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Composting
Booklet. No. 64
Manuers & Fertilizers: MFS- 2/2
Contents
Preface
I. Introduction
II. Sources of Organic Wastes for Composting
III. Composting Principles of Composting
IV. Changes During Composting
V. Methods of Composting Application of Compost
VI. Manurial Value of Compost
Preface
One of the biggest problem fanners face is the maintenance of soil fertility. Continuous
application of chemical fertilizers is also harmful. Therefore, supplemental dose of organic
manures is essential to improve the soil fertility. Organic manures such as compost makes
better use of all farm and animal wastes and converts the nutrients in an easily available form,
thus adding to the soil fertility.
This booklet gives all the information necessary for compost making such as its
principle, source of materials used, economical and practical method of compost making which
is dealt elaborately along with its manurial value
K. T. Chandy, Agricultural & Environmental Education
I. Introduction
India has been known as an agricultural country and majority of its farming community
are small and marginal farmers. As the majority of farmers frequently lack in capital and due to
the high cost of chemical fertilizers, their use is limited for improving the productivity of their
land. Alternative source of nutrients thus, have to playa great role for the majority of the farming
community. The availability of fertilizers at the time when they are required is highly uncertain in
local places of our country. Erratic and uncertain rainfall makes the use of fertilizers highly risky.
Fertilizers also deteriorate the physical condition of the soil and exert a harmful effect on the
microbial population of the soil, if used continuously for a long time without any supplemental
dose of any organic manure. Therefore, we have to search for an effective alternative sources
of nutrient for increasing the production.
The practice of composting is an excellent method for improving the fertility of small
holdings of marginal and small farmers of the country. The practice of composting converts all
kinds of organic wastes into humus presenting an opportunity to the farmers to make better use
of wastes and refuse which are already present either at the farm or neighbourhood. All kinds of
organic materials that are usually considered as waste, and may be thrown away or burnt can
be used for composting.
II. Sources of Organic Wastes for Composting
Compost manures are the decayed refuse like leaves, twigs, roots, stubbles, bhusa,
crop residue and hedge clippings, street refuse collected from towns and villages, water
hyacinth and bagasse. The process of decomposition is hastened by adding nitrogenous
material like cow dung, night soil, urine or nitrogenous fertilizers. All th~se materials can be
obtained from various sources listed below.
1. Livestock and human wastes
Cattle shed wastes, cattle dung and urine, human excreta, by- products of slaughter
houses, animal carcasses, blood meat wastes, bones, horn and hooves, etc., from the livestock
and human wastes.
2. Crop residues, tree wastes and aquatic weeds
a. Crop wastes of cereals, pulses and oilseeds (wheat, paddy, jowar, bajra, gram, urad, mung,
cowpea, arhar, masoor, groundnut, linseed etc.).
b. Stalks of com, cotton, tobacco, sugarcane trash, leaves of cotton, jute, tapioca, arecanut, tree
leaves, water hyacinth, forest litter etc.
3. Green manures
Sunnhemp (Crotolaria juncea), dhaincha (Sesbania aculeata), cluster beans (Cyamposis
telragonoloba), senji (Melilotus parviflora), cowpea (Vigna caljang) horse gram
(Dolichosbiflorus), etc. are good examples of green manures.
4. Urban and rural wastes
Rural and urban solid wastes, household wastes, and liquid wastes like sewage and
sludge are a good source of manure.
5. Agro-industrial products
Oil cakes, paddy husk, bran, bagasse and pressmud, sawdust, fruit and vegetable
industry wastes, cotton, wool, silk wastes, tea and tobacco wastes etc. are the agro-industrial
products used for composting.
6. Marine wastes
Fish meals, seaweeds, tank silts (silt and clay deposited in tanks), ponds and reservoirs,
can also be used for composting. Million tonnes of organic wastes are annually produced in
India and major portion of it is wasted by not properly collecting and composting it. The average
production of wet dung per animal (cattle and buffalo) is around 1.1 kg per day. Taking cattle
and buffalo population alone which is around 240 million, nearly 2640 million kg of solid and
liquid excreta is produced. It is estimated that 15 million tonnes of compost can be obtained
from forest litter annually without adversely affecting the natural regeneration of the forest.
At the village level, frequently available organic wastes include dung, urine and stalks of
the crops, household garbage, cattle feed wastes, weeds, tree leaves and all the dead animal
remnants. If all these are collected and composted, they make a good manure.
III. Composting
Compost is a result of putting together (in a heap or a pit or a bin) all kinds of organic
materials to rot for a certain period. It is used as a fertilizer to provide nutrients to the soil and
improve their structure and fertility.
All organic materials require rotting before the nutrients can be released from them. In
compost, this rotting process has already taken place toa desired extent and the material has
turned into humus from which nutrients are gradually released. In non-composted material,
however, the rotting starts only after their application to the ground, so that the nutrients are not
directly available. The time it takes for releasing the nutrients depends upon the kind of material
used and the climate. Animal manure, young and soft plant materials can be spread directly on
field since it rots very easily, but the materials like straw twigs, wooden residues, mature grass
etc. are not rotten very easily. Moreover, it will have an adverse effect on the availability of the
nutrients. This is because of the absence of enough nitrogen in the material. Therefore, the
microbes responsible for the rotting of dead plants find no nitrogen from the added material,
rather they absorb the nitrogen from soil and the growing plants and the material will be left over
in the field. However, when these microbes die and their body rottens, nitrogen is again
released. The whole process may take two months or even more. Fixing of nitrogen with freshly
added residue is useful when there is no crop grown in the field. This fixation may avoid the loss
of nitrogen from the soil by leaching or volatilization.
IV. Principles of Composting
Composting is a process brought about by the micro-organisms. The enormous number
of micro-organisms such as bacteria, fungi, actinomycetes, and soil microfauna such as worms
in a moist. warm and aerated environment. attack the organic residues and produce humus.
The micro-organisms are the tiniest and simplest members of the plant and animal kingdom
which can be seen only through the microscope.
Micro-organisms increase in num ber to decompose the organic residues by multiplying
themselves. To increase their population, they require a large amount of carbon, nitrogen and
energy which they get from the residue itself. Oxygen and moisture, they obtain from the
surrounding atmosphere. Complex organic compounds of the residue are broken down into
carbon dioxide, water vapour and energy. Some portion of this energy is utilized by the micro-
organisms to carry out their own life processes, but a major portion of it is converted into heat,
which increases the temperature inside the compost pit or heap. Pit goes as high as 60- 70oC
which is sufficient enough to destroy many disease causing agents, harmful insects and weed
seeds. Carbon dioxide which is produced in a large amount leaves the pit along with some
vapour and consequentIy the volume of the heap or contents of the pit is reduced. Temperature
reduces again when the decomposition is over. The resistant part of the organic matter such as
humus, other broken-down products, and living and dead microbial cells are left in the pit as
final products of composting.
Some important conditions are prerequisites for obtaining a satisfactory compost
product. These conditions are discussed below.
A. The type of food
Generally, anything of plant or animal origin can be used for the compost pit or heap.
However, it is important to know the combination of materials that can be used. An important
aspect of this, is the amount of nitrogen compared to the amount of carbon or the ratio of carbon
to nitrogen (C:N ratio) in the material. The organic material can be grouped into two categories
on the basis of its nitrogen content. The organic matter with less nitrogen content has "hi:" C:N
ratio" and with more nitrogen has "low C:N ratio". First group consists of rough materials, which
do not decompose so readily but second group on the contrary, consist of dung, animal wastes
and young juicy plant parts which are decomposed easily. The list of the organic residues
coming under these two groups is given in Table 1. A compost pit should contain materials of
both groups in a certain proportion. If a heap consists of materials of high C:N ratio, the
decomposition process will be slowed down. On the other hand, if too much material from the
low C:N ratio group is used, huge loss of nutrient, especially nitrogen, will take place. The
balance between these two should be maintained.
Table 1: C:N ratio or different composting materials
Sl.No High C:N ratio Low C:N ratio
1 Straw Young plants
2 Twigs Animal manures
3 Mature grasses Slaughter house wastes
4 Old green leaves Dried blood
5 Pigeon pea stalks Fresh young grass
6 Millet stalks Bonemeal
7 Wheat straw Brewers waste
8 Coconut fibre waste Hoof and hornmeal
9 Rice straw Water hyacinth
10 Sugarcane trash Fish cleaning/meals, sea weeds
11 Rotted/fresh sawdust Kitchen scraps
12 Paper wastes Sour milk
13 Silk mill wastes
14 Peanut hulls
15 Mustard plants (after harvest)
16 Potato waste
B. Organisms
Numerous organisms take part in the decomposition of organic residues. Some micro-
organisms, help in the composting process by chewing, cutting and tearing the waste materials
into small pieces which are again more readily broken down by the micro-organisms. These
micro-organisms are bacteria, fungi and actinomycetes. The number of micro-organisms runs in
millions per gram of composting material undergoing decomposition. Micro-organism can
survive in a long range of temperature from 0 to 8O"C but, majority of them are active in
decomposition within the temperature range of30 to 40"C. In compost pit, however,
decomposition continues readily even at 60- 700C, indicating that some micro-organisms are
active even at a high temperature. A list of the organisms active in composting is shown under:
Table 2: Organisms in composting
Sl.No Group Organisms
1 Micro-flora Very small plants like bacteria,
actinomycetes, fungi, moulds,
yeasts, algae, viruses
2 Micro-fauna Very small animals like Protozoa
3 Macro-flora (larger Fungi (mushroom and
plants) toadstools)
4 Macro-fauna (small Mites, ants, termites, millipedes,
soil animals) centipedes, spiders, beetles and
worms.
C. Aeration
Adequate supply of oxygen is essential for the micro-organisms to carry out respiration.
Therefore, the heap should be prepared in such a way that it provides adequate aeration.
Anaerobic conditions (absence of air) leads to the development of different kinds of micro-
organisms, causing putrefaction of residue in which compounds of unpleasant smell are
produced.
In fact, both, aerobic and anaerobic decomposition takes place in the compost pit, which
is desirable for a good quality compost product. In the beginning, aerobic decomposition occurs
and the carbon dioxide liberated thereby depresses the effectiveness of oxygen. Anaerobic
condition is partially created and micro-organisms develop and carry out the anaerobic
decomposition. No special arrangements are required for anaerobic decomposition. However:,
the proper aeration of the pit is necessary.
Bulky organic residues should be chopped to the particles of 1-5 cm size or crushed,
before putting in the pit or heap. This ensures enough spacing between particles, where air can
circulate and it also provides greater area of residues for micro-organisms to act upon. Carefully
blending the materials and turning the materials 2-3 time during decomposition helps in the
supply of continuous and adequate aeration.
D. Moisture
Every living being requires water to sustain their life. Organisms engaged in composting,
too need sufficient moisture. The rate of decomposition slows down with a moisture content
below 40 per cent The optimum moisture content of 50 -60% should be maintained. But a little
higher level of moisture is desirable for the com posting of materials of fibrous tissues. For
practical purposes, the material should be as damp as a squeezed out sponge.
Special care is required to maintain an adequate moisture in the composting material in
tropical countries because of the dry materials available and rapid loss of moisture from the pit
or heap. This can be achieved by:
1. wetting the mixture initially and at each turning;
2. during monsoon, the heap may be built above ground at an elevated site as pit-composting
during hot weather reduces evaporation but increases water logging during monsoon;
3. making the heaps on the side of buildings or trees or the use of artificial wind breaks;
4. shading the heap from direct sunlight; and
5. building the heaps in such a way that the least surface area of the heap is directly hit by the
moving winds.
E. Temperature
Soon after putting the material in heap, rapid decomposition takes place. The heap
passes through all the stages of warming-up, high temperature, cooling down and maturing. in
the beginning, basic complex organic compounds like starch, sugars and fats are broken down
and the heat generated during this process warms up the heap soon after it reaches a peak of
60 to 70oC. At peak stage, loss of heat from the heap is more or less equal to the amount of
heat generated by the micro-organisms.
The peak period of heat in the heap is essential for the destruction of pathogenic
organisms and weed seeds. This generally occurs after 2-5 days of heaping or pitting. The
temperature in the middle of the pile goes upto 70 to 75oC and gradually cools down. However,
the optimum temperature is maintained at 60oC.
The temperature of the heaps containing residues of high C:N ratio like wheat straw,
paddy straw, jowar stalk, jamun leaves, etc. seldom goes beyond 52oC. This indicates that the
extent of rise of temperature in compost depends on the type of material being used and the
size of the heap. In the centre of large heaps, temperature goes too high. In the tropical
countries, size of the heap should be kept at 2.5 m wide and 1.5 m high in order to prevent
overheating and to ensure proper aeration.
F. Reaction or pH
The initial pH of compost heaps is slightly acidic i.e. around pH 6as is found in the cell
sap of most of the plants. The production of organic acids during the early stags of composting
causes further acidification (pH 4.5 -5.0) but, as the temperature rises, the pH increases to
slightly alkaline (pH 7.3-8.5) reaction.
Compost heaps are rarely too alkaline. However, in certain cases when composting is
highly alkaline, loss of nitrogen through volatilization takes place. Whereas, in highly acidic
conditions in the beginning, the heap fails to warm up. Generally, liming is not required to
amend acidity. Use of household ashes or egg-shell-shells will help to prevent too much acidity.
Ashes must be used if young and succulent materials are predominately used for composting.
Normal1y, If careful attention is paid to the making of the heap especially in moist area content
and aeration, acidity or alkalinity will not be a problem.
V. Changes During Composting
The plant and animal residues are essentially made up of sugars, starch, cel1ulose,
hemi-cel1ulose, lignins, resins, proteins, fats and waxes. When these waste materials are
placed in heap or pit for composting, they are attacked by a variety of micro-organisms
including bacteria, fungi, actinomycetes, protozoa, worms and insects larvae. As a result of
these activities, considerable portion of some of the constituent compounds in the residues are
degraded from their original complex forms to the new simple soluble forms. These simple
material may be solids or liquids like phosphate, potassium, ammonium, nitrate, organic acids,
etc. or gases like carbon dioxide, methane, hydrogen sulphide, hydrogen and ammonia. One
more important solid product formed during the course of decomposition is calIed humus which
is resistant to microbial attack and it forms major portion of organic residues. Among the organic
fractions, those which easily lend themselves to decomposition are the hemicellulose, proteins,
waxes and other nitrogenous substances.
VI. Methods of Composting
There has been revolution in the methods of composting evolved in the course of time.
The methods discussed below depict the chronological sequence as well as the technical
aspects of the composting.
A. Coimbatore method of composting
In the Coimbatore method of composting, the mode of decomposition is semi-aerobic.
Pits of 12' x 6' x 3' are dug and farm wastes are spread to a thickness of 2" over the cow dung,
and then bonemeal is sprinkled at the rate of I kg per layer. Similarly, the succeeding layers are
built till the whole mass rises above the ground level to a height of 2 feet. The mass is then
mud-plastered. In this condition, the decomposition is semi-aerobic for 4-6 weeks. After this
period the mud-plaster is removed and a turning is given to the entire mass and the
decomposition thereafter is fully aerobic. The compost manure is ready in 5 months. A heavy
loss of nitrogen and organic matter is often observed when ammonium sulphate, calcium nitrate
or Adco powder like strong starters are used. But when the slow starters like cow dung emulsion
and bone meal are used, the loss of nitrogen and organic matter are considerably reduced.
Thus, the superiority of the biological starter over the chemical starter under Indian conditions is
now well established.
B. Bangalore method of composting
In the Bangalore method of composting, residues are put in trenches. The length and
width of the trenches vary according to the amount of residue available. The depth of the
trenches is kept at 3 ft or less irrespective of their length or width. First, a layer of refuse about 6
inches in thickness is spread in the bottom of the trench and over this night soil to a thickness of
2 inches is spread. Normally the night soil does not require spreading and flows by itself, but in
case where it is hard it may be spread by long handled spades. Succeeding layers of refuse and
night soil are added till the heap rises above the ground level to a height of 1 foot Each layer of
night soil should be immediately covered with refuse and the top layer al the end of the day,
should be made 9 inches thick by using refuse. It is a good practice to cover the top of the heap
at the end of each day (whether the trenches are half or full) with a thin layer of earth, about 2
inches thick, since this effectively suppresses foul smell, conserves moisture better, avoids
nitrogen loss and minimizes fly nuisance.
In big towns, it is convenient to take up two or three trenches simultaneously for filling, to
cope up with the irregular arrival of carts of refuse and night soil.
If a proper proportion between refuse and night soil is maintained, then one's leg should
not sink while walking over the compost mass at the end of each day. If the leg sinks, it means
that excess of night soil is present and, hence, more refuse should be added. After filling about
20-30 trenches it would be found that the first trench has sunk to a depth of a foot or more
below ground level. Further such additions to the same trench may not be necessary at a later
stage, since sinking is slower after initial one month. In the rainy season, it is advisable lo make
the top of the heap dome-shaped so that rainwater is not allowed to be collected in the trench.
Bangalore method of composting is an excellent way of disposing the excreta produced
in the thickly populated cities. At the same time, it provides, compost which is richer than the
one produced by ordinary methods. This method is also called hot fermentation method in which
residues are made to decompose under anaerobic condition. This method of composting is
practised in the sub-urbs of many Indian cities.
C. Advanced method of composting
This method is an improvement upon the previous methods designed to encourage the
low scale composting which can be feasibly practised by the small farmers. The procedure
involved in this method is listed below.
1. Selection of site
While choosing the site for the compost pit the following points should be taken into
consideration.
a. The kind of materials to be used and from where these can be collected and transported.
b. The supply of animal refuse: whether animal manure is to be used or, sweeping of the animal
house is required.
c. The source of water supply.
d. Transport of the finished compost and the distance of the field in which compost has to be
applied.
It is important to locate the heap with the long side at right angles to the direction of the
prevailing wind and use the existing , wind breaks (building, trees) as shelter to prevent the
drying out of the heap. If the heap is placed in the shadow, it will be easier to preserve the
moisture. There should be enough place so that turning may be done conveniently.
2. The choice of structure
Mainly three structures namely pit, heap and bin are used for composting. In many
cases, any of these can be used. However, when the weather is dry, a pit is preferred to prevent
the drying of composting materials. The pits should not be deeper than 60 cm otherwise, their
aeration will be hampered. In humid regions, pit may be filled with water during rainy season,
therefore, a heap should be preferred. A heap shou1d not exceed 150 cm in height. Heap
should not be allowed to get too wet otherwise the nutrients are lost along with the leaking water
from the bottom of the pit. In too wet or too dry climate, heaps should be thatched.
3. Preparation of the material
Although many materials can be used directly, some may need pre-treatment before
adding to the heap, such as given below.
a. Too wet materials containing high moisture (eg. fresh green plants) should be allowed to
wither a little.
b. Rough and coarse materials such as stalks of maize, cotton, millets, etc. must be broken or
chopped before use. The ideal length is around 5 cm. The best way to break these materials is
to spread them over cattle shed. It will also help in collecting the urine and dung properly.
c. Woody materials such as sugarcane trash, tree bark and saw dust should be made moist
before being added to the heap or even-better is to soak them in water for several days.
4. Constructing the heap
All materials may be gathered at a time or may be stored until sufficient materials is
available to make one or several heaps. A common practice is to add the materials to the heap
one after another as they are available.
Normally, a heap is about 2 m wide and less than 1.5 m high, the length depends upon
the amount of material available. But it is better to build a small heap rapidly than a large heap
slowly. The minimum size advisable is about 1 cu m. Pits shou1d not be deeper than 60 cm.
Before siarting to build a heap, it is always good to begin by laying a lattice of old branches or
brush wood at the bottom, as this will provide aeration and prevent water logging. This should
be done in layers of different types of materials with a high C:N ratio. The layers should not be
too thick i.e., less than 10 cm for plant materials and less than 2 cm for manures. From time to
time, little soil should be added into the heap. Adding well rotten manure in the heap, in a little
amount is a very useful practice. Layers should be watered if material is very dry. Compact
materials like grass clippings and saw dust, should be pre-mixed along with a coarse ingredient
outside the heap. Regular addition of coarse materials like twigs promotes aeration. When the
heap is 150 cm high, ventilation holes should be made in the heap by pushing pointed wooden
poles vertically in to the heap about 1 m apart. When the heap is finished, it can be covered with
a layer of soil mud or straw. The next day the poles or stalks can be removed. Temperature will
begin to rise. After 4-5 days holes should be plastered to avoid the loss of heat and moisture.
5. Turning the heap
The heap is turned so that the material from the edges, where the temperature is lower,
is moved to the centre where it is warm, while centre of heap does not suffer from overheating.
All the materials in the heap should be exposed to the heat in order to kill germs, weed seeds,
insects and speed up the decomposition. Turning also improves aeration of the heap. Excess
carbon dioxide concentrated inside the heap is allowed to escape. Turning gives a chance to
check the moisture content of the material and if the material is too dry, it should be watered.
Some undecomposed patches can also be evenly mixed along with the material and good
quality compost is ensured.
The first turning should be done, after 2-3 weeks of heaping, when the temperature has
started to drop after reaching a peak. Materials are properly mixed, starting from one side of the
hear- ending towards another side. If necessary, sprinkle water. The heap can be turned again
three weeks after the first turning. Depending upon the warmth of the climate and kind of
residues, turning is done two to four times at an interval of about three weeks. If the heap is
prepared properly, not made compactly, holes are made and proper ratio of residues having
different C:N ratio is maintained, only one turning after 3-4 weeks of heaping is enough.
6. Maturing of compost
The time needed for the heap to mature and become a good compost, depends on the
local climatic conditions and the materials used. If the weather is warm, the heap is moist, well
aerated and good combination of materials is used for building the heap, the compost is ready
in three months time. In colder or dryer conditions and dominance of materials with high C:N
ratio, heap usually takes 6 months to ripe.
When the compost is mature or ripe, except for some small twigs, none of the original
components can be recognizable. The material is converted from dark brown to grey colour,
gives a earthy smell and is coarse. The volume of the mature heap is reduced to half of the
original.
D. NADEP method
The NADEP method of composting is the latest and widely acclaimed method. It has
been developed by Sri N.D. Panaripane at Dr Kumarappa Gowardhan Kendnl, Pusaad
(Maharashtta). The method has been proved to be highly economical and technically feasible at
the village level. This method involves following steps.
I. Construction of tank
In this method, a rectangular tank is constructed on the floor with the help of bricks and
puddled mud. The floor is made pucca by placing the bricks. The walls of the tank are 9 inches
thick. The inside measurements of the tank are kept as 10ft length and 6 ft width. The height of
the tank is kept at 3 ft and 3 inches. The tank of this size provides 200 cu ft area.
To ensure proper aeration inside the tank, two-brick-sized holes are provided in each
third row of bricks of the length-side-walls. In the width -side walls, one hole in each third row of
bricks is open. Care should be taken that the holes do not fall in the same vertical line. The tank
has the storage capacity of 3.5 tonnes and the economic life is expected to be 10 years. The
minimum of 10 tanks are desirable for economizing the production of compost
2. Materials required
Following materials are required to fill a tank:
a. Vegetative wastes, amounting to 1300 to 1400 kg. Polythenes, stones and glass pieces
should be sorted out from the material. "
b. About 100 kg of cattle dung is required. If bio-gas slurry is used then 200 kg. of material is
necessary.
c. Nearly 1000 to 2000 litres of water is required. In rainy season water requirement is less.
Depending on the requirement and availability of materials, ratio of the materials kept
can be altered. For example, to collect 100 tonnes material one can take 2.5 tonnes of dung,
47.5 tonnes of agro- wastes and 50 tonnes of waste clay.
3. Filling the tank
Follow the steps given below in sequence. Care should be taken that
the tank is filled within 48 hours of starting or the quality of product will deteriorate.
a. Spray cow dung slurry over the inner side of the wall of the tank..
b. Spread 6" thick layer of agro-waste. In this first layer, coarsest material available should be
spread. This will accommodate 100 to 110 kg of agro-waste.
c. Mix 4 kg of dung in l00-125 litres of water and spread it over agro-waste layer.
d. Spread 50 to 60 kg sieved, dry clay soil evenly over the layer. Sprinkle water over it.
All the subsequent layers should be laid in the same sequence. Avoid pressing the
layers too much. Fill the tank up to 1.5 ft above the mouth of pit. The top most layer of the tanks
assumes a shape of curve being highest in the centre. Generally, 11-121ayersareenough to fill
the tank to a required height Plaster the top of the tank using 400 -500 kg moist clay soil. This
forms approximately 3 inch thick layer of clay soil. If the clay layer cracks, fill the cracks with
dung paste.
After 15-20 days of filling the tank, contents are shrunk to about 8-9 inches below the
tank mouth. Again fill the tank by laying layers of residues in the same manner as described
before. Bring the height of the tank material up to the original level i.e. 1.5 ft above the mouth of
the tank. It takes 90-120 days from first filling for the material to compost adequately. Meantime,
light sprinkling of water from time to time and patching up of cracks if formed, should be done to
obtain a good quality compost Thatching the tank in too dry or too rainy weather is useful.
Check the pit material after 110 days of the first filling. Material will give an earthy smell. When it
is granular, dark grey in appearance, take out the pit material till the l20th day. If some
undecomposed residues are still left, sort them out and put them back in tank for further
composting.
The same pit can be used three times in a year. One tank at one time gives about 3.5
tonnes of compost. That is way one tank can produce 10.5 tonnes of compost in a year. The toil
in turning, as is needed in other methods, is also avoided in this method of composting.
E. Azo-composting
In this method of composting, bio-fertilizers are used to enrich the quality of manure.
While filling the pits with waste materials, bio-fertilizers are evenly spread over the layer of
waste materials., Rock phosphate is also used at the rate of 10 kg per tonne of raw material.
Two types of biofertilizers can be used in the pit viz, azatobactor and phosphobacterin.
Azatobactor biofertilizer contains free living nitrogen fixing bacteria. They fix atmospheric
nitrogen in to the manure. Phosphobacterin contains phosphorus solubilising bacteria which
convert the phosphorus of rock phosphate and organic materials into easily available forms of
phosphorus. The compost produced thereby is highly rich. Presence of rock phosphate, not only
gives increased percentage of phosphorus in compost but also prevents the loss of ammonia
from pit by absorbing it, thereby enriching the nitrogen content of compost.
VII. Application of Compost
Once the compost is mature in the pit, it can be applied directly to the field. If it has to be
stored, it should be protected from rain and sun either by a roof or by covering the heap with
coarse undecomposed material.
Keeping the compost in small heaps scattered over the field, is a common practice with
the farmers in India. This is a faulty practice as it permits the loss of nutrients by wind blowing
sunshine and rain. Therefore, it is recommended, that as soon as it arrives at the field, it should
be ploughed to a depth of about 10 cm so that nutrients released are available to the plant
roots. Further decomposition of compost takes place slowly in the soil releasing nitrogen,
phosphorus, potash and other micro-nutrients. Unavailability of compost is the main problem.
However, no excess amount of compost is harmful to the plants. For every hectare of land
where cereal crops are grown, 10-15 tonnes of compost is required per annum. It is difficult to
find enough material to prepare this much compost. Dressing of IS tonnes of compost per
hectare, once in every 2-3 years, helps in sustaining soil fertility. Where small amount of
compost is available, it is better to use it in small fields rather than in big areas. Those small
fields are preferred which support high quality crops, requiring high soil fertility.
VIII. Manurial Value of Compost
Compost serves as a good source of nutrients. On an average it contains 0.4 to 1.0%
nitrogen (N), 0.15 to 0.5 % phosphorus (P) and 0.2 to 0.7% potash (K). The contents of
nutrients are, however, very much dependent upon the kind of materials composted and the
method followed. The compost prepared by NADEP method is found to contain 1-15% N, 0.5-
0.9% P205 and 1.2 to 1.4 % K2O. The NADEP -compost is more or less 3 times richer than
farmyard manure.
A. Nutrient comparisons of compost with fertilizers
Tables 3,4 and 5 provide a comparison of chemical fertilizers providing NPK with
compost. These tables are based on following assumptions.
1. A typical farm compost in tropical conditions contains on a fresh weight basis: 0.5% nitrogen,
0.2% phosphorus and 0.3 % potash.
2. Such compost has moisture content of about 50% and FYM was used as activator.
3. Following percentage of the nutrients in fertilizers are I. available to the crop in the year of
application: nitrogen - 60%, phosphorus -40%, potassium -70 per cent.
4. The following percentages of nutrients in the compost become available to the crop in the
year of application: nitrogen - 25%, phosphorus -8% and potash -80 per cent
5. No account is taken of the availability in succeeding years. 6. To prepare and spread one
tonne of compost requires three man days.
Table 3 : Amount of nitrogenous fertilizers, supplying as ' much nitrogen as one tonne of
compost can (in the year of application)
Sl.No Fertilizer Percentage Amount (kg)
of nitrogen
(%)
1 Urea 46 4.5
2 Calcium nitrate 15 13.0
3 Potassium nitrate 13 16.0
4 Ammonium 25 8.3
chloride
5 Diammonium 18 11.5
phosphate
6 Ammonium nitrate 33 6.3
7 Calcium ammonium 26 8.0
nitrate
Table 4 : Amount of phosphatic fertilizers, supplying as much phosphorus as one tonne of
compost can (in the year of application)
Sl.No Fertilizers Amount of Amount (kg)
P2O5(%)
1 Single superphosphate 16 25.0
2 Triple superphosphate 42 9.5
3 Diammonium phosphate 46 8.7
4 Basic slag 10 40.0
5 Dicalcium phosphate 34 11.8
6 Bonemeal(raw) 25 16.0
7 Rock phosphate 30 13.3
Table 5 : Amount of potassic fertilizers, supplying as much potassium as one tonne of compost
can,(in the year of application)
Sl.No Fertilizers K2O Amount of (kg) Amount
1 Potassium sulphate 50 6.8
2 Potassium chloride 60 5.7
(muriate of potash)
B. Basics of calculations to compare nutrients
There are certain formulae which can be used to compare compost with inorganic
fertilizers, in terms of nutrient content:
Let Nc -be the percentage of nutrient present in the compost
Nf -be the percentage of nutrient present in the fertilizer.
A -be the percentage of nutrient available to the crop from
the compost, in a year.
B -be the percentage of nutrient available to the crop from
the fertilizer, in a year.
Then
1. a. Nc x 10 = weight of nutrient in kg in one tonne of compost.
Nc X A
b.---------- = weight of nutrient in kg in one tonne of compost
10 available to the crop in the year of application.
1000 x Nc x A
c. = ------------------- = weight in kg of inorganic fertilizer to supply an
Nf x B equivalent weight of nutrient to the crop as one
tonne of compost in the year of application.
3 X Nf
2. a. -------- = weight in kg of nutrient in 50 g of inorganic fertilizer,
10 which can be available to the crop.
Nf x B
b. ------------ = number of tonnes of compost providing
20 x Nc x A an equivalent weight of nutrient to the crop in
the year of application as 50 kg (a bag) of
inorganic fertilizer.
Example I: Find out the amount of urea supplying the same amount of nitrogen to a crop as one
tonne of compost in the year of application.
In the question:
Nf = 46%, No = 0.5%, A = 25%, B = 60%
Putting the values in the formula Ic,
1000 x Nc x A 1000 x 0.5 x 25 12500
--------------- = ------------------ = -------- = 452 kg urea
Nc x B 46 x 60 2760
Example 2 : Find out the weight in tonnes of compost supplying an equivalent weight of
potassium to crop in the year of application to a 50 kg dressing of muriate of potash.
In the question:
Nf = 60, Nc = 0.3, A = 80%, B = 70%,
From the formula 2b,
Nf x B 60 x 70 4200
------------- = --------------- = -------- = 8.75 tonnes of compost
20 x Nc x A 20 x 03 x 80 480
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