production of "basic
needs"
such as food, fodder, fuelwood, and other products), or protective
roles (soil
conservation, soil fertility improvement, protection
offered by
windbreaks and shelterbelts, and so on).
The functional
basis is
discussed in detail later in this chapter.
Ecologic or
Climatic
On an ecological basis, systems can be
grouped for any defined
agro-ecological
or climatic zone such as lowland humid tropics, arid
and semi-arid
tropics, tropical highlands. They can
also be based on
climatic
zones defined by rainfall patterns or other groupings that
serve the
purpose.
Socio-Economic
Scale and Level of Management
The socio-economic scale of production and
level of management
of the system
can be used as the criteria to designate systems as
commercial,
intermediate, or subsistence.
Each of these ways of looking at
agroforestry systems is useful
and
applicable in specific situations, but for each there are limitations
so that no
single way of grouping is universally applicable.
Classification
depends upon the purpose for which it is intended.
SOME ADVANTAGES OF AGROFORESTRY SYSTEMS
By combining agriculture and forestry/tree
crop production, the
various
functions and objectives of forests and food crops production
can be better
achieved. There are advantages of such
integrated
systems over
agriculture and/or forestry monocultures.
(Wiersum
9.18)
Ecological
Advantages
* A more efficient use is made of the
natural resources. The
several vegetation layers provide for an
efficient utilization of
solar radiation, different kinds of
rooting systems at various
depths make good use of the soil and
short-lived agricultural
plants can profit from the enriched
topsoil as a result of the
mineral cycling through treetops.
By a three dimensional
use of space, total growing capacity is
increased. By including
animals in the system, unused primary
production can
also be utilized for secondary
production and nutrient recycling.
* The protective function of the trees in
relation to soil, hydrology,
and plant protection can be utilized to
decrease the
hazards of environmental degradation.
It should be
kept in mind, however, that in many agroforestry
systems the
components may be competitive for light, moisture, and
nutrients;
trade-offs must be considered. Good
management can
minimize this
interference and enhance the complementary interactions.
Economic and
Socio-Economic Advantages
* By ecological efficiency the total
production per unit of land
can be increased.
Although the production of any single
product might be less than in monocultures,
in some instances
production of the base crop may
increase. For
example, in Java it has been
demonstrated that after introduction
of the tumpang-sari or taungya system,
dryland rice
production increased significantly.
* The various components or products of
the system might be
used as inputs for production of others
(for example, wooden
implement, green manure) and thus the
amount of commercial
inputs and investments can be decreased.
* In relation to pure forestry
plantations, the inclusion of
agricultural crops with trees, coupled
with well-adjusted
intensive agricultural practices, often
results in increased
tree production and less costs for tree
management (e.g.,
fertilization and weeding of agricultural crops may also
benefit tree growth), and provide a
wider array of products.
* Tree products can often be obtained
throughout the year
providing year-round labor opportunities
and regular income.
* Some tree products can be obtained in
the agricultural
off-season (e.g., dry season), when no
opportunities for other
kinds of plant production are present.
* Some tree products can be obtained
without much active
management, giving them a reserve
function for periods of
failing agricultural crops, or special
social necessities (e.g.,
building a house).
* By the production of various products a
spreading of risk is
obtained, as the various products will
be affected differently
by unfavorable conditions.
* Production can be directed towards
self-sufficiency and
marketing.
The dependency on the local market situation
can be adjusted according to the
farmer's need. If so desired,
the various products are entirely or
partially consumed,
or delivered to the market, when
conditions are right.
SOME CONSTRAINTS OF AGROFORESTRY SYSTEMS
There are a number of limiting conditions
or constraints to
implementing
agroforestry systems. These constraints
should be
recognized
and efforts made to overcome them, if agroforestry is to
be applied
successfully.
* A major ecological constraint is that
agroforestry systems are
ecosystem-specific and on certain low
grade soils the choice
of suitable plant species might be
limiting, although many
trees are better adapted to poor soils
than annual crops.
* The competition between trees and food
crops, and the
priority that must be given to them to
meet basic needs,
may exclude poor farmers, who have very
little land, from
tree growing.
* In promoting tree planting, short term
benefits as well as
long term benefits are needed.
Economic or production
incentives need to be included.
* A common economic constraint is that
some newly
established agroforestry systems might
need substantial
investment costs to get started (e.g.,
planting material, soil
conservation, fertilizer).
For these investments, credit may
be needed.
In most agroforestry systems one may need a
few years before the first yields are
obtained. In some cases,
financial support is needed to provide
for this waiting period.
* Size of plot may affect the kind of
inputs. In areas with a
high population pressure and poor soils,
the private landholdings
might be too small as viable production
units. In
this case some kind of cooperative
effort might be necessary.
* Availability of seeds and/or seedlings
is a critical variable for
agroforestry projects.
Check with government offices, university
forestry or botanical departments, or
nongovernmental
organizations involved in species
research for the best species
to meet your needs.
Then check on availability of seeds
and/or seedlings.
In most cases, longer run planning includes
developing small nurseries along with
planting and
maintaining trees.
* Management of livestock sometimes can
conflict with agroforestry
ventures especially in areas where
cattle or goat
herding is being practiced.
* Wildlife is a problem in some
areas. Where elephant herds
still exist they have threatened
forestation projects.
* Pests may also threaten agroforestry
projects--both tree and
ground crops.
Current infestation of locusts in some areas of
the Sahel in Africa are a problem.
* In areas with complex clan or communal
land systems,
developing agroforestry systems may be
difficult. Tenure
rights are a fundamental consideration
in agroforestry. They
may be a limiting factor.
* Tree tenure is also a possible
constraint. In many cases,
land on which trees may be planted and
protected is not
owned by those who planted them.
The planters, then, may
not be legally entitled to harvest the
trees or the produce of
the trees.
Further, in some countries there are laws that
restrict the harvesting/cutting of trees
for any purpose
regardless of who owns the land on which
they are planted.
It is therefore necessary to check
before undertaking a tree
planting project to see:
- who owns the land
- what are the regulations about protecting
the seedlings
- what are regulations about harvesting
the trees and/or
produce of the trees
* Factors that may limit the participation
of people and affect
their motivation need to be
considered. In addition to land
and tree tenure these include other socio-political policies of
the government as well as some
traditional social mores.
* In all cases, it is essential that the
local population is
directly involved and traditional
farming knowledge taken
into account in the planning and design
of the system. (See
Chapter 3) Agroforestry is a complex
form of land-use and
requires adequate farming
knowledge. Local knowledge and
experience is still available about
traditional agroforestry
systems.
For developing new agroforestry techniques,
knowledge
of
traditional land use and farming systems and
additional
education and/or extension work is essential.
<WOMEN
GROWING SEEDLINGS>
03p121.gif (540x540)
ROLE OF WOMEN IN AGROFORESTRY
Women have traditionally been involved in both agriculture
and in the
use and management of trees. Most often
women harvest
the products
of trees. Yet women have often been
ignored in the
design of
agroforestry projects. There are
significant examples of
women taking
the initiative to create possibilities for tree planting
and relating
trees to the farm system. Notable among
these are the
Green Belt
Movement of the National Council of Women, Kenya, The
Forestation
and Ecological Education Project of Mujeres en Desarrollo
(MUDE) in the
Dominican Republic, and the Chipko movement in
India.
Projects that involve participation of women
from the outset
have been
more sustainable. (Fortmann and
Rocheleau 9.2)
<TREES
HAVE MANY USES>
03p122.gif (486x486)
THE ROLE AND EFFECT OF TREES
Agroforestry systems are multiple use
systems in which the
tree
components provide most of the multiple benefits.
The management
of the tree
component can affect, directly or indirectly, the
other
ecosystem components, for example soil conservation, nutrient
recycling,
the hydrological cycle, as well as bio-components (other
crops, weeds,
insect populations, micro-organisms).
Thus, through
management of
trees these other components can to some extent be
controlled.
Perhaps the most important ecological role
of trees in farmlands
is their
effect on soil conservation.
Effect on
Soil Conservation
Inclusion of trees usually increases
organic matter content, and
improves
physical conditions of the soil.
(Wiersum 9.18)
<LINKAGE
INTERACTION>
03p123.gif (540x540)
Effect on
Nutrient Recycling
Below is a schematic presentation of
nutrient relations and
advantages of
ideal agroforestry systems in comparison with common
agricultural
and forestry systems.
<COMPARISON
OF SYSTEMS>
03p124.gif (600x600)
Effect on
Hydrological Cycle and Erosion
Trees also influence hydrological
characteristics from the micro-climate
level up to
the farm and local levels.
<EFFECT ON
HYDROLOGICAL CYCLE AND EROSION>
03p125.gif (540x540)
A summary of linkages between
agroforestry, land management,
and soil
conservation is found in the table on the following
page.
EXAMPLES OF TRADITIONAL AGROFORESTRY SYSTEMS
Traditional agroforestry represents
centuries of accumulated
experience of
interaction with the environment by farmers without
access to
scientific information, external inputs, capital, credit, and
developed
markets. Shifting cultivation (swidden
agriculture and the
slash and
burn system) was among the earliest forms of agroforestry
systems.
These methods were sustainable under
conditions of low
population
pressures and long fallow periods.
LINKAGES BETWEEN AGROFORESTRY, LAND
MANAGEMENT, AND SOIL CONSERVATION
Factors
AGROFORESTRY
FARM/RANGE
MANAGEMENT
SOIL CONSERVATION
Affecting
Sustainablity
and
FARM
RANGE
Productivity
Soil
Moisture - Alley cropping, line
plantations - Use of compost,
cover- - Controlled grazing
- Incorporating organic matter into
Retention
and dispersed trees to
provide: crops
the soil
* Organic matter
- Crop-residue left in
fields - Rotational grazing
- Preparing micro-catchments,
contour ridges or other micro-site
* Shade to reduce
surface - Mulch
- Fire Management
improvements.
temperature
Soil
Fertility - Nutrient cycling and
Nitrogen - Crop rotation
(including - Use of Animal
- Contour vegetation strips
fixation
legumes)
Manure
Water
Erosion - Surface Runoff
reduction - Contour
farming - Range
rotation - Berms, ditches,
ridges
Control
through:
* Establishment of
trees/ - Maintaining soil
tilth - "Grazing
reserves" - Benches or
terraces
shrubs along
physical
- Waterway and gully control
conservation
features - Maintaining
maximum - Contract
grazing - Protection of stream
banks
plant cover
linked to vegetation
* Trees along
canals and
rehabilitation or
waterways
protection.
Wind
Erosion - Wind reduction
through: - Maintaining
maximum - Controlled lopping
- Windbreaks
Control
plant
cover for fodder
* Dispersed
Trees - Natural
vegetation strips
- Palisades, other physical
left when clearing new land
treatment in extreme cases
* Borderline
Trees - Minimum till
cultivation
- Dune
stabilization
Access
- Live fencing
- Stock driveways
left - Herding as opposed
- Layout of soil conservation
Control
when laying out
fields. to letting animals
plantings to reinforce
roam freely
fencelines and livestock trails.
- Alignment of livestock trails
- Borderline Trees
- Tethering or
corraling livestock
Source:
Weber and Stoney 3.8
Throughout the tropics, traditional
agroforestry systems may
contain well
over 100 plant species per field. These
are used for
construction
materials, firewood, tools, medicine, livestock feed, and
human
food. In Mexico, for example, Huastec
Indians manage a
number of
agricultural and fallow fields, complex home gardens, and
forest plots
totalling about 300 species. Small
areas around the
houses
commonly average 80-125 useful plant species, mostly native
medicinal
plants. Management of the noncrop
vegetation by the
Huastecs in
these complex farm systems has influenced the evolution
of individual
plants and the distribution and composition of the total
crop and
noncrop communities. Similarly, the
traditional pekarangan
system in
West Java commonly contains about 100 or more plant
species.
Of these plants, about 42% provide building
materials and
fuelwood, 18%
are fruit trees, 14% are vegetables, and the remainder
constitute
ornamentals, medicinal plants, spices, and cash crops.
Javanese agroforestry systems usually
consist of three
stages--kebun,
kebun-campuran and talun--each stage serving a
different
function (Christanty 9.1). The first
state, kebun, is usually
planted with
a mixture of annual crops. This stage
has a high
economic
value since most of the crops are sold for cash.
After two
years, tree
seedlings have begun to grow into the field and there is
less space
for annual crops. The kebun gradually
evolves into a
kebun-campuran,
where annuals are mixed with half-grown perennials.
The economic
value of this stage is not as high, but it has a
high
biophysical value, as it promotes soil and water conservation.
After
harvesting the annuals, the field is usually abandoned for two
to three
years to become dominated by perennials.
This stage is
known as
talun, the climax stage in the talun-kebun system.
The
talun has
both economic and biophysical values.
To begin the process after clearing the
forest, the land can be
planted to
dryland rice (huma) or wet rice paddy (sawah), depending
on whether
irrigation water is available.
Alternatively, the land can
be planted
with a mixture of annual crops, the first stage (kebun).
In some areas
the first agroforestry stage (kebun) is developed after
harvesting
the dryland rice (huma) by following the dryland rice with
annual field
crops. If the kebun is mixed with tree
crops or bamboo,
it becomes
second stage (kebun campuran), a mixed garden.
After
several years
perennials will dominate and create the third stage, a
perennial
crop garden (talun). (See figure on
page 17.)
Agroforestry systems are also widespread
among many tribal
groups, for
example, in the Amazon region, the Himalayas, the
Philippines,
and the Sub-Saharan countries of Africa.
Unlike other
shifting
cultivators, the Bora in Brazil do not have a transition
between
cropping and fallow, but rather a continuum from a cropping
system
dominated by crops to an old fallow composed entirely of
natural
vegetation. This process may take as
long as 35 years or
more.
Given current population pressure trends and
deforestation
rates in the
area, this system may not be sustainable in the future.
DESIGN OF AGROFORESTRY COMBINATIONS
Arrangement of component plant species in
space and time is
also an
important but difficult factor in agroforestry because of the
many
variations in the types of agroforestry practices and the conditions
under which
they are practiced. When attempting to
improve
such systems
or to devise new ones, it is therefore necessary to know
about both
the short-term productivity of the plants and the
long-term
sustainability of the system. Thus,
depending on whether
the tree/crop
interaction is favorable or not, plant arrangements have
to be devised
to maximize the beneficial interactions and minimize
the
undesirable ones. There are also
several other factors to be
taken into
account, such as:
- growth habits and growth requirements of
the component
species when grown near other species
- simplicity of management procedures for
the whole system
- realization of additional benefits such
as soil conservation
Species and
plant arrangement patterns in agroforestry are very
situation
specific.
One way to develop agroforestry is to
imitate the structure and
function of
natural communities. In the humid
tropics successional
ecosystems
can be particularly appropriate models for the design of
agricultural
ecosystems. In Costa Rica, plant
ecologists conducted
spatial and temporal
replacements of wild species by botanically
and/or
structurally/ecologically similar plants.
Thus, successional
members of
the natural system such as Heliconia species, cucurbitaceous
vines,
Ipomoea species, legume vines, shrubs, grasses, and
small trees
were simulated by plantain, squash varieties, yams,
sweet
potatoes, local bean crops, Cajanus cajan, corn/sorghum/rice,
papaya,
cashew, and Cassava species, respectively.
By years two
and three,
fast-growing tree crops (for example, Brazil nuts, peach,
palm,
rosewood) may form an additional stratum, thus maintaining a
continual
crop cover, avoiding site degradation and nutrient leaching
and providing
crop yields throughout the year.
Some agroforestry systems are given below
based on materials
published by
the International Council on Agroforestry (ICRAF),
Kenya.
(Spicer 9.12) Information about the choice
of species and
their
planting and management schedule needs to be sought locally
or
regionally. Some of the techniques
discussed below are described
on pages
53-58.
1. Alley
Cropping in High Potential Areas
Alley cropping is appropriate for home
gardens and for cultivated
arable
land. This system can be helpful in the
following
ways:
- providing green manure or mulch for
companion food crops;
in this way plant nutrients are recycled
from deeper soil
layers
- providing prunings, applied as mulch,
and shade during the
fallow
- suppressing weeds
- providing favorable conditions for soil
macro- and micro-organisms;
when planted along the contours of
sloping land,
to provide a barrier to control soil
erosion
- providing prunings for browse, staking
material and firewood
- providing biologically fixed nitrogen to
the companion crop
Trees and shrubs suitable for alley cropping should meet most
of the
following criteria:
- can be established easily
- grow rapidly
- have a deep root system
- produce heavy foliage
- regenerate readily after pruning
- have good coppicing ability
- are easy to eradicate
- provide useful by-products
Multipurpose
species are generally preferable because they give the
alley
cropping system flexibility. Leguminous
trees and shrubs,
because of
their ability to fix atmospheric nitrogen, are preferred
over
non-leguminous species.
2.
Contour Planting
Contour planting is useful where there are
the following
conditions:
- poor or easily depleted soils
- sloping (erodible) land as well as
non-erodible land
- medium to high population density
Contour
planting can help in the following ways:
- to restore/improve soil nutrient and
increase organic material
content
- to reduce soil and water run-off
- to spread the risk of crop failure during
extremely dry
seasons by moderating the effects of
excessive moisture
evaporation on exposed land
- to add wood products for home
consumption or sale
The appropriate farming systems in which
to utilize this
system are
permanent crop cultivation, medium to small farm size,
and medium to
high labor input available per unit of land.
Fast
growing
species can be established at the start of the growing season
which gives
them the opportunity to establish while livestock are
kept out of
the arable areas.
3.
Fodder Bank - Cut and Carry
Establishment of fodder banks is useful
where there is high
population
density and nearby markets for livestock products.
Fodder banks
can improve fodder availability and quality, particularly
during the
late dry and early wet season. They
also seem to
restore/improve
soil nutrients and organic matter content.
Creating these banks of trees will
facilitate ease of fencing.
Pure stands
(blocks, strips, lines) of trees (mainly leafy fodder) can
be planted
near cattle kraals, in homestead gardens, in arable lands
and grazing
areas, along watercourses and around the margins of
watering
places.
The appropriate farming system for fodder
banks is on the
small farm
where there is intensive land use, a kraal feeding system
and high
labor input per animal.
4.
Fodder Bank - Grazing
Fodder banks for grazing are usually
located in grazing
areas.
They may be on hills (especially pod
species), on uplands,
along
watercourses, and on borders of watering places.
Fodder banks for grazing will improve
fodder availability and
quality in
low to medium population density areas, and restore/improve
soil
nutrients and level of organic materials.
A mixture of trees (pods and leaves) and
grasses (fenced) can
be planted in
blocks. Pod and foliar species should
be planted in
hedges.
Scattered trees need to be protected by
thorns. The pod
species will
provide a feed supplement for cattle during the early
rains.
Species selected must be adaptable to
local climate and soil as
well as
having other attributes such as palatability, high protein
content, ease
of establishment by direct seeding, transplanting or
truncheon
setting. Pod trees for hills and
uplands seed from August
to
December. Self-seeding varieties in
watering places must be
tolerant of
up to 6 months waterlogging. They
should have a limited
water uptake
rate in order not to have a detrimental effect on the
hydrology of
the area. Foliar species should be
maintained at the
lower levels.
5.
Fruit Improvement
In the homestead arable area and garden it
is useful to
add
fruit-producing trees. Scattered trees,
planted near the home
will allow
for protection from animals. Fruit
trees may also be
planted to
create boundaries around the homestead.
This will
improve
nutrition, produce fruit for sale, provide shade, and firewood.
Use of the system is limited by the
availability of improved
fruit
varieties. There needs to be adequate
extension support to help
with choice
of varieties and management, e.g., propagation, grafting
and budding,
planting, mulching, watering, and control of weeds,
pests, and
diseases.
6.
Hedges/Living Fences
Hedges and living fences are useful in
areas with medium to
high
population density and where animals roam freely in the area.
Live fences
or hedges provide an alternative to constructed fencing
for:
* The demarcation of boundaries; for
example between/around
schools, farms and fields (particularly
paddocks in grazing
schemes).
* Protection from the ravages of
free-grazing livestock; for example
crop lands, orchards, nurseries,
woodlots, dams,
protein banks (grazing schemes),
vegetable gardens and
homes.
In addition
hedges can offer secondary benefits, such as reducing the
adverse
influence of wind, and they provide not only organic material
to adjacent
soils but also multiple tree products (firewood, poles,
fruit, fibre,
medicines, etc.) to the local community.
The appropriate farming system for living
fences is the small
to medium
sized farm with permanent crop cultivation.
7.
Mixed Intercropping
Mixed intercropping is most useful in poor
or easily depleted
soils, on
flat to gently sloping land, in areas of medium population
density.
This system will serve to restore/improve
soil nutrients and
increase
organic materials.
The appropriate farming system is that
with permanent crop
cultivation,
medium to small farm size using medium labor input per
unit of land
and no animal cultivation (at high tree densities).
8.
Multistorey Planting of Domestic/Industrial
Tree Crops
Multistorey tree crops are best suited to
home gardens and as
the upper
storey of productive trees in hedges or plantations.
Multistorey
planting fits well in areas with high population density
and high
rainfall. It will contribute resources
for tree products, some
of which will
supply household requirements. This may
also reduce
cash
expenditures, and add to cash income.
Multistorey tree crop
systems are
appropriate for small sized farm systems with high labor
input per
unit of area.
9.
Tree Planting Around Watering Places and
Dams
Tree planting around watering places and
dams is appropriate
where there
is a high population density or presence of animals in
the area.
Planting trees will reduce the damage to the
watering
place and
dams that is caused by livestock. It
will also provide
materials for
wood products for home consumption or sale.
Trees
can be laid
out in strips or planted in woodlots. A
mixture of trees
and grasses
is helpful. Planting can also be spaced
and mixed with
multistory
species. The appropriate farm system is
a small to
medium sized
farm with permanent crop cultivation.
10.
Selective Clearing
Selective clearing is useful in areas with
substantial acreage of
native
woodlands. It is particularly useful in
resettlement areas
where there
is a low population density. Selective
clearing will
conserve
functional indigenous vegetation, biodiversity, and help to
ensure future
supplies of woodland products and germ plasm.
In
this system
selected trees are left in croplands.
Strips of trees and
shrubs are
left around newly opened plots, between fields and along
roads, tracks
and watercourses. The appropriate farm
system is the
medium to large
farm with low labor input per unit area.
11.
Woodlot Planting for Fuelwood and Poles
Woodlot planting for fuelwood and poles is
appropriate for
deforested
areas, and for all areas with a market for poles and/or
firewood.
Such woodlots can produce fuelwood/poles to
meet household
and/or
household industries requirements. They
may also add
to the cash
flow of the family. Woodlots should be
fenced. Where
possible
"live fences" should be established within the protection
offered by
the fence. Firebreaks are
recommended. The appropriate
farm system
is the medium to large farm with low to medium labor
input per
unit area. The system is also
appropriate for tobacco
farms (for
barn construction as well as curing) and small industries
e.g., brick
works or small mines.
More detail about these systems is
available from the International
Council for
Research in Agroforestry, Nairobi, Kenya.
(See
Appendix B
for address.)
PART IV:
CONCLUSION
CHAPTER 10
CONCLUSION:
A CHECKLIST FOR SUSTAINABLE
DEVELOPMENT, EXAMPLES OF
TRADITIONAL
SYSTEMS, AND LONG TERM
EVALUATION
This manual has reviewed the relation
between the environment
and
agricultural projects. With a framework
for planning, the
background
technical information and other considerations have been
provided.
This is only a start.
Now you have to adapt the information
here to the
local situation and seek the specific technical assistance
and
information identified with the help of this manual.
The technical guidelines and information
are designed to give
the
development worker a better understanding and to indicate the
possible
effects. In most cases the decisions to
be made involve
trade-offs.
For example, should the community introduce
high priced
inorganic
fertilizer that will produce quick results but is expensive
and does not
improve the quality of the soil; or alternatively, should
they try to
introduce techniques for organic fertilizing that will
improve the
soil but incur increased labor costs and sometimes
sacrifice
alternative uses of the local materials?
The ideals sometimes advocated here also
may not be possible.
Decisions
about trade-offs should be made by those who will bear the
benefit or
burden of the results. The enlightened
development
worker will
contribute to community understanding through consciousness
raising and
training.
A CHECKLIST FOR DEVELOPING
SUSTAINABLE
AGRICULTURAL PROJECTS
This checklist of concepts helpful for
developing ecologically
sustainable
projects has been prepared to assist you in utilizing the
information
in this book.
* Use land according to its use
capabilities, thus avoid if
possible slopes prone to landslides.
Where these are in use,
maintain cover to conserve the soil.
* Ensure that, with the exception of
edible and useful products
harvested or taken out of the system
from time to time, as
much recycling of materials and wastes
as possible occurs.
* Control pests by biological and
mechanical methods insofar
as possible.
* Utilize local resources, including human
and animal energy,
without increasing the level of
technology significantly
wherever possible.
* Do not overlook local varieties of
crops, and conserve local
wild plants and animals that may be
important food sources,
as well as genetic resources.
* Satisfy local consumption first in
utilizing production.
* Focus on species with multi-use
potentials in combining
nutritional needs (legumes, fruits,
vegetables, animals with
high protein yields per unit weight)
with other uses for
example, crafts, construction materials,
and drugs, especially
in densely populated areas).
* Combine a variety of species with
different properties,
products, and contributions.
* Exploit the full range of ecosystems
which may differ in soil,
water, temperature, altitude, slope,
fertility, etc., within a
field or region.
* Involve community and farmers in the
design, implementation,
management, and evaluation of the
program.
* Involve women, as well as men, in
decision making and
training.
* Include cultural values (religious or
other) and beliefs in the
development of plans for conservation of
species and undisturbed
wild spaces.
* Build upon existing social organizations
and mutual assistance
customs for environmental rehabilitation
and conservation.
* Consider the non-quantifiable and
indirect benefits and costs
in any economic analysis for decision
making.
* In all cases, focus on minimizing
negative impacts while
trying to introduce improvements.
* Check the land tenure problems of the
farmers and include
consideration of them in planning.
* Ensure the program has a sufficiently
long-term horizon.
To this checklist, however, the
development worker may want
to add
others. Other guidelines may be based
on such things as: 1)
the goals or
philosophy of the the local residents and the sponsoring
agency or
individual, and 2) the realities of the context within
which the
project will occur (limits of time, funding, scope).
For small-scale, community-based efforts
that emphasize
low-input
appropriate technology and/or appropriate development
philosophy,
some points that should be considered are:
- optimal use of locally available
material and human
resources
- strong community involvement and support
- community-identified and/or community
realized needs
- high potential for enhancing community
self-reliance in both
short and long-range terms
- technologies that can be taught from one
farmer to another
so that a multiplier effect is achieved
- availability and allocation of funds
- high priority on use and adaptation of
traditional technologies
- necessity to complete activity during a
certain time frame
The sequence
of principles developed by World Neighbors (Bunch
10.2) is
reproduced on the next page. These
principles can help
achieve the
main goals of any agricultural program which are:
- that farmers develop the ability to
solve their own problems
- that they learn about and adapt
appropriate technologies
that build on traditional practices
- that the program achieves early but
relevant success
As boundaries within which the project
must operate regardless
of specific
design aspect, these principles serve two major purposes:
first they
provide a framework for designing projects; second, they
can be used
to enable the planner to make wise choices regarding
feasibility
among possible project designs. For
example, the planner
following
these guidelines knows that any design he or she comes up
with must
include a strong community participation and/or involvement
component;
the planner judging a project against these guidelines
must take a
closer look at an effort which does not indicate
community
support.
<GOALS AND
PRINCIPLES OF SMALL SCALE PROJECTS>
03p138.gif (600x600)
Source:
Bunch 10.2
EXAMPLES OF TRADITIONAL RESOURCE
MANAGEMENT SYSTEMS
The following table provides examples of
resource management
strategies
followed by traditional farmers in developing countries, to
cope with
environmental constraints in a variety of circumstances.
It
is important
that you consider the perspective of traditional systems
that have
already solved some of the resource management questions
raised in the
earlier chapters. (Altieri 10.1)
SOME EXAMPLES OF SOIL,
SPACE, WATER
AND VEGETATION MANAGEMENT
SYSTEMS USED BY
TRADITIONAL
AGRICULTURALISTS
THROUGHOUT THE WORLD
Objectives or
Stabilizing Agricultural
Systems
Environmental
Processes
or Practices
Constraint
Limited
space Maximum utilization
Intercropping, agroforestry,
multistorey
of environmental
cropping, home gardens,
resources and
altitudinal crop zonation,
farm
sources and
fragmentation,
rotations, etc.
land
Steep
slopes Erosion control,
Terracing, contour farming,
living
soil improvement
and dead barriers, mulching,
water
levelling,
continuous crop,
conservation,
diversification and/or fallow cover,
stone walls,
of
integrated land
use (planting so
production
that each crop has
maximum
location
advantage)
Marginal
soil Sustain soil
fertility Natural and/or
improved fallow,
fertility
and recycle
crop rotations and
intercropping
organic
with legumes, litter
gathering,
matter
composting, manuring, green
manuring,
grazing animals in
fallow
fields, night soil and household
refuse, mounding with
hoe, ant
hills used as fertilizer
sites, use
of alluvial deposits,
use of aquatic weeds and
muck,
alley
cropping with legumes,
plowed
leaves, branches, and
other debris, burning
vegetation,
etc.
Flooding or
excess Utilization of
Raised field agriculture
(i.e.,
water
water bodies in
chinampas, tablones), ditched
an integrated
fields, diking, etc.
manner with
agriculture
Salinity
or Lowering of
Planting of appropriate
tree
water
logging water table
species.
due to
high
ground
water
Excess
water Optimum use of
Control of floodwater with
available water
canals and checkdams.
Sunken
fields dug down to ground
water
level. Splash irrigation.
Canal
irrigation
fed from ponded
groundwater, fed
from wells,
lakes,
reservoirs, etc.
Unreliable
rainfall Best utilization
Use of drought tolerant crop
of available
species and varieties,
mulching,
moisture
use of weather
indicators, mixed
cropping
that best utilize end of
rainy season, use of crops
with
short
growing period
Wind
velocity, Microclimatic
Shade reduction or
enhancement,
temperature,
or amelioration
plant spacings, thinning,
radiation
extremes
use of shade tolerant crops, increased
plant
densities, mulching,
management with
hedges,
fences, tree rows; weeding,
shallow
plowing, minimum
tillage, intercropping,
agroforestry
alley-cropping, etc.
Pest
incidence Crop protection
Overplanting, allowing some
(invertebrates,
maintenance of
pest damage, scaring away
vertebrates)
low pest popula-
pests, setting traps, hedging
tion levels
and/or fencing, use of
resistant
varieties, mixed
cropping, enhancement
of natural
enemies,
hunting,
direct picking, use of
poisons,
repellents, planting in
times of
low pest potential, etc.
LONG TERM
EVALUATION OF LOCAL AGRO-ECOSYSTEMS
The long-term performance of local
agricultural systems can be
evaluated by
four properties: (See Conway 10.4)
* Sustainability:
Relates to the ability of an agricultural
system to maintain production through
time in the face of
long-term ecological and/or socio-economic
constraints.
Sustainability of small-scale farming
systems depends on the
accessibility to resource poor farmers
of technologies and
resources.
* Stability:
Expresses the consistency of production of a
cropping system through time under a
given set of environmental,
economic, and management
conditions. Production
trends can be expressed as yield by
area, season, or year.
Both stability and sustainability have
two dimensions--time and
disturbance. These terms
then have two connotations--persistence
and resistance.
Persistence is the tendency of the system
to look the same through time; resistance
is its capacity to
withstand disturbance.
* Resilience:
Relates to the ability of a system to recover from
disturbances of perturbations.
Perturbations can be salinity/acidity
problems, pests, flood/drought, etc.
* Equity:
Is a measure of how equitably the products of the
farm (income, productions, etc.) or
the inputs used (labor,
land, etc.) are distributed among the
local producers and
consumers and between men and women.
ADDITIONAL ASSISTANCE OR INFORMATION
At this or any point in the planning
process, there may be
reasons for
seeking additional assistance. For
example, preliminary
investigation
may show clearly that the area requires access to more
specialized
expertise, as in the case of working with a degraded
watershed.
Consultation with specialists such as local
or regional
water
resource managers, ecologists, sociologists, resource economists
or
agricultural extension officers would be recommended before going
very far with
the planning process.
Second, even when and if the project
seems to be relatively
simple and
easily tackled, it is a good idea to seek an objective
appraisal.
The development worker can do this by
summarizing the
findings to
date, making recommendations based on those findings,
outlining
planned activities, and getting in touch with experts who
are familiar
with community based projects. If
possible, the development
worker should
provide a community profile and natural environment
information.
These can provide an excellent base from
which to
offer assistance even from a distance.
There are a number of other ways to bring
valuable technical
expertise and
insight to the planning process:
* Seek advice from local residents.
Their knowledge of local
conditions and past environmental
impacts is not usually
available elsewhere and is a resource that is much too
important to be overlooked.
* Contact local universities and
government agencies, and local
representatives of international
organizations as well as local
NGOs, churches and missionaries.
Often they have a great
deal of pertinent information on local
soils, climate, terrain,
and upon plants and animals native to
the region. Or they
may have insights and valuable
suggestions about other
resources.
* Using local resource people, organize
an interdisciplinary
team to observe possible project
sites. The team can then
discuss the project from their
respective viewpoints. Collectively,
the team may be able to identify potential
effects that
will have to be accounted for in the
project design. Depending
upon the type of project, the team
might include representatives
from several of these fields:
ecology, hydrology,
soil science, entomology, and so on.
* As planning and investigation continues
locally, get in touch
with other organizations.
Network with nongovernmental
organizations in the area or region.
Through outside assistance the planner
can test the reality and
feasibility
of the project. Some planners may
prefer to have the
project
reviewed only after the needs identification and assessment
process is
complete. Other planners may choose to
have the material
reviewed at
several points. For those who wish to
use such services,
they may be
available locally, or through international non-governmental
organizations.
A list of organizations that can help is
included in
Appendix B.
APPENDIX A
REFERENCES
Chapter
2: The Relation of Agriculture and
Environment
1.
Altieri, M.A.
1987. Agroecology:
The Scientific Basis of
Alternative Agriculture.
Boulder, CO:
Westview Press.
2.
Briggs, D.J.
and F.M. Courtney.
1985.
Agriculture and
Environment.
London: Longman.
3.
Conway, G.R.
1986. Agroecosystem
Analysis for Research and
Development.
Bangkok: Winrock
International Institute for
Agricultural Development.
4.
Cox, G.W. and M.P. Atkins.
1979.
Agricultural Ecology: An
Analysis of World Food Production
Systems. San Francisco, CA:
W.H. Freeman and Co.
5.
Dover, M. and L.M. Talbot.
1987.
To Feed the Earth:
Agroecology for Sustainable
Development. Washington, DC:
World Resources Institute.
6.
King, B.T. et al.
1984. Alley
Cropping: A Stable Alternative to
Shifting Cultivation.
Ibadan, Nigeria:
IITA, 22 p. Permission
granted to reprint figure.
7.
Marten, G.G.
1986. Traditional
Agriculture in Southeast Asia:
A Human Ecology Perspective.
Boulder, CO:
Westview Press.
Permission granted to reprint figure.
Chapter
3: Planning for Sustainable Development
1.
Bryant, C. and L.G. White.
1984.
Managing Rural
Development with Small Farmer
Participation. CT:
Kumarian
Press.
2.
Buhler, R.G., M. Ochoa, and S. Tobing.
"A Primer for Planning
Development Projects."
Interface, Second/Third Quarter 1987.
Washington, DC:
ADRA International.
3.
Buhler, R.G. and K. Flemmer.
"A Primer for Planning
Development Projects - II."
Interface, Fourth Quarter 1987.
Washington, DC:
ADRA International.
4.
Bunch, R.
1982. Two Ears of Corn:
A Guide to
People-Centered Agricultural
Development. Oklahoma City, OK:
World Neighbors.
5.
Chambers, R.
1983. Rural
Development: Putting the Last
First.
London: Longman.
6.
Richards, P.
1984. Indigenous
Agricultural Revolution. Boulder,
CO:
Westview Press.
7.
Rugh, J.
1986. Self-Evaluation:
Ideas for Participatory
Evaluation of Rural Community Development
Projects.
Oklahoma City, OK:
World Neighbors.
8.
Weber, F. with C. Stoney.
1986.
Reforestation in Arid Lands.
Arlington, VA:
VITA. Permission granted
to reprint table.
Chapter
4: Other Considerations for Planning
1.
Brokensha, D. and A.P. Castro.
1984.
Fuelwood, Agro-Forestry,
and Natural Resource Management:
The Development
Significance of Land Tenure and Other
Resource
Management/Utilization Systems.
Binghamton, NY:
Institute
for Development Anthropology.
2.
Collins, J.
1984. Land Tenure, Institutional
Factors and
Producer Decisions on Fragile Lands.
Binghamton, NY:
Institute for Development Anthropology.
3.
Dixon, R.
1980. Assessing the Impact of
Development Projects
on Women.
AID Program Evaluation Discussion Paper No. 8.
Washington, DC:
Agency for International Development.
4.
Dankelman, I. and J. Davidson.
1988.
Women and
Environment in the Third World.
Alliance for the Future.
London:
Earthscan.
5.
Pezzullo, C. 1982.
Women and Development.
Guidelines for
Programme and Project Planning.
Santiago, Chile:
Economic
Commission for Latin America and the
Caribbean, United
Nations.
6.
United Nations.
1980. Rural Women's
Participation in
Development.
Evaluation Study No. 3.
New York: United
Nations Development Programme.
7.
Weinstock, J.A.
1984. Tenure and forest
Lands in the Pacific.
Working Paper.
Honolulu, HI: East-West
Environment and
Policy Institute.
8.
Zimbabwe Women's Bureau.
1981.
We Carry a Heavy Load.
Rural Women in Zimbabwe Speak Out.
Harare, Zimbabwe:
Zimbabwe Women's Bureau.
Chapter
5: Soil Management Through Erosion
Control
1.
Beets, W.C.
1982. Multiple Cropping and
Tropical Farming
Systems.
Boulder, CO: Westview Press,
Inc.
2.
Catholic Diocese of Nakuru.
Report on Sustainable Agriculture
Workshop held at Baraka F.T.C. Molo, July
27 - August 16,
1986.
3.
FAO.
1978. Methodology for Assessing
Soil Degradation.
Rome.
4.
FAO.
1984. Improved Production
Systems as an Alternative to
Shifting Cultivation.
FAO Soils Bulletin 53.
Rome.
5.
Greenland, D.J. and R. Lal.
1977.
Soil Conservation and
Management in the Humid Tropics.
NY:
John Wiley and Sons.
6.
Hudson, N. 1981.
Soil Conservation.
Ithaca, NY: Cornell
University Press.
7.
Poincelot, R.P.
1986. Toward a More
Sustainable Agriculture.
Westport, CT:
AVI Publishing Company.
8.
Sommers, P.
1983. Low Cost Farming in the
Humid Tropics:
An Illustrated Handbook.
Manila, Philippines:
Island
Publishing House, Inc., 38 p.
9.
Troeh, F.R. et al.
1980. Soil and Water
Conservation for
Productivity and Environmental
Protection. Englewood Cliffs,
NJ:
Prentice-Hall.
10. Weber, F.
and M. Hoskins. 1983.
Soil Conservation Technical
Sheets.
Moscow, ID: Forest, Wildlife and
Range Experiment
Station, University of Idaho.
11. Wolman,
M.F. and F.G.A. Fournier. 1987.
Land
Transformation in Agriculture.
SCOPE.
NY: John Wiley and
Sons.
Chapter
6: Water Supply and Management
1.
Darrow, K. and M. Saxeniah.
1986.
Appropriate Technology
Sourcebook, A Guide to Practical Books for
Village and Small
Communities.
Washington, DC:
Volunteers in Asia.
2.
Szeremi, M. and T. Pluer.
Drip Irrigation for Family Garden.
Available from CODEL, Inc.
See Appendix B.
3.
Tillman, R.
1981. Environmental Guidelines
for Irrigation.
Washington, DC:
U.S. Man and the Biosphere Programme and
U.S. Agency for International Development.
4.
Tillman, R.
1981. Environmentally Sound
Small-Scale Water
Projects.
Guidelines for Planning Series.
Arlington, VA:
CODEL/VITA.
Chapter
7: Soil Nutrient Management
1.
Bornemiza, E. and A. Alvarado.
1975.
Soil Management in
Tropical America.
Raleigh, NC:
North Carolina State
University.
2.
Brady, N.C.
1984. The Nature and Properties
of Soils. 9th
edition.
New York, NY: MacMillan
Publishing Co. Permission
granted to reprint figure.
3.
FAO.
1971. Improving Soil Fertility
in Africa. FAO Soils
Bulletin 14.
Rome.
4.
FAO.
1975. Organic Materials as
Fertilizers. FAO Soils
Bulletin 27.
Rome.
5.
FAO.
1977. Soil Conservation and Management
in Developing
Countries.
FAO Soils Bulletin 33.
Rome.
6.
FAO.
1978. Organic Materials and Soil
Productivity. FAO
Soils Bulletin 35.
Rome.
7.
Lal, R.
1987. Tropical Ecology and
Physical Edaphology. NY:
John Wiley.
8.
Rodale Institute.
Composting; Green Manure; Manure Handling.
(pamphlets) Emmaus, PA:
Rodale Press, Inc.
9.
Sanchez, P.A.
1976. Properties and
Management of Soils in the
Tropics.
NY: John Wiley and Sons.
Chapter
8: Pest Management
1.
Altieri, M.A. and D.K Letourneau.
1982.
"Vegetation
Management and Biological Control in
Agroecosystems". Crop
Protection 1:405-430.
2.
Bottrell, D.R.
1979. Integrated Pest
Management. Washington,
D.C.:
Council on Environmental Quality.
3.
Brown, A.W.A.
1978. Ecology of
Pesticides. NY:
John Wiley
and Sons.
4.
Chaboussou, F.
1986. "How
Pesticides Increase Pests." The
Ecologist, Vol. 16, No. 1, p. 30.
5.
Environment Liaison Centre.
1987.
Monitoring and Reporting
the Implementation of the International
Code of Conduct on the
Use and Distribution of Pesticides (The
FAO Code) Final Report.
Nairobi, Kenya:
Environment Liaison Centre.
6.
Flint, M.L. and R. vanden Bosch.
1977.
A Source Book on
Integrated Pest Management.
NY:
Plenum Press.
7.
Flint, M.L. and R. vanden Bosch.
1981.
Introduction to
Integrated Pest Management.
NY:
Plenum Press.
8.
Gips, T. 1987.
Breaking the Pesticide Habit - Alternatives to 12
Hazardous Pesticides.
Minneapolis, MN:
International Alliance
for Sustainable Agriculture.
9.
Hansen, M.
1988. Escape From the Pesticide
Treadmill:
Alternatives to Pesticides in Developing
Countries. Mt. Vernon,
NY:
Institute for Consumer Policy Research Consumers Union.
10. Huffaker,
C.B. and P.S. Messenger. 1976.
Theory and Practice
of Biological Control.
NY:
Academic Press.
11.
International Organization of Consumers Unions.
Problem
Pesticides, Pesticide Problems:
A Citizens' Action Guide to the
International Code of Conduct on the
Distribution and Use of
Pesticides.
Penang, Malaysia: IOCU
Regional Office for Asia
and the Pacific.
12.
Litsinger, J.A. and K Moody. 1976.
"Integrated Pest
Management in Multiple Cropping
Systems." In Multiple
Cropping.
P.A. Sanchez, ed. American Soc.
Ecol. Management
2:
161-168. pp. 293-316.
13. Metcalf,
R.L. and W. Luckman. 1975.
Introduction to Insect
Pest Management.
NY: John Wiley and Sons.
14. Moses, M.
1988.
A Field Survey of Pesticide-Related Working
Conditions in the U.S. and Canada.
Monitoring the
International Code of Conduct on the
Distribution and Use of
Pesticides in North America.
San Francisco, CA:
The Pesticide
Education and Action Project.
15. Nebel,
B.J. 1987.
Environmental Science:
The Way the World
Works.
2nd edition, p. 414. Englewood
Cliffs, NJ:
Prentice-Hall, Inc.
Permission granted to reprint figure.
16. Pimentel,
D. (ed.) 1981. CRC Handbook of Pest
Management in
Agriculture.
Vol. I. Boca Raton, FL:
CRC Press.
17. Rabb,
R.L. and F.E. Guthrie. 1970.
Concepts of Pest
Management.
Raleigh, NC: North
Carolina State University.
18. Reissig,
W.H. et al. 1985.
Illustrated Guide to Integrated Pest
Management in Rice in Tropical Asia.
Manila, Philippines:
International Rice Research Institute.
19. Smith,
R.F. and R. vanden Bosch.
"Integrated control."
In Pest
Control, R.L. Doutt (ed).
NY:
Academic Press, pp. 295-340.
20. vanden
Bosch, R., P.S. Messenger, and A.P. Gutierrez.
1982.
An Introduction to Biological
Control. NY:
Plenum Press.
Chapter
9: Agroforestry Systems
1.
Christanty, L., O. Abdoellah and J.
Iskander. 1986.
"Traditional
Agroforestry in West Java:
The Pekarangan (Homegarden) and
Talun-Kebun (Shifting Cultivation)
Cropping Systems." In
Traditional Agriculture in Southeast Asia,
G. Marten (ed).
Boulder, CO:
Westview Press.
2.
Fortmann, L. and D. Rocheleau.
1985.
Women and
Agroforestry:
Four Myths and Three Case Studies.
Nairobi:
ICRAF, Reprint No. 19.
3.
Gholz, H.L.
1987. Agroforestry:
Realities, Possibilities and
Potentials.
Dordrecht: Martinos
Nijhoff Publishing.
4.
Kamweti, D.
1982. [I\]Tree Planting in
Africa South of the
Sahara.
Nairobi, Kenya: Environment
Liaison Centre.
5.
Kenya Energy Non-Governmental
Organizations. The Value of
Indigenous Trees.
Nairobi, Kenya:
KENGO.
6.
Lal, R.
1987. Tropical Ecology and
Physical Edaphology. NY:
John Wiley and Sons, 732 p.
7.
Lockevetz, W. ed.
1983. Environmentally
Sound Agriculture.
New York, NY:
Praeger Publishers.
Permission granted to
reprint figure.
8.
Mujeres en Desarrollo Dominicana, Inc.
1988.
Cojan la Mocha
Mujeres, Vamos a Reforestar.
Santo Domingo, Dominican
Republic:
MUDE. Permission granted to
reprint drawing.
9.
Nair, P.K.R.
1984. Soil Productivity
Aspects of Agroforestry.
Nairobi, Kenya:
ICRAF.
10. Nair,
P.K.R. 1985.
"Classification of Agroforestry Systems."
Agroforestry Systems 3:97-128.
11. Nair,
P.K.R. 1987.
Agroforestry Systems in Major Ecological
Zones of the Tropics and Subtropics.
Nairobi, Kenya:
ICRAF,
Working Paper No. 47.
12. Spicer,
N. 1987.
"Agroforestry Systems in Zimbabwe."
Paper
prepared for the NGO Agroforestry
Workshop, Nyanga,
Zimbabwe, June 1987.
Based on information from International
Council for Research in Agroforestry,
Kenya and Forestry
Commission, Zimbabwe.
13. Teel,
W. 1984.
A Pocket Directory of Trees and Seeds in Kenya.
Nairobi, Kenya:
KENGO.
14. Vergara,
N.T. 1987.
Agroforestry in the Humid Tropics.
Its
Protective and Ameliorative Roles to
Enhance Productivity and
Sustainability.
Honolulu, HI: Environment
and Policy institute,
East-West Center and Laguna,
Philippines: Southeast Asian
Regional Center for Graduate Study and
Research in
Agriculture.
15. von
Carlowitz, P.G. 1986.
Multipurpose Tree and Shrub Seed
Directory.
Nairobi, Kenya:
International Council for Research
in Agroforestry.
16. Weber, F.
and M. Hoskins. 1983.
Agroforestry in the Sahel.
Blacksburg, VA:
Virginia Polytechnic Institute and State
University.
17.
Wijewardene, R. and P. Waidyanatha.
1984. Conservation
Farming for Small Farmers in the Humid
Tropics. Sri Lanka:
Department of Agriculture, 38 p.
18. Wiersum,
K.F. 1981.
Viewpoints on Agroforestry.
Wagerringen:
Hinkeloord, Agricultural University.
19. Winterbottom
R. and P.T. Hazlewood. 1987.
"Agroforestry and
Sustainable Development:
Making the Connection."
Ambio, Vol.
16 No. 2-3, pp. 100-110.
Chapter
10: Conclusion:
A Checklist for Sustainable
Development,
Examples of Traditonal Systems, and Long
Term
Evaluation.
1.
Altieri, M.A.
1987. Agroecology:
The Scientific Basis of
Alternative Agriculture.
Boulder, CO:
Westview Press.
2.
Bunch, R.
1982. Two Ears of Corn:
A Guide to
People-Centered Agricultural
Improvement. Oklahoma, OK:
World Neighbors.
Permission granted to reprint diagram.
3.
Chambers, R. and B.P. Ghildyal.
1985.
"Agricultural Research
for Resource-Poor Farmers:
The Farmer--First and--Last Model".
Agricultural Administration 20:
1-30.
4.
Conway, G.R.
1986. Agroecosystem Analysis for
Research and
Development.
Bangkok: Winrock
International Institute for
Agricultural Development.
5.
Richards, P.
1984. Indigenous
Agricultural Revolution.
Boulder, CO:
Westview Press.
6.
Tull, K and M. Sands.
1987.
Experiences in Success: Case
Studies in Growing Enough Food Through
Regenerative
Agriculture.
Emmaus, PA: Rodale
International.
7.
Zandstra, H.G. et al.
1981.
A Methodology for On-Farm
Cropping Systems Research.
Los Banos, Philippines:
IRRI.
GENERAL REFERENCES
Carlier.
H. 1987.
Understanding Traditional Agriculture,
Bibliography for Development Workers.
Netherlands:
ILEIA.
Child, R.D.,
H. Heady, W. Hickey, R. Peterson, and R. Pieper.
1984.
Arid and Semiarid Lands, Sustainable Use
and Management in
Developing Countries.
Morrilton, AR:
Winrock International.
Child, R.D.,
H. Heady, R. Peterson, R. Pieper, and C. Poulton.
1987.
Arid and Semiarid Rangelands:
Guidelines for Development.
Morrilton, AR:
Winrock International.
Food and
Agriculture Organization of the United Nations.
1983.
Food and Fruit-Bearing Forest
Species: 1.
Examples from
Eastern Africa, Forestry Paper 44/1;
2. Examples from
Southeastern Asia, Forestry Paper 44/2;
3. Examples from
Latin America, Forestry Paper 44/3.
Rome:
FAO.
Goodland, R.,
C. Watson, and G. Ledec. 1984.
Environmental
Management in Tropical Agriculture.
Boulder, CO:
Westview
Press.
Huston,
P. 1978.
Message from the Village.
NY: The Epoch B
Foundation.
Leonard,
D. 1983.
Traditional Field Crops.
ICE Manual Number
M-13.
Washington, DC: Peace Corps.
Nanda, M.
ed. Resource Guide to Sustainable
Agriculture in the
Third World.
Minneapolis, MN:
International Alliance for
Sustainable Agriculture.
National
Research Council. Ecological Aspects of
Development in the
Humid Tropics.
Washington, DC: National
Academy Press.
Vickery, D.
and J. 1978.
Intensive Vegetable Gardening for Profit
and Self-Sufficiency.
Program and Training Journal, Reprint
Series, Number 25.
Washington, DC:
Peace Corps.
Wade, I.
1986.
City Food. Crop Selection in
Third World Cities.
San Francisco, CA:
Urban Resource Systems, Inc.
APPENDIX B
LIST OF RESOURCE
AGENCIES
ACORDE
Apartado
Postal 163C
Tegucigalpa,
HONDURAS
African NGOs
Environment Network (ANEN)
P.O. Box
53844
Nairobi,
KENYA
APPROTECH
Asia
Ground Floor
Philippine
Social Development Center
Magallanes
Corner Real Street
Intramuros,
Manila
PHILIPPINES
Center for
Education and Technology (CET)
Casilla 16557
Correo 9
Santiago,
CHILE
Centro
Agronomico Tropical de Investigacion y Ensenanza (CATIE)
Turrialba,
COSTA RICA
Coordination
in Development, Inc.
CODEL
475 Riverside
Drive, Room 1842
New York, New
York 10115, USA
Environment
Liaison Centre (ELC)
P.O. Box
72461
Nairobi,
KENYA
ENDA-TM
Environment
and Development in the Third World
SENEGAL
Box 3370
Dakar, SENEGAL
ZIMBABWE
P.O. Box MP 83
Mt. Pleasant
Harare, ZIMBABWE
INADES-FORMATION
African
Institute for Economic and Social Development
IVORY COAST
08 BP 8
Abidjan 08, IVORY COAST
KENYA
P.O. Box 14022
Nairobi, KENYA
Information
Centre for Low External-Input Agriculture (ILEIA)
Kastanjelaan
5
P.O. Box 64
3830 AB
Leusden, THE NETHERLANDS
Institute for
Alternative Agriculture, Inc.
9200 Edmonston
Road, Suyite 117
Greenbelt,
Maryland 20770
Institute for
Consumer Policy Research
Consumers
Union
256
Washington Street
Mt. Vernon,
New York 10553, USA
International
Alliance for Sustainable Agriculture (IASA)
Newman Center
University of
Minnesota
1701
University Avenue, S.E., Room 202
Minneapolis,
Minnesota 55414, USA
International
Council for Research in Agroforestry (ICRAF)
P.O. Box
30677
Nairobi,
KENYA
International
Institute for Environment and Development (IIED)
1717
Massachusetts Avenue, N.W.
Washington,
D.C. 20036, USA
International
Institute of Tropical Agriculture (IITA)
PMB 5320
Ibadan,
NIGERIA
International
Organizaton of Consumers Unions (IOCU)
P.O. Box 1045
10830 Penang,
MALAYSIA
International
Rice Research Institute (IRRI)
P.O. Box 933
Manila,
PHILIPPINES
Kenya
Institute of Organic Farming (KIOF)
Box 34972
Nairobi,
KENYA
Pesticide
Action Network International (PAN)
Regional
Centers:
AFRICA (English)
Environment Liaison Centre
P.O. Box 72461
Nairobi, KENYA
AFRICA (French)
ENDA/PRONAT
B.P. 3370
Dakar, SENEGAL
ASIA/PACIFIC
International Organization of Consumers
Unions
Regional Office
P.O. Box 1045
10830 Penang, MALAYSIA
EUROPE
PAN-Europe
22, rue des Bollandistes
1040 Brussels, BELGIUM
LATIN AMERICA
Fundacion Natura
Casilla 243
Quito, ECUADOR
NORTH AMERICA
Pesticide Education and Action Project
P.O. Box 610
San Francisco, California
94101, USA
Rodale
Institute
222 Main
Street
Emmaus, Pennsylvania
18098, USA
Sahabat Alam
Malaysia (Friends of the Earth)
37 Lorong
Birch
Penang,
MALAYSIA
Volunteers in
Technical Assistance (VITA)
1815 North
Lynn Street, Suite 200
Arlington,
Virginia 22209, USA
APPENDIX C
GLOSSARY
absorb - To
suck in as in a blotter.
adsorb - To
adhere to the surface of as ions on molecules.
aerial
biomass - Total weight and molecules of living materials.
aquifer - An
underground layer of rock that is porous and permeable
enough to
store significant quantities of water.
artificialities
- Mechanisms, techniques, and processes introduced
by humans.
biodegradable
- Refers to substances that can readily be decomposed
by living
organisms.
biodiversity
- The critical multiplicity of species that creates and
maintains
ecosystems.
biomass - The
total weight of all the living organisms in a given
system.
biotic -
Living or derived from living things.
capillary
action - The movement of water upward against the force
of gravity,
through small openings. The liquid is
pulled upward by
electrical
attractions between the water molecules and the sides of
the holes.
carrying
capacity - The maximum number of individuals of a given
species that
can be supported by a particular environment.
climax
community - A natural system that represents the end, or
apex, of an
ecological succession.
colloidal -
Made up of solid, liquid, or gaseous substances of very
small,
insoluble particles.
denitrification
- Reduction of nitrates to gaseous state by certain
organisms
that produces nitrogen.
desertification
- The process whereby lands that have been disturbed
by natural
phenomenon (e.g., drought, flooding) or people
initiated
processes (e.g., improper farming practices) are converted to
deserts.
double
cropping - Growing two crops in the same year in sequence,
seeding or
transplanting one after the harvest of the other (same
concept for
triple cropping).
ecological
niche - The description of the unique functions and
habitats of
an organism in an ecosystem.
ecosystem - A
group of plants and animals occurring together plus
that part of
the physical environment with which they interact.
An
ecosystem is
defined to be nearly self-contained, so that the matter
flowing into
and out of it is small compared to the quantities that
are
internally recycled in a continuous exchange of the essentials of
life.
eutrophication
- The enrichment of a body of water by nutrients,
with the
consequent deterioration of its quality for human purposes.
evaporation -
Vaporization of water from surfaces.
evapotranspiration
- The conversion of liquid water to water vapor
by
transpiration followed by evaporation from the leaf surface.
externalities
(economic) - The portion of the cost of a product that
is not
accounted for by the manufacturer but is borne by some other
sector of
society. An example is the cost of
environmental degradation
that results
from a manufacturing operation.
farming
system - The manner in which a particular set of farm
resources is
assembled within its environment, by means of technology,
for the
production of primary agricultural products.
This definition
thus excludes
processing beyond that normally performed on the
farm for the
particular crop or animal product. It
includes farm
resources
used in marketing the product.
food chain -
An idealized pattern of flow of energy m a natural
ecosystem.
In the classical food chain, plants are
eaten only by
primary
consumers, primary consumers are eaten only by secondary
consumers,
secondary consumers only by tertiary consumers, and so
forth.
See also food web.
food web -
The pattern of food consumption in a natural ecosystem.
A given
organism may obtain nourishment from many different
trophic
levels and thus give rise to a complex, interwoven series of
energy
transfers.
green
revolution - The realization of increased crop yields in many
areas owing
to the developing of new high-yielding
strains of wheat,
rice, and
other grains in the 1960s. The second
green revolution is
use of the
techniques of genetic engineering to improve agricultural
yields.
groundwater -
Water that has accumulated in the ground and is
replenished
by infiltration of surface water.
growing
season - Used in a general way to refer to the period of
the year when
(most) crops are grown, e.g. the rainy season.
growth cycle
- The period required for an annual crop to complete
its annual
cycle of establishment, growth and production of harvested
part.
habitat -
Place where plant or animal lives.
hectare - A
metric measure of surface area. One
hectare is equal to
10,000 sq. m.
or 2.47 acres.
herbicide - A
chemical used to control unwanted plants.
humus - The
complex mixture of decayed organic matter that is an
integral part
of healthy soil.
hydrological
cycle (water cycle) - The way water moves in a
cycle in all
its forms, on the earth.
infiltration
- The process whereby water filters or soaks into soil as
opposed to
running off the surface.
intercropping
- Two or more crops grown simultaneously in the
same,
alternate, or paired rows in the same area.
laterite - A
soil type found in certain humid tropical regions that
contains a
large proportion of aluminum and iron oxides and only a
small
concentration of organic matter. Laterite
soils cannot support
sustained
agriculture.
leaching -
The extraction, usually by water, of the soluble components
of a mass of
material. In soil chemistry, leaching
refers to
the loss of
surface nutrients by their percolation downward below the
root zone.
legume - An
plant of the family Leguminosae, such as peas, beans,
or
alfalfa. Bacteria living on the roots
of legumes change atmospheric
nitrogen,
[N.sub.2], to nitrogen-containing salts that can be readily
assimilated
by most plants.
limiting
factors (law of) - A biological law that states that the
growth of an
organism (or a population of organisms) is limited by
the resource
that is least available in the ecosystem.
litter - The
intact and partially decayed organic matter lying on top
of the soil.
mineralization
- The process of gradual oxidation of organic matter
present in
soil that leaves just the gritty mineral components of the
soil.
mixed
cropping - Two or more crops are grown simultaneously in
the same
field at the same time, but not in row arrangements.
(Sometimes
called mixed intercropping.)
monoculture
planting - Growing a single crop on the land at one
time,
particularly the repetitive growing of the same crop on the
same land
year after year.
mulch -
Leaves, straw, peat moss, or other material spread around
plants to
prevent evaporation of water from soil and roots.
multiple
cropping - Growing more than one crop on the same land
in one
year. Within this concept there are
many possible patterns of
crop
arrangement in space and time.
natural
selection - A series of events occurring in natural ecosystems
that
eliminates some members of a population and spares those
individuals
endowed with certain characteristics that are favorable
for
reproduction.
organic
farming - A system of farming using no chemical fertilizers
or
pesticides.
outputs - The
products (for rainfed agriculture, crops), services (e.g.
water supply,
recreational facilities) or other benefits (e.g. wildlife
conservation)
resulting from the use of land.
percolation -
The process of water seeping through cracks and
pores of soil
and rocks.
photosynthesis
- The process by which chlorophyll-bearing plants
use energy
from the Sun to convert carbon dioxide and water to
sugars.
pollution -
The impairment of the quality of some portion of the
environment
by the addition of harmful impurities.
population -
The breeding group to which an organism belongs in
practice.
A population is generally very much smaller
than an entire
species,
because all the members of a species are seldom in close
proximity to
each other.
predator - An
animal that attacks, skills, and eats other animals;
more broadly,
an organism that eats other organisms.
primary
consumer - An animal that eats plants.
rainfed
farming - The growing of crops or animals under conditions
of natural
rainfall. Water may be stored in the
crop field by bunding,
as with
lowland rainfed rice, but no water is available from
permanent
water storage areas.
salinization
- When irrigation water is applied to farmlands, much
of it
evaporates, leaving the salts behind.
Salinization is the process
whereby these
minerals accumulate until the fertility of the soil is
severely
impaired.
shifting
cultivation - Several crop years are followed by several
fallow years
with the land not under management during the fallow.
The shifting
cultivation may involve shifts around a permanent
homestead or
village site, or the entire living area may shift location
as the fields
for cultivation are moved.
slash and burn
- A specific type of shifting cultivation in high
rainfall
areas where bush or tree growth occurs during the fallow
period.
The fallow growth is cleared by cutting and
burning.
soil-moisture
belt - The layer of soil from which water can be
drawn to the
surface by capillary action.
soil
structure - The manner in which soil particles are loosely stuck
together to
form larger clumps and aggregates usually with considerable
air space in
between.
strip
cropping - Growing two or more crops in different strips
across the
field wide enough for independent cultivation.
The strips
are wide
enough to give greater association among the crops in the
strips than
between the different crops.
structural
diversity - A measure of the way in which the canopy
or soil cover
is organized in layers in a cropping or forestry system.
substrate -
The foundation provided by the soil to support plant
growth.
succession -
The sequence of changes through which an ecosystem
passes during
the course of time. Primary succession
is a sequence
that occurs
when the terrain is initially lifeless, or almost so.
Secondary
succession is the series of community changes that takes
place in
disturbed areas where some regrowth is taking place.
surface water
- Includes all bodies of water--lakes, rivers, ponds,
streams - on
the surface of the earth in contrast to ground water that
lies below
the surface.
sustainable -
A measure of the constancy of agricultural production
in the long
term.
sustainable
use - Continuing use of land without severe or permanent
deterioration
of the resources of the land.
symbiotic -
The intimate association of two organisms that provides
a mutual
benefit to both.
temperature
inversions - A meteorological condition in which the
layers of
cool air remain stagnant leading to concentration pollutants.
threshold -
The level of population of insect pests beyond which any
increase will
cause damage.
threshold
level - The minimal dose of a toxic substance that causes
harmful
effects.
toxic
substance - Any substance whose physiological action is
harmful to
health.
transpiration
- The passage of water through the tissues of plants,
especially
through leaf surfaces.
trophic level
- Level of nourishment. A plant that
obtains its
energy
directly from the sun occupies the first level and is called an
autotroph.
An organism that consumes the tissue of an
autotroph
occupies the
second trophic level, and an organism that eats the
organism that
had eaten autotrophs occupies the third trophic level.
vector - An
animal, such as an insect, that transmits a disease - producing
organism from
one host to another.
volatilization
- Process of a liquid or solid becoming gaseous.
water
pollution - The deterioration of the quality of water that
results from
the addition of impurities.
ABOUT THE AUTHOR
Miguel
Altieri is an Associate Professor and Associate Entomologist
at the
University of California, Berkeley. Dr.
Altieri, a native of
Chile, earned
a Ph.D. in Entomology at the University of Florida in
1979 and
studied agronomy and agroecology in Latin America.
Dr. Altieri's
research has centered on methods to enhance naturally
occurring and
introduced biological control agents of pests, and
interactions
of plants and pests, in annual agricultural systems and
orchards.
His research has been based in North, South,
and Central
America.
Dr. Altieri
has published extensively in the fields of agroecology,
sustainable
agriculture, entomology, alternative agriculture, and pest
management.
Among his publications are the following
books:
Agroecology:
The Scientific Basis of Alternative
Agriculture, Weed
Management in
Agroecosystems: Ecological Approaches,
and Agroecology
and Small
Farm Development.
ABOUT THE EDITOR
Since 1977,
Helen Vukasin has been active in the field of environment
and
development. In 1979 she became
associated with CODEL
and helped to
develop the CODEL Environment and Development
Program.
Working with indigenous organizations in
developing
countries,
the Program fosters natural resource management in
small-scale
development projects particularly emphasizing people's
participation
in the process.
In addition
to serving as a consultant to CODEL, Ms. Vukasin is
currently a
Program Associate with the Development Institute of the
University of
California at Los Angeles. She is
actively interested in
gender issues
in natural resource management and in contributing to
knowledge
about ways to foster people's participation in development
and
environment activities.
========================================
========================================
