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                          TECHNICAL PAPER #26
                           Dr. Glen M. Wood
                          Technical Reviewers
                          Charles A. Francis
                          Armin R. Grunewald
                   1600 Wilson Boulevard, Suite 500
                     Arlington, Virginia 22209 USA
                 Tel: 703/276-1800 . Fax: 703/243-1865
                    Understanding Multiple Cropping
                          ISBN: 0-86619-228-X
              [C]1985, Volunteers in Technical Assistance
This paper is one of a series published by Volunteers in Technical
Assistance to provide an introduction to specific state-of-the-art
technologies of interest to people in developing countries.
The papers are intended to be used as guidelines to help
people choose technologies that are suitable to their situations.
They are not intended to provide construction or implementation
details.  People are urged to contact VITA or a similar organization
for further information and technical assistance if they
find that a particular technology seems to meet their needs.
The papers in the series were written, reviewed, and illustrated
almost entirely by VITA Volunteer technical experts on a purely
voluntary basis.  Some 500 volunteers were involved in the production
of the first 100 titles issued, contributing approximately
5,000 hours of their time.  VITA staff included Maria Giannuzzi
as editor, Julie Berman handling typesetting and layout, and
Margaret Crouch as project manager.
The author of this paper, VITA Volunteer Dr. Glen M. Wood, is
Agronomist and Professor of Plant and Soil Science at the University
of Vermont.  The reviewers are also VITA Volunteers.  Charles
A. Francis, international program director at the Rodale Research
Center in Pennsylvania, has worked on intercropping for the past
10 years.  He was previously a staff scientist at the Centro
Internacional de Agricultura Tropical (CIAT), near Cali, Colombia,
and a professor at the University of Nebraska.   Armin R.
Grunewald bas 33 years experience as a soil scientist with the
U.S. Agency for International Development and the U.S. Department
of Agriculture.  He has performed consultancies in several developing
VITA is a private, nonprofit organization that supports people
working on technical problems in developing countries.   VITA offers
information and assistance aimed at helping individuals and
groups to select and implement technologies appropriate to their
situations.  VITA maintains an international Inquiry Service, a
specialized documentation center, and a computerized roster of
volunteer technical consultants; manages long-term field projects;
and publishes a variety of technical manuals and papers.
                  By VITA Volunteer Dr. Glen M. Wood
Multiple cropping, simply defined, is the growing of two or more
crops on the same field during the same year.   When the crops are
grown one after another the term "sequential cropping" is applied.
If the second or later crops are the result of regrowth of
the first crop, then the term "ratoon cropping" is used.  Sugar
cane (Saccharum spp.), sorghum (Sorghum spp.), and even rice
(Oryza sativa L.) can be ratoon cropped.   Crops that produce no
regrowth, as in the case of most annuals, cannot be ratoon
When two or more crops are grown simultaneously on the same plot
of land the term "intercropping" is appropriate.  Such crops may
be mixed planted, that is, the plants of different crops are
intermingled; or they may be sole (pure stand) planted in alternating
rows, that is, the plants of each crop are grown in separate
rows or strips (wide rows).  When one crop is interplanted
with a second crop as the first crop approaches maturity, the
practice is termed "relay cropping." All of these cropping practices
come under the general heading of multiple cropping.
All forms of multiple cropping have the potential to utilize the
soil more efficiently, resulting in greater production from a
given unit of land.  This is especially true in tropical or subtropical
areas of the world with wet and dry seasons.   Where water
for irrigation is available, exploitation of the abundant solar
energy in the dry season is possible.   Double, triple, and even
quadruple cropping has dramatically increased food production in
some countries--making them exporters instead of importers of
food crops.  Less dramatic increases can also result from other
forms of multicropping.  Beans (Phaseolus vulgaris L.), for example,
can complete their life cycle in dry periods, if fertilized
and relay planted in corn or maize (Zea mays L.) toward the end
of the wet season.
The exploding world population continues to place a severe strain
on existing land resources and their ability to provide enough
food.  Any technology that can result in increased food production
from present land holdings has great potential for easing hunger
around the world.  Some researchers consider multiple cropping the
most important of today's agricultural practices.   Both high and
low technology societies can profit from greater use of multiple
Multicropping is not a new agricultural technique.   Evidence of
the practice has been found in Egypt dating back to 300 B.C.  The
Maya Indians in Central America and the Incas in South America
practiced both sequential and intercropping.
Sequential cropping, to be used most effectively, requires the
use of fertilizers, high yielding plant varieties, pest control,
high planting rates, mechanization, and, where appropriate, irrigation.
Sequential cropping of plants with relatively short growing
seasons offers better total annual use of land than does a
single crop system.  It is particularly important to use the
improved, early maturing, high yielding varieties.   Unlike traditional
varieties, these improved types do not lodge, or fall over
to the ground, when heavily fertilized and also produce more
grain per unit of fertilizer applied.   Pest control, as well as
irrigation and fertilizers, allows them to yield more nearly at
their full potential.
Mechanization, or the use of appropriate mechanical equipment,
allows the farmer to perform promptly all the operations of soil
preparation--planting, pest control, and harvesting--so that the
next crop in sequence is not delayed and a portion of the growing
season wasted.  In the United States and other more temperate
regions of the world where growing seasons are shorter, notillage
planting is widely used.  With the use of specially designed
equipment and early maturing varieties, crops can be
planted in the stubble of a previous crop without any further
soil preparation.  This ensures a minimum of delay and full use of
the available growing season.   Leaving the stubble in place also
minimizes water and wind erosion and affords protection for the
newly emerging seedlings.
The use of day-neutral varieties--those not requiring a specific
day length to flower and set seed--allows the farmer to grow them
at any time of the year, regardless of latitude, if growing
conditions are favorable.  The availability of water for irrigation
permits full use of the dry season.
Early maturing varieties may also suffer less damage from pests.
As a general rule, the most serious crop loss due to weeds occurs
during the first third of the life cycle.   An exception occurs
where late maturing varieties compete better with barnyard grass
(Echinochloa crusgalli L. Beauv.).   Although crop rotation with
different crops will generally result in better pest control, it
may be feasible to rotate different varieties of the same crop
having different disease and insect resistance and better ability
to compete with weeds.  Sometimes natural predators of pests
(biological control) build up to more effective levels when same
crop follows same crop.  The buildup of the pests with continuous
cropping is perhaps more likely to happen, however, and thus
rotation with different crops is preferred.
The principles involved in ratoon cropping, a form of sequential
cropping, are different from other types of multiple cropping
because of such factors as the presence of a well developed root
system, earlier maturity, and the perennial nature of the plant.
Although the term may be applied to perennial pasture plants, it
is considered more appropriately used with respect to field crops
such as sugar cane, sorghum, banana (Musa sapientum, M. caven-dishii),
cotton, kodra millet (Paspalum scrobiculatum), pineapple
(Ananas comosa), and rice.
The advantages of ratoon cropping include the following:
  1. reduced cost of production through savings in land preparation
     and care for the plant;
  2. reduced crop cycle: crop planted less often, so replanting
     cycle is longer;
  3. better use of growing season;
  4. higher yield per unit area in a given period of time;
  5. less use of irrigation water and fertilizer than main (original)
     crop because of a shorter growing period; and
  6. simple and effective way to provide windbreaks for vegetable
On the other hand, ratoon cropping has a number of drawbacks.
These include:
  1. later crops have lower yields than the first crop;
  2. buildup of insect pests;
  3. buildup of harmful weeds;
  4. increased disease problems;
  5. greater cost per unit produced;
  6. where heavy equipment is used, the soil may become hard,
     causing poor drainage and lack of oxygen for roots;
  7. loss of crop density (number of plants per unit of land);
  8. growth of volunteer seedlings inferior to sown variety.
Intercropping requires only 60-80 percent of the land to equal
the production of monocropping systems.   Traditional farmers in
many parts of the world-have practiced intercropping in various
forms for many centuries.  This form of multiple cropping, which
generally involves the growing of rain-fed crops in mixtures,
uses available resources and permits farmers to maintain low but
often adequate and relatively steady production.
Intercropping can take any of three forms--strip planting, row
planting, or mixed planting.   The form chosen should be based on
crops grown and such factors as ease of planting, weeding, and
harvesting.  Yield also may be affected.  Intercropping is particularly
suited to those situations where labor is abundant and land
is not.  If it is to be successful economically, the sum of the
competition of the interplanted species should be less than when
the species are grown alone.   Crops of different maturities have
varying peak requirements for water, fertilizer, light, and
space.  Thus, there may be less competition between different
crops than there is in a sole planting of identical plants.
Moreover, disease and insect infestation of intercropped plants
tends to be less.  For example, virus diseases may spread more
easily through adjacent plants than to those separated by unlike,
and frequently non-susceptible, neighboring plants.   Insects that
spread disease are also thwarted or at least slowed. Insects
tend to be less attracted to plants that are intermingled with
other species than to those in solid stands of the same species.
Interplanting of some crop species, however, may be harmful
because of allelopathic effects.   Allelopathy is defined as "any
direct or indirect harmful effect that one plant has on another
through the production of chemical compounds that escape into the
environment."(*) The harmful compound may take varied forms such
as volatile chemicals produced by roots, or leached from leaves.
Dead or decaying plant tissues may also be a source of allelopathic
substances.  Note that the nitrogen released from legumes
is not considered a form of allelopathy.
Some common combinations are maize-bean, maize-soybean (Glycine
max L. Merr.) , maize-rice, maize-sorghum, sorghum-millet, sweet
potato (Ipomoea batatas Lam.) in sugar cane (Saccharum officinarum
L.), and cotton (Gossypium sp.) with peanuts (Arachis hypogaea
L.).  The net result of such combinations can vary widely from
productive to unproductive compared to sole planting of the same
crops.  Factors such as fertilization schedule, seeding rate and
spacing, selection of variety and type of plant, e.g., dwarf
versus normal (maize), bush versus pole (bean), as well as many
other cultural factors can markedly influence results. <see figure>

umc1x6.gif (600x600)

The overall advantages of intercropping include the following:
  1. provides increased protection against erosion;
  2. insures against crop failure;
  3. spreads labor and harvesting more evenly during the growing
     season and helps minimize storage problems;
  4. helps allocate space for crops required in small quantities,
     and facilitates production of many commodities in a limited
  5. results in efficient use of resources by plants of different
     heights, rooting systems, and nutrient requirements;
  6. where legumes are grown with grasses (or other non-legumes),
     grasses may benefit from the nitrogen fixed by the
     legume companion crop; and
  7. inhibits the spread of diseases and pests since not all
     crops involved are susceptible to the same extent to the
     same problems.
(*) B.R. Trenbath, "Plant Interactions in Mixed Crop Communities,"
Multiple Cropping, Edited by M. Stelly (Madison, Wisconsin:
American Society of Agronomy, 1976).
Disadvantages, on the other hand, are:
  1. mechanized planting and harvesting are difficult;
  2. it is more difficult to apply needed fertilizers and other
     chemicals as in sole cropping; and
  3. experimentation with intercropping is more complex and difficult
     to manage than with sole cropping.
Relay intercropping is a common practice in wet-dry climates
where the wet season is not sufficiently long for two full season
crops.  Generally corn is the wet season crop, with beans interplanted
as the corn approaches maturity.   With relay planting,
greater crop density and protection against wind and water erosion
are achieved.  Since the first crop has reached maturity, its
demands on soil moisture and fertility are minimal as natural
aging and deterioration of leaves occur.   The relay interplanted
seedling crop likewise places small but increasing demands on the
soil.  As the first crop gradually fades out of the picture and is
finally removed entirely through harvest, the sequential crop
continues to advance and the transition is completed.
Multiple cropping in some form can help get the maximum crop
production from fixed land holdings, particularly in subtropical
and tropical areas of the world.   Both low and high technology
societies can profit by adopting one or more of the various
multicropping techniques.  Even small farmers who lack the capital
to purchase inputs (e.g., equipment, fertilizers, herbicides)
but generally have abundant hand labor, can find the practice of
some form of multicropping to be to their benefit.
Multiple cropping places heavy demands on the soil and cannot be
successful unless the crop is supplied with adequate fertilizer.
Where the extra fertilizer is not available, a few crops with low
fertilizer needs may be planted (such as cassava [Manihot sp.]
and plantain [Plantago sp.]).   Many marginal farmers find the
purchase of inorganic fertilizers beyond their means, even if
obtainable, and should not consider intensive multicropping systems.
More limited multicropping can be practiced where substantial
amounts of animal manure and/or composted plant materials
are available.  Minerals provided by burning cleared land have
only temporary value.  On the other hand, many systems of multicropping
originated under subsistence farming and can be made to
work using available sources of fertilizer.   Placing fertilizer in
bands between plants or directly in the planting hole are two
ways of making more efficient use of fertilizer at hand.  Where
possible, legumes should be planted for their ability to obtain
nitrogen from the air and convert it into forms available to
plant roots.
The advantages of multicropping include greater use of available
solar energy in the dry season, improved pest control, greater
insurance against crop failure, better nutritional balance for
families because a wider variety of foods is produced, and a more
stable farm income.
As in any departure from traditional methods, some cautions and
hazards may be encountered in switching from mono- to multicropping.
Farmers should consider their options carefully and seek
help if necessary from local extension agencies or from technical
assistance services such as VITA.
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    Microclimate Relationships in Multiple Cropping Systems." In
    Multiple Cropping, p. 171. Edited by M. Stelly. Madison,
    Wisconsin: American Society of Agronomy, 1976.
Andrews, D.J., and Kassam, A.H. "The Importance of Multiple Cropping
    in Increasing World Food Supplies." In Multiple Cropping.
    Edited by M. Stelly. Madison, Wisconsin: American
    Society of Agronomy, 1976.
Beets, Willem C. Multiple Cropping and Tropical Farming Systems.
    Boulder, Colorado: Westview Press, 1982.
Litsinger, J.A., and Moody, K. "Integrated Pest Management in
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    Edited by M. Stelly. Madison, Wisconsin: American Society
    of Agronomy, 1976.
Metcalf, D.S., and Elkins, D.M. Crop Production, Principles and
    Practices. New York, New York: MacMillan Publishing Co.,
    Inc., 1980.
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Oelsligle, O.D.; McCollum, R.E.; and Kang, B.T. "Soil Fertility
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    p. 281. Edited by M. Stelly. Madison, Wisconsin:
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    Brady. New York, New York: Academic Press, 1970.
Rice, E.L. Allelopathy. New York, New York: Academic Press, 1974.
Thomas, G.W.; Curl, S.E.; and Bennett, W.F. Food and Fiber for a
    Changing World. Danville, Illinois: Interstate Printers and
    Publishers, Inc., 1976.
Thomas, G.W., and Phillips, S.H. "Multiple Cropping--Ace in the
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    Enough Food?, p. 68. Edited by J. Hayes. Washington, D.C.:
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