Chapter Two Fertilizers

1. Definition of fertilizers

In the previous chapter, it was stated that one way of making the soil fertile is through the application of fertilizers. Fertilizers improve the quantity and quality of the produce. To grow well, plants require several elements which are divided into two major groups. The first group consists of nine elements that are required by the plants in large quantities. These are carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, magnesium, calcium and sulphur. The second group consists of eight elements which are required by plants in small quantities. These are iron, boron, molybdenum, copper, zinc, chlorine and cobalt. Some of these elements may be available in air but many of them are found in fertilizers. Those found in air are carbon, hydrogen, oxygen and nitrogen. The remaining elements are available in fertilizers. Every element has a unique role in the growth of the plant.

2. Types of fertilizers

Fertilizers are classified into two major groups - artificial fertilizers and natural fertilizers.

(a) Artificial fertilizers

These originate from either natural minerals that are dug from the soil or from minerals which are industrially manufactured. They are grouped into four categories:

(i) Nitrogen fertilizers.

(ii) Phosphorus fertilizers.

(iii) Potassium fertilizers.

(iv) Mixed fertilizers - packaged after being blended in a special ratio of nitrogen to phosphorus to potassium.

(b) Natural fertilizers

These are made from animal and plant sources. They are passed out as left-overs in the form of either dung or urine. The fertilizers in this category include:

(i) droppings from poultry, birds and the smaller animals;
(ii) ashes;
(iii) left-overs from carcases;
(iv) fertilizers from green plants;
(v) cow dung; and
(vi) compost manure.

3. Differences between artificial and natural fertilizers

Characteristic	Artificial fertilizers	Natural fertilizers
(a) Ease in making.	Difficult for farmers to make. They are made in specialized industries or extracted from the earth.	Easy to be make. Every farmer can make them.
(b) Cost of purchasing.	Very high.	Low and in most cases there are no costs.
(c) Ease in its being used by plants.	Used slowly and take a long time to be used and exhausted in one season.	Easily found and quickly exhausted in the soil.
(d) Quantity of element per unit of weight.	High.	Low. For this reason, one needs large amounts of fertilizer in order to get the quantities of elements required.
(e) Danger to the soil.	Very high if the farmers do not heed advice from agricultural experts.	None.
(0 Danger to plant life.	High if the farmer does not heed advice from agricultural experts.	None.
(g) Difficulty in storage.	Need great care since they easily become damp and get ruined.	Do not require as great care as artificial fertilizers. However, there is a need to protect them away from sunshine and rain.
(h) Potential for changing soil characteristics.	Fertilizers containing calcium reduce soil acidity. However, those with ammonium sulphate raise soil acidity. The other types of fertilizers neither raise nor reduce soil acidity and alkalinity.	None.

Natural fertilizers enable the soil to nourish the crops by:

i) Enhancing soil structure, for example, by changing clay soil into loam soil.

ii) Reducing soil erosion by uniting loose particles, including those of the sandy soil.

iii) Regulating soil temperature for plant growth.

iv) Enabling the soil to retain the amount of water required by plants.

v) Increasing humus in the soil and this, in turn, gives soil a dark colour.

vi) Ensuring life and prosperity for soil organisms which are very important to the farmer.

4. Relationship between quality of soil and yield

Soil may be likened to a dairy cow. If the owner does not feed the cow, the quantity of the milk produced on the first day will be less. If this goes on for a long time, eventually the cow will not produce any milk. The cow will progressively weaken, ail and finally die of either hunger or disease.

Likewise, if the soil is not fertilized for several seasons, the quantity and quality of the yield will progressively decrease until there is no more produce. This happens due to various reasons:

(a) The soil is lacking in many of the elements necessary for the growth of plants.

(b) The soil structure is impaired for lack of humus and loss of the ability to retain water and adequate temperature.

(c) Many of the micro-organisms in the soil that are useful to the farmer have died due to lack of nourishment from natural fertilizers.

5. Relationship between artificial and natural fertilizers

Research has established that artificial fertilizers are faster than natural fertilizers in bringing about results, and in giving higher and better yields. However, the crop is even better when the two types of fertilizers are used jointly rather than singly. All the same, artificial fertilizers are too expensive to be affordable to the majority of farmers. Besides, the country cannot provide adequate quantities of artificial fertilizers for lack of sufficient foreign currency. Therefore, what every farmer can afford are natural fertilizers and some of these, which include compost manure, can be made by the individual. In the following chapters, suggestions are made on how to make and use compost manure.