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close this bookLearn how to Make and Use Compost Manure in Farming (Friends-of-the-book Foundation, 1992, 54 p.)
View the document(introduction...)
View the documentIntroduction
View the documentChapter One Soil
View the documentChapter Two Fertilizers
View the documentChapter Three Using Animal and Plant Sources to Make Compost Manure
View the documentChapter Four Basic Requirements for Preparing Compost Manure
View the documentChapter Five Structure of the Compost Heap and Major Methods of Preparing Manure
View the documentChapter Six Summary of Characteristics and Benefits of the Use of Compost Manure
View the documentBibliography
View the documentBack cover

Chapter Four Basic Requirements for Preparing Compost Manure

As explained in Chapter Three, compost manure results from the breaking down of the refuse by a large number of micro-organisms in the soil in an environment that has adequate moisture, warmth, and oxygen, where the ratio between the carbon and nitrogen in the left-overs is 35 to 1. In these conditions, micro-organisms use the atmospheric oxygen and food from the left-overs and give out carbon dioxide, moisture and energy. This means that for the farmer to make the best compost manure, it is necessary to ensure that the agents of decomposition are given the right surroundings. In the remaining part of this chapter, we will discuss the important requirements that the maker of compost manure should understand and follow.

1. Refuse

Refuse or decomposing matter is the source of food for micro-organisms. It is refuse that has to decompose for the farmer to get compost manure. In setting out what ought to be done, there are several factors that need to be considered.

(a) Availability of nitrogen

Without adequate nitrogen in the refuse heap, micro-organisms cannot effect the decomposition process. It is, therefore, necessary to ensure that there is a good ratio of carbon to nitrogen in the stack of refuse, the initial ratio required being 35 to 1. If the ratio exceeds this, the process of oxidation will be lengthy before enough carbon is released. If it is less, the essential nutrient-nitrogen will escape into the atmosphere as ammonia gas. It should be understood clearly why this ratio between carbon and nitrogen is essential in the making of compost manure. Every fertilizer that results from the decomposition of plant left-overs consists of carbon and nitrogen. However, as plants grow and harden, it becomes more difficult for micro-organisms to cause decomposition. In such plants there is a lot of carbon but only a little nitrogen, which is not easily available to micro-organisms. This means that the refuse resulting from such plants will not decompose at a good rate. Hence, if the heap to be decomposed lacks nitrogen, its decomposition will be slow or the process will not be complete. In such cases, there is need for the introduction of other sources of nitrogen, an event that will enable the micro-organisms to breakdown the carbon in the refuse heap into small particles. There are three such sources, two of which can be easily found:

(i) Manure from livestock

An example of this manure is fresh droppings from goats, sheep, pigs, horses and poultry. This waste matter contains nitrogen.

Fig. 5: Some common sources of nitrogen (legumes)

(ii) Legumes

Examples of legumes are beans, pigeon peas and soya beans. These plants have nitrogen in the nodules on their roots as well as in their leaves.

(iii) Artificial fertilizers

Farmers may also use artificial fertilizers such as ammonium sulphate. Its usage will not be emphasized in this book but this is an easy source of nitrogen for farmers who are able to acquire it.

(b) Capability of refuse to decompose

Everything in the refuse heap should be able to decompose. Naturally, any refuse will eventually decompose.

The following is a list of things capable of decomposing if they are in a heap:

(i) Left-overs of crops after harvesting, for example stems, branches and leaves from legumes, bananas, grains, raw coffee-berry skins, etc.

(ii) Saw dust.

(iii) Mixture of livestock dung, urine and hay in animal sheds.

(iv) Livestock dung.

(v) Vegetable remains after harvesting as well as chippings from plants. However, big remnants of cabbages or other vegetables should be chopped into small pieces or crushed before being heaped. This will hasten its decomposition. Where the roots are intended to decompose, soil must be removed as it slackens the decomposition process.

(vi) Ashes from the kitchen.

(vii) Trimmings from tree hedges.

(viii) Weeds, especially from gardens. These are important as they contain microelements. However, roots and stems of destructive weeds such as strangler weeds should be cut into small pieces or crushed before being placed into the heap in order to ensure that they will regrow.

(ix) Household rubbish, especially from the kitchen, for example, outer coats of bananas, cassava, Irish potatoes, sweet potatoes, yams, etc.

(x) Food remnants.

(xi) Cut grass. The grass should not exceed 10% of the heap content. Although such grass is very useful, an excessive amount slows down the decomposition process. Even the allowable percentage must be thoroughly mixed with the rest of the refuse because grass by itself forms a slipping layer, thus slowing down decomposition.

(c) Preparation of refuse

Small refuse bits are decomposed by micro-organisms faster than big ones. Therefore, before forming the heap, all rubbish should be cut into smaller bits. It is also good to note that some items, such as bits of wood, stones, pieces of metal, glass, plastic parts of cups or plates, etc. will not decompose. Therefore, they must not be placed in the heap.

(d) Mixing the refuse

For one to get high quality compost manure, the refuse should be thoroughly mixed. There are two reasons for mixing the refuse.

(i) To provide the micro-organisms with whole meal (this type of mixture consists of one lot of refuse that contains very little nitrogen and another that has plenty of nitrogen, as well as refuse with adequate humidity and one that is dry).

(ii) It raises aeration channels (a thick heap of a single type of refuse like grass, leaves, saw dust, will in the end form a layer that is not penetrated by water, thus hindering the decomposition of the heap).

2. Agents of decomposition

The decomposition of a refuse heap is facilitated by micro-organisms i.e., bacteria and fungi. The others that help in the making of compost manure include:

(a) yeast
(b) actinomycetes
(c) protozoa
(d) snails
(e) earthworms
(f) algae
(g) beetles
(h) ants
(i) termites
(j) millipedes
(k) centipedes
(l) spiders

The creatures that participate in the making of compost manure can be classified into two groups.

(i) Those that are not visible to the naked eye except by use of a microscope. They are collectively called micro-organisms.

(ii) Those which are visible to the naked eye, for example earthworms.

Micro-organisms are responsible for the decomposition of the refuse.

After the micro-organisms have completed the process and the soil has begun to get settled, earthworms (and other similar creatures) set on their role. These creatures set up the refuse in the heap, thereby breaking it down into smaller bits. On the other hand, droppings from the worms help in nourishing bacteria in the heap and these play the actual role of decomposing the refuse.

For the worms to be able to live and reproduce, the heap should not be too high. A very high heap has high temperatures that may not augur well for the survival of the worms. The recommended height for the heap is 1.5 metres.

3. Temperature

The optimum temperature must prevail in the refuse heap if the micro-organisms are to effect the decomposition process. This temperature arises from the process of decomposition. The heap undergoes four stages:

(i) Tepidity

(ii) Rise of temperature to the highest level possible

(iii) Cooling down

(iv) Maturation of compost manure.

During the lukewarm stage (tepidity), compounds such as sugar, starch and fat are broken down. During peak temperature (60°C), weed seeds and the viruses in the refuse heap die. (The level of temperature in the heap is brought about by microorganisms.) As the heap cools down, hemicellulose and other similar compounds are decomposed especially by fungi.

By the time the compost manure is in the maturation stage, some of the compounds begin to destroy each other, giving way to the action of antibodies and, as already explained above, larger creatures of the earthworm type start their work. (The question of maturation will be explained in detail later.) However, the problem is often how to acquire optimum temperature in the heap, especially in small heaps that do not exceed one ton. In such cases, most of the heat escapes into the atmosphere. As a result, some parts in the middle of the heaps do not decompose. This means that the farmer has little chance of getting quality compost manure from smaller heaps. Therefore, farmers are advised to always aim at heaps that can generate temperatures of at least 60°C.

4. Air

The heap rots through the process of aerobic decomposition. An adequate amount of air is needed in various parts of the heap in order for the micro-organisms to get the oxygen required for breathing.

Air also helps in the expulsion of carbon dioxide from the heap. If air either lacks or is inadequate in the heap, anaerobic decomposition takes place. This occurs when:

(a) the heap has not been made properly;
(b) the heap has too much water;
(c) the heap gets inadequate oxygen.

Under these circumstances, certain micro-organisms affect decomposition with the following results.

(i) A distinctive, unpleasant odour at the site of the decomposing heap.

(ii) The manure takes longer than normal to get ready.

(iii) There is inadequate warmth in the heap. As a result, some weed seeds, certain viruses and refuse containing various diseases do not get destroyed and, therefore, the fertilizer will be of low quality. For this reason, it is important for the farmer to ensure that there is aerobic decomposition in order to get high quality compost manure.

Therefore, an adequate supply of air in the heap is of utmost importance in order for the micro-organisms to perform their functions well. On the other hand, too much air results in a quick loss of moisture amid heat in the heap. Therefore, there is need for moderate levels of air, neither too much nor too little.

There is also the need for the availability of adequate pores in the heap. Under normal circumstances, air will pass underneath the heap. However, it would be good to facilitate this entry. One way of doing this is to lay at the bottom, branches cut from trees, dry grass or dry leaves. The second method is by leveling up the soil at the place where the heap is to be constructed. In summary, the following techniques will enable the farmer to have adequate air in the heap:

· Laying dry grass leaves and/or branches of dry trees as the first layer at the base of the heap.

· Laying sticks in the middle of the heap at the time of construction and removing them when the work is complete. The passages left by the removed sticks will facilitate aeration in the heap.

· Having the proper heap size. If the heap is too small, it will not have adequate air. On the other hand, if the heap is too big, the micro-organisms will not function as effectively as required. This will result in very slow decomposition or none at all. The plant stems, branches, roots and even leaves to be used for the refuse heap should be 1 to 5 centimetres long.

5. Moisture

It is vital for moisture to be present in the heap for the sake of the living organisms existing there. The emphasis here is on moderate moisture. Too much of it will block air passages, resulting in the accumulation of bad smell from the heap. On the other hand, too little moisture renders the micro-organisms inactive. This is why it is imperative to cover heaps of compost manure in areas where there is plenty of rain, letting through only the required amount. Noteworthy also is the fact that rain water is very important in the preparation of compost manure as it contains some nutrients, such as sulphur.

The required amount of moisture in a heap is 50 to 60 per cent and efforts should be intensified to ensure an adequate amount at all times. The methods of doing so are as follows.

(a) Shielding the heap from wind by planting trees near the site of preparation of compost manure.

(b) Sprinkling the heap with a moderate amount of water frequently, especially during the construction of the heap, and proper mixing of the compost and water.

(c) In drought conditions or during the hot weather, the preparation of compost manure in pits (channels) is more convenient.

(d) Covering the heap with internal as well as external 'covers' as explained below.

6. Covers of the compost manure heap

The heap needs covers as a protection against spoilage of the manure. Too much rain on the heap causes loss of heat, over-saturation, closure of air passages and exhaustion of the plant nutrients. This results in low-quality manure that is not very useful on the farm. For this reason, the use of two types of covers is recommended.

(a) The inner cover

This is a bag that is placed directly on top of the heap and should have the following qualities.

(i) Enabling free flow of air in and out of the heap.

(ii) Resisting decomposition.

(iii) Should be made of hard and durable materials.

The reasons for using this type of cover are:

· It helps in preserving heat in the heap.

· It regulates the flow of air in the heap.

· It enables a certain amount of vapour coming from the heap to condense into water.

The above mentioned cover can be made from worm-out floor mats, gunny sacks, banana leaves or dry grass that has been stacked together in an orderly manner. This cover helps to prevent flies from settling directly on the heap. Hence, flies will not breed on the heap and be a nuisance to the farmer, neighbours or passers-by.

(b) The outer cover

This cover is constructed on top of the heap. It is usually in form of a raised platform, shed or anything similar that serves the purpose. The cover may be thatched with grass, covered in iron sheets, leaves or anything that is easily available to the farmer. It should be built in such a way that it will allow easy access to the heap. A slanted cover rather than a flat one, will enable rain water to flow to one side instead of stagnating on the roof.

7. The pH of the heap

This is a measure of the alkaline or acidic content of a substance. At the initial stages of decomposition, the refuse has some acid. However, after a few days, the acid decreases as the heap begins to get a moderate amount of alkali. The pH in the heap is important because too much alkali in the heap results in the loss of nitrogen which evaporates through the loss of ammonia gas. For this reason, it is not advisable to add lime to the heap.

On the other hand, if the refuse contains a high acid content, it may prevent the heap from having the required amount of luke-warmness, eventually preventing accumulation of heat in the heap thus hindering its decomposition. This is because some micro-organisms in the heap are killed by the presence of too much acid. While it is normal for some amounts of ammonia to be lost to the atmosphere, the loss can be greatly reduced if some soil is added into the heap. The amount of soil added should not exceed one percent of the total weight of the heap. The resultant compost fertilizer may be acidic or alkaline, depending on the type of refuse in the compost heap, its mixture, the amount of air available, moisture levels and the presence of lime. If the farmer raises the pH level of ash or lime in the heap, the level rises and expels the acid in the resultant compost manure.

8. Shuffling the compost manure heap

It is important to turn and thoroughly mix the heap in order to get high-quality compost manure. A week after the construction of the heap, the central part of the heap would have acquired the proper temperature levels, about 60°C. However, at the base of the heap, on the sides and towards the top parts, the temperatures would be low, resulting in the survival of seeds, weeds and viruses that cause certain diseases. For these to be destroyed, the farmer has to shuffle the heap so that the refuse at the bottom, on the sides and at the top of the heap also get to the centre of the heap for uniform decomposition at the required temperature rate. For this to take effect, it is necessary to observe the proper timing of shuffle intervals.

Usually, after the second shuffle, the decomposition would have fully taken place. Twenty-eight to forty-two days following the construction of the heap and its second shuffle, cooling takes place, and at this point the micro-organisms have accomplished their work and the weight of the heap has decreased by about half. Then follows the maturation of the compost manure, a stage that is reached during this final process in which particles of decomposed refuse slowly turn into humus, which we refer to as compost manure. This manure is now ready for application on the farms but must remain covered for protection against sun rays and too much rain when not in use. On the other hand, refuse that did not properly decompose is reused in the next decomposing heap. This is the one referred to as compost manure.

Before the fertilizer can be applied to the farm, the heap should be continually covered to protect it from the sun's rays and too much rain. Those bits that did not fully decompose may be decomposed in another heap.