A manure is “a substance of designed to supply one or more of the essential constituents of plant food and, where necessary, to improve the physical condition of the soil to which it is applied”. The essential constituents of plant food must contain these elements—carbon, hydrogen, oxygen, phosphorus, sulphur, lime, magnesia, iron and probably silicon, chlorine, sodium, calcium, zinc and chloride, etc.
Of these carbon, hydrogen and oxygen and some of the nitrogen are derived from air and rain; most of the nitrogen, and the remaining elements being obtained from the soil. Almost every soil contains enough lime, magnesia, sulphur, iron, silicon, chlorine and sodium for the growth of a full crop but nitrogen, phosphorus and potash are often present but in small quantity and become exhausted by the removal of farm produce.
Hence, the addition of manure is indispensable to supply the deficiencies of these three constituents in the soil. But as some crops either contain excess of one or other of these, or are better able to obtain someone or other of them from the soil than are other crops, it is most economical to apply a special manure to meet the needs of such crops.
(a) Farmyard Manure:
Farmyard manure is the mixture of the liquid and solid excrements of farm animals with straw used as litter. It is the most important of all fertilizers as it is supposed to contain all the ingredients required for the growth of crops and also because it causes a certain amount of disintegration of the soil. In addition to its manurial properties, it has valuable physical effects upon the texture and water- holding powers of the soil and in dry seasons these may count for more than fertilizers towards ensuring good crops.
It restores humus in the soil, gives cohesion to the sandy soils, and renders clayey soils more porous and workable. It serves as a buffer in the soil ensuring even distribution of inorganic plant nutrients to the roots of crops. Besides, such manures result in steadiness in yield over a period of time, benefit to the succeeding crops by their residual effects and ability to withstand unfavourable weather conditions. It is, therefore, very essential when applying chemical fertilizers.
Average farmyard manure in India contains about 0.3 per cent nitrogen, 0.2 percent phosphoric acid and 0.30 per cent potash. On the other hand, manure with no fodder mixed with it contains from 0.5 to 1.5% of nitrogen, 0.4 to 0.8% phosphoric acid and 0.5 to 1.9% of potash.
It has been estimated that the cattle-shed manure supplies nearly ten times as much nitrogen and phosphoric acid to the soil as other manures and fertilizers put together and, this in spite of the fact that cattle-shed manure is now prepared in a most crude and primitive manner in our villages and only half of the cattledung is used for manure production.
About 200 million tonnes of dry cowdung having 15% of moisture, is being burnt yearly—the dry weight being equal to 170 million tonnes. The value of three plant nutrients alone lost by burning cowdung has been estimated to amount to Rs. 382 crores per year at an average value of Rs. 1,500 per tonne of nutrient. If cowdung were solely used as manure the net national annual drain on plant nutrients would be reduced by over 40 per cent.
Hence, every effort must be made to check the practice of burning cowdung as fuel. Sir John Russel has observed, “Wasteful practice making manure into cakes and burning it goes on unabated for the simple reason that no other equally useful fuel is available. The only way of stopping the practice, is to provide an alternative supply of fuel.”
The storage of farmyard manure presents considerable difficulties for when it is kept under the best conditions there will often be a loss of 15% of its nitrogen and it can be as much as 40% under ordinary methods of storage. Even under the covered-yard system, when the dung and litter are left under the animal until a layer several feet thick is produced and the product is protected from the weather as much as 15% of the valuable nitrogen is lost.
When the dung is carted out into a heap to ripen, the losses of nitrogen are even greater. The wastes of plant food provided by the animals is greatest in the case of nitrogen and potash and this is, in main, due to the defective methods of manure preparation adopted at present in the villages which do not utilise cattle urine as much as possible.
Russel and Richards after carrying out an elaborate investigation on the storage of farmyard manure at Rothamstead concluded that:
(1) The system of leaving the manure, in the box or covered-yard system, till it is required for the fields, is the best whenever this is practicable,
(2) The ideal method of storage is under the anaerobic additions at a temperature of 26° C,
(3) The manure heap, however, well made and projected, involved loss of nitrogen, and
(4) The best hope of improvement lies in storing the manure in watertight tanks or pits so made that they can be completely closed and thereby allow the attainment of perfect anaerobic conditions.
Therefore, what is needed is a continuous system of preparing farmyard manure in which:
(a) All losses of nitrogen are avoided, and
(b) The various steps from the raw material to the finished product follow a definite plan based on the orderly breaking down of materials and the preparation of finished product ready for immediate nitrification which can be easily incorporated in the soil.
It must be remembered that well-rotted dung is richer and more active than comparatively fresh undecomposed material, and hence, it is wasteful to turn heaps of manure to get the well-rotted material for top dressing. Directly the heap is broken it should be used.
In tracts of adequate rainfall and irrigated areas, the application of bulky organic manures will go a long way in maintaining and improving soil fertility. A basal dose of 10 tonnes of bulky organic manures per hectare in such tracts every year is needed. In the dry farming areas addition of 5 tonnes of bulky organic manures per hectare generally helps to increase the moisture conserving capacity of the soil.
The total requirement of such manures is about 1,150 m. tonnes. By 1965-66, the production of bulky organic manures was about 482 m. tonnes only: 1973-74 it was of the order of about 510 m. tonnes. In 1977-78 the total production was of 205 m. tonnes of rural compost and 6 m. tonnes of urban compost.
On an average, about 20 to 25% of nitrogenous requirements of the soil are being supplied from farmyard manure.
Farmyard manure can be applied to all crops grown in the rainy season or under irrigation. The quantity to be applied varies from 3 to 5 cartloads per acre in areas having less than 30″ of rainfall to 8 or 10 cartloads in areas of heavier rainfall….. For irrigated field crops the rate varies from 10 to 20 cartloads. Sugarcane, maize and garden crops, vegetables and fruits receive higher doses, amounting to 40 to 50 cartloads.
“The use of farmyard manure alone causes an imbalance in nutrition due to its relatively low content of phosphoric acid. Therefore, to keep the soil well supplied with all essential plant foods in a reality available form and also to keep them in good ‘heart’ bulky manures must be used in conjunction with superphosphate and other artificial fertilizers that contain the particular plant food or foods in which a soil may be deficient or which the crop to be grown may specifically require. The one will improve the physical condition of the soil and the other will supply the required quantities of plant food to produce a good crop.”
(b) Village and Town Refuse Compost:
Compost is another local manure which is made from a variety of refuse available both in the rural areas and the city. In rural areas usually all types of cattle and human wastes are made use of. Such manure is the rural compost. On the other hand, urban compost is made of municipal wastes and night soil. It is consumed within the city areas.
Under schemes for manure preparation in villages particularly in the Community Development Projects composting of farmyard manure and other wasteful material has become increasingly popular. The village compost scheme is working satisfactorily specially in the Punjab and U.P. The Punjab has adopted trenches 25 ft. in length, seven to eight feet in breadth and three feet in depth, whereas in U.P. the department has pits twelve and a half feet in length, eight feet in breadth and two to three feet in depth.
One trench of the U.P. dimensions would be necessary for a household. Some trenches, with pits smaller in length, can be located even in the congested areas. The trenches are filled up in breadth-wise sections with the material already used in the cattle-shed for absorbing cattle urine. In addition to dung-waste, litter and waste of horses and poultry combined with herbage, straw garbage, urine and other habitation waste such as household sweepings, wood-ash and leaves, etc., are also added.
No turnings are necessary, but when each section in four or five days reaches to a height of one and a half or two feet above the ground level the top is plastered over with a paste of cattle dung and earth (equal parts by weight) in order to conserve moisture and nitrogen and to prevent fly-breeding. The manure is then ready in four to six months’ time, and a rich product containing over two per cent nitrogen (on dry basis), obtained which would increase crop yields by 25 to 50%.
Besides rural composting, there exist vast resources of urban waste which are useful for growing vegetables and short duration crops.
These urban wastes are of two kinds:
(i) Solid wastes, which include city sweepings, garbage, kitchen wastes, slaughter-house waste, night soil and industrial organic wastes, and
(ii) Liquid wastes like sewage and sullage, comprising all waste and night soil.
The production of urban compost increased from 2.6 m. tonnes in 1961-62 to 3.4 m. tonnes in 1965-66. It was 3.6 tonnes in 1966-67; 4.1 m. tonnes in 1968-69; 4.2 m. tonnes in 1969-70; 4.3 m. tonnes in 1970-71; 4.4 m. tonnes in 1972-73; 4.6 m. tonnes in 1973-74; 4.8 m. tonnes in 1975-76; 5.4 m. tonnes in 1976-77 and 5.8 m. tonnes in 1977-78. During the Fifth Plan, 35 compost plants are to be set up.
The town compost contains, on an average 1.3% nitrogen, 1.1% phosphate acid and 1.5% of potash on dry basis.
The treatment of sewage results in production of sludge which is a valuable manure. It is estimated that about 2 lakh tonnes of sludge could be available per year by such treatment. As against the potential, the present availability of sludge is only 50,000 tonnes. The compositions of sludge is 30% nitrogen, 2.0% phosphoric acid and 0.5% potash.
The production of rural compost increased from 66 m. tonnes in 1955-56 to 115 m. tonnes in 1965-66. Its production was 144 m. tonnes in 1968-69, 145 m. tonnes in 1969-70, 155 m. tonnes in 1970-71, 170 m. tonnes in 1973-74; 184 m. tonnes in 1975-76; 200 m. tonnes in 1976-77 and 205 m. tonnes in 1977-78. The Fifth Plan target is 350 m. tonnes.
There are at present many bottlenecks which are hampering the intensification of compost preparation work in the urban centres:
(i) The arrangement made for the renewal of urban wastes by the municipalities or local bodies are inadequate. This factor hinders off-take of compost, which restricts further compost productions,
(ii) The poor financial position of the municipalities and local bodies,
(iii) Lack of special staff to organise compost work;
(iv) Delay in acquisition of lands for composting grounds; and
(v) Apathy and lack of interest on the part of sanitary inspectors in charge of compost work are important reasons for the slow progress in the urban composting programme.
Good quality manure can result by ensuring:
(i) Maximising collection of cowdung and urine fraction through the use of vegetable litter/earth;
(ii) Optimising carbon/nitrogen ratio by mixing the nitrogen rich materials with carbonaceous materials,
(iii) Preparing manure in a scientific way:
(a) In trenches of suitable size partitioned into sections;
(b) Avoiding leaching and seepage losses by making pucca trenches,
(c) Filling the trenches layer by layer,
(d) Ensuring optimum aeration, moisture, temperature and pH for proper decomposition;
(e) Adding sufficient quantity of superphosphate which not only controls nitrogen losses but also makes up the phosphorus deficiency in the final manure; and
(f) Covering the trenches so as to avoid volatalisation losses and percolation of rain water; and
(iv) Mixing the manure in the field by ploughing as soon as possible otherwise heaping it in open would lead to volatalisation losses.
While the potential capacity for composting of urban wastes is about 80 lakh tonnes, actual utilization at present is only 58 lakh tonnes. In addition to this, of the total availability of 700 m. gallons of sewage and sullage per day, only 200 m. gallons is being used. The remaining quantity is discharged into rivers and streams causing pollution of water detrimental to human health. This can be utilized in a number of urban areas.
The Committee on Natural Resources has shown that it is very necessary that adequate areas are earmarked for sewage farming in our growing towns which should not be built upon. Effective utilization of city wastes, including sewage and sullage, would mean not only increased agricultural production but also cleaner cities. Mechanical compost plants should be set up in selected cities to make organic manures from city waste.
The total quantity of sewage/sullage available in 80 cities and 600 towns is estimated to about 700 m. gallons per day, out of which about 240 m. gallons are being used at present for irrigation in about 145 cities and the area receiving irrigation is about 13,360 hectares. The discharge per day can irrigate about 2,10,000 acres. The extra produce in terms of food grains would be about 3 lakh tonnes, besides helping in the production of crops like plantains papaya; fodder crops, sugarcane, tobacco and cotton. The area under sewage irrigation in 1974-75 was about 24,000 hectares. This is to be doubled by 1978-79.
(c) Manures from Agricultural and Animal Wastes and Industrial Products:
Apart from the above major manurial resources, there are certain agricultural animal and industrial wastes which could be usefully utilised for providing manure to the soil.
Some of these wastes and products are:
(i) Rice bran, non- edible minor oilseeds, tobacco wastes and tobacco seeds, bagasse, marine algae, fruit and vegetable processing industry wastes, lac waste;
(ii) By-products from slaughter houses and dead animals, fishery wastes;
(iii) Blast furnace slag, by-products of coal carbonisation, salt, bitterns, coal ash and mica waste.
1. Animal Wastes from Slaughter Houses:
These are rich resources of nitrogen, phosphorus, calcium and other major and micro elements. The minimum annual mortality of large animals has been estimated at 8%. The consumable portion of animals present 30.50% of the total body weight, while the remaining portion consisting of blood, bones, liver, stomach, intestines, offal, hoof and hair forms waste material.
Keeping in view the large availability of organic wastes, the following groups of meal manures from the above animal wastes by chemical processing have been prepared:
(i) The Dried Blood:
The dried blood from slaughter house, contains 10 to 12% nitrogen. It may be used as a fertilizer by reducing it to fine powder form. This process consists in adding 1 to 3% of quicklime, which converts it into a solid cake which may be dried in the air without purifying and finally gives a fine and inodorous powder. Blood meal is now being used in Tamil Nadu, West Bengal, U.P., Maharashtra and Andhra Pradesh. Tea and coffee plantations use this manure.
(ii) Horn Turnings and Shavings:
These contain 10 to 15 per cent of nitrogen. So these may be used as manure but they are generally mixed with wood shavings and other sweepings of the workshops reducing its manurial value. Hoofs are, however, richer in nitrogen 11 to 15% than ground horn. Hair, wood, wool, wool rags, old felt, and feathers have the same value as horn. In the pure state, they contain 11 to 23 per cent of nitrogen. To serve as manure all those materials and particularly horn are reduced to a fine powder.
(iii) Bone-Meal:
Bones contain from 45 to 55% of phosphates chief as tricalcium phosphate and partly also in the form of magnesium phosphate. Bones containing 3.5 to 4.5 per cent of nitrogen, 3 per cent of calcium carbonate and 4 per cent of other ash (including silica) may be regarded as the light manure. Bone-meal as a manure is suitable for all types of soils particularly acidic soils where superphosphates cannot be used. It helps to increase the phosphorus content of grain and thus, enhance its nutritive value.
Bones of dead animals and bone-meal are little used in the country because of the ignorance and the age-long prejudice of the people, the absence of accurate information with regard to the use of the bones as manure in relation to different types of soil, and the difficulty of collecting and keeping the bones and of pounding them to power. At present about 40% of bones were being collected and it might be possible to increase the collection to 70 to 75% of the potential availability of about 36 lakh tonnes of bones. So far about 400 bone digesters and 120 crushing units had been set up.
The supply of bones can be increased with the adoption of these measures:
First, intensive salvaging of bones particularly from forests of U.P., Orissa and Assam should be undertaken since considerable quantity of bones of cattle and wild animals remain abandoned in these states.
Second, organised efforts should be made for the collection of bones at the village level. Such work can be advantageously organised by the existing machinery in the rural areas and rural flaying centres.
Third, all dead animals in the villages should be disposed of at a fixed place. Purchasing depots in the Block Development areas could perhaps be set up where the bones collected from the neighbourhood could be sold against cash at a reasonable rate.
(iv) Fish Manures:
The by-products of fishing are important sources of fish manure and guanos which are both nitrogenous and phosphoric in their constitution. Fish guano is simply dried fish. It contains about 1.5 per cent of nitrogen and 1 per cent of phosphoric acid. It has been used with success as a manure for root and cereal crops.
It is made on a considerable scale from various kinds of fish refuse like dried fish unfit for human consumption, fish guanos, the cake left after pressing the fish oil and pitted fish and often other refuse from fish- curing yards. In making guano generally oil fishes like cod, herrings, sprats, etc. are boiled and pressed for the sake of their oil and the residue is dried, powdered, and sold as fish guano. In India, out of a total of 32 lakh tonnes of fish production, only about 3 lakh tonnes are converted into manure.
Potentialities offer for further development of fish manure from spoiled fish, small shell fish, lobster, crab and inedible fish. This industry could be attached to fish processing plant like curing where guts and gills form the waste of materials, canning where tails, head and viscera are waste products and freezing. These materials roughly comprise 15-20% of fish weight. Fish meal contains 4 to 10% N, 3 to 9% P2 O2 and 1 to 2% K2O. It can be utilised for rice, coconut and many types of vegetables and fruit trees.
(v) Poultry Litter:
Poultry Litter is a rich organic manure since both liquid and solid wastes are excreted together running into as urine loss. It ferments very quickly and, hence, can be applied directly. About 40 adult birds produce nearly one tonne of manure a year.
2. Human Waste:
Human excreta or night-soil is another source of organic manure. Calculated at the rate of 1.8 kg. of nitrogen which night soil expelled from the body of one person on the average, produced in year, 55 crores of people produce 2.55 million tonnes of nitrogen; 1.1 m. tonne of phosphoric manure and 0.7 m. tonne of potash.
It has an approximate composition of 0.7% nitrogen, 0.3% phosphoric acid and 0.2% potash. But we are doing practically nothing to conserve and use this source of nitrogen supply due to prejudices. It can be easily used either in the form of poudrette or be converted into a form which is less obnoxious by the adoption of activated sludge process. This process reduces sewage, by the passage of air through it, a product which can either be used and required in the form of effluent from sewage tanks or dried and sent where there is a demand for it.
The activated sludge process is suitable only for towns which have a sewage system. It is much more expensive than conversion into poudrette but has the advantage of conserving a large percentage of nitrogen. The Planning Commission recommends to devise suitable latrines in rural areas so that excreta could be collected and used as manures.
The quantity of human excreta can be increased for use as manure by providing more conservancy arrangement in rural areas.
The main measures to be adopted are:
(a) Sense of conservation of human wastes among villagers through propaganda and education; and
(b) Incentives to panchayats to prepare and distribute maximum quantity of night soil compost of good quality.
3. Other Wastes:
(a) Oilseed Cakes:
Oil seeds and oil-cakes are another important source of manures, particularly the latter. If the cattle in India were fed with oilcakes, the manure would be returned to the soil, whose fertility might thus be conserved. Oilcakes are, generally, used as cattle food but some of them, for various reasons, are unsuitable for this purpose. These oil-cakes as well as damaged cakes are employed as fertilizers. They have been applied considerably in top manuring and for general use on light soils when a slower-acting fertilizer is prepared.
They usually contain 3% to well over 9% of nitrogen, 1.3% phosphoric acid, and 1.2% potash. The principal oil cakes used are groundnut, sesamum, neem, mahua, castor, rape, mustard, cottonseed, linseed and karanj. Neem cake is a valuable material to act as a nitrification retarder and slow release nitrogen fertilized for rice crop, to control root knot and also plant parasitic nematodes.
(b) Farm Weeds:
Many weeds are highly selective in the absorption of certain ions and are richer in major and minor elements. These nutrient-rich plant materials can be composed before flowering and used as manure.
(c) Water Hyacinth:
This is said to be twice as rich as town compost and four times as farm manure. It is suitable for jute and rice fields, vegetable gardening and fruit growing.
(d) Forest Litter:
About 15 million tonnes of litter can be composted without adversely affecting the natural regeneration of forests.
(e) Fruits and Vegetable Wastes:
Consisting of peels, stones, rags crown, skin, pomace and shell can be used to produce thousand tonnes of bulky manures.
(f) Others:
Other waste materials like coal and basic slag can also be used as manure. Besides supplying nutrients which they themselves contain, they help to fix atmospheric nitrogen and also release locked up phosphates of the soil.
4. Green Manuring:
When farmyard manure is scarce, green manure is a suitable form in which to supply organic matter to the soil to keep up the supply of the humus. Green manuring can be practised under irrigation and assured, rainfall condition where the moisture content in the soil is adequate and does not interfere with normal seasonal cropping.
In agriculture of most ancient civilizations like the Greek, Egyptian, Roman, Chinese and Indian, legumes have always formed an important part in the cropping system practised. The value of leguminous plants lies in their ability to fix the free nitrogen in atmosphere and accumulate it in their root nodules in appreciable quantities with the help of some useful microorganisms who live in symbiosis with the plants.
Various leguminous crops and nitrogen to the soil from 40 to 140 lbs. per acre, depending on the soil, climatic conditions and trends of crops, the average being 80 lbs. “Every crop or gram, peas, lytharus, sunnhemp, green gram, red gram, horse gram, pigeon pea and clovers, etc., leaves more than 20 lbs. of N (equivalent to two tonnes of farmyard manure or 100 lbs. of ammonium sulphate). About 40 to 50 lbs of N may be fixed by bean and clover crops”.
Taking of cereal and other non-leguminous crops continuously from the land exhausts the fertility of the soil, for such crops remove large quantities of nitrogen and other food elements without retaining any. Cereals have been rightly described by Shultz-Lapitz as “nitrogen consumer and leguminous crops as nitrogen accumulators”. Legumes, thus, are a very useful plant species which instead of depleting the soil help in increasing its nitrogen contents while deep-going and fine roots increase the organic matter content of the soil and, thus, improve its physical properties.
“The use of green manure increases the water-holding capacity of the sandy soil, improves the tilth of clayey soils by opening it, increases the accretion, facilitates drainage and requires less water for crops. It creates crumb structure in soil which is most important from agricultural point of view. It increases the organic matter content of the available nitrogen in the soil. It reduces the loss of mineral nitrogen by leaching, decreases the alkalinity of the alkaline soil and it may concentrate nutrients likely to be deficient in the surface soil and leave them there in the readily available form”.
“It also acts as catch crops, shade crops, cover crops and forage crops”.
The crops used for green manuring should possess these characteristics- rapid growth, succulence, abundant foliage and ability to grow well on poor soils.
The crops used for green manuring are of two types, viz, leguminous crops and non-leguminous crops. The former supply both nitrogen and organic matter, while the latter only organic matter.
The method of green manuring consists in growing such special crops which are more or less of a herbaceous character and rapid growth and capable of forming a good cover on the ground in a short space of time like senji, sebannia, beans, lentils, groundnuts, berseem, pulses, sunnhemp, guar, indigo, methra, soyabean, khesari, cow-pea or dhaincha either alone or intermixed with others for the purpose of digging or ploughing into the soil in a green state when they have reached a suitable height or before flowering.
This method of enriching the soil is considered to be one of the most economical as well as efficacious, fresh vegetable matter being returned to the soil with greater advantage than when it has been decomposed and much of its goodness has been lost in the progress of rooting and fermentation.
Of the shrubs (like Tephrosia Candida) and trees whose leaves are used for green leaf manuring. Honge, Cassia, Siamia, glyricidia, karanji and arak are the most popular.
Although rich in nitrogen, green manures also supply sufficient quantities of phosphoric acid and potash. Green manures and green leaves that contain the most nitrogen are- dhaincha, 3.5%, wild indigo leaves; 3.2%; and ferns 3.1%. Ranking lowest in nitrogen are- prickly pear 0.3% and miscellaneous weeds—0.8%. The plant containing the phosphate most is prickly pear with 1.2%.
Those with the least phosphate- wild indigo plant, — 0.2%, miscellaneous weeds and seaweeds, with 0.3% each. Ranking highest in potash are sea-weeds and ferns, each with 3.0%, and glyricidia, 9.8%. Plants containing the least potash are miscellaneous weeds 0.2%, forest leaves, 0.4% and wild indigo plant, 0.6%.
Data regarding green matter available from the various green manure plants are given below:
Experiments conducted with leguminous green manures indicate that 50 to 80% of the nitrogen is returned in the succeeding crop. Its residual effect lasts for 2 to 3 years but with decreasing efficiency. The nitrogen of a green manure is said to be much more readily available to the succeeding crop than that of stable manure. The rate of nitrification is greater in soils on which a leguminous crop has grown.
Increase in availability of other elements, improvement in physical structure of the soil, suppression of weeds, change in soil reaction, conservation of soil, and its nutrients, preservation of losses through leaching, etc., are other benefits accruing from green manuring.
It may be noted that areas receiving less than about 30 average rainfall are not suited for green manure crops unless irrigation facilities are available. Secondly, the value of crops following the green manuring crop must pay for the cost of the green manuring.
However, green manuring suffers from certain defects, e.g.:
(i) It cannot be used on the dry lands. A minimum of 75 cm. of rainfall or equivalent irrigation is basically needed.
(ii) In some cases green manuring has been found to be uneconomical. In fact, it has been done in the heavy deltaic paddy fields. In many cases, growing of green manure crops has restricted the growth of subsequent crops, and generally 2 to 3 years were needed for the land to be recovered.
(iii) In areas, where rainfall is high, i.e., from 200 cms to 255 cms, the growing of green manure crops has rather been found difficult.
In order to increase coverage under green manuring, it is necessary that a large number of demonstrations in the farmer’s field should be undertaken. Preparation of detailed plans for the production of required seed, devising methods such as peripheral planting, inter-cropping with green manures, protecting green manure crops against damage by cattle are other measures that may be taken up with profit.
The area under green manuring has increased from 8.4. m. hectares in 1968-69, to 8.5 m. hectares in 1969-70, to 10 m. hectares in 1970-71; 11.5 m. hectares in 1973-74. In 1977-78 it covered only 6 m. hectares.
5. Rotation of Crops:
This device is generally defined as “more or less regularly recurrent succession of different crops on the same piece of land”. Soil fertility can also be regained by practising the rotation of crops.
According to Leighty, “Crop rotation or the growing of different crops in recurring succession on the same land was recognised as advantageous by early agricultural scientists and was made the foundation of the improvement in agriculture which took place in England, in large parts of continental Europe, and in U.S.A. during the last part of the eighteenth and specially during the 19th century”.
The benefits to be derived from the growing of leguminous crops in alternation with cereals were distinctly recognised by the ancient Romans and Greeks as well as early Indians; and the benefits of growing inter-titled turnips or root crops in rotation with barley, clover and wheat were discovered about 1730 in England.
The farmers of ancient Rome understood that crops following beans, peas and vetches were usually better than those following wheat or barley, but it was not until the last quarter of the 19th century that people learned that, the legumes with the aid of associated bacteria have the power of feeding on the free nitrogen of the air while the non-leguminous plants can draw only on the nitrogen supply stored in the soil.
Experiments conducted at the Indian Agricultural Research Institute have shown that growing of a legume like berseem develops a stable type and high degree of soil fertility for the succeeding cereal crops and that higher yields of wheat could be obtained for 3 or 4 years than, when wheat is grown continuously.
The effects of crop rotation on yields are manifold:
(i) Rotation aids in controlling weeds and certain crop pests and diseases.
(ii) It may render manure and chemical fertilizers more effectively by increasing the soil supply of organic matter and different crops in themselves may exert beneficial effects on those which follow.
(iii) It reduces soil erosion and increases fertility by different crops growing in the same patch of land so as to enable intake of plant food from different layers of soil.
Study of the long continued soil fertility experiments made both in England and America has disclosed the following facts about crop rotation in its rotation to soil productivity:
(1) In general, crop rotation has been found to be practically 85% as effective as farmyard manure and complete commercial fertilizers in maintaining the yields of wheat, corn and oats and about 90% as effective as these fertilizers in increasing the yields of these major crops.
(2) The favourable effects of crop rotation do not impair the benefits derived from the use of fertilizers, so that when these two farm practices are combined the one practice adds to the benefits of the other.
(3) In comparison with the effectiveness of manures and commercial fertilizers, the relative value of crop rotation is practically 20% higher on soils sufficiently applied with lime as compared with soils that are acidic.
In view of these advantages offered by crop rotation, we must emphasise more on the system of practising crop rotation in India where farmyard manure is not available in full quantity as it is limited by the number of farm animals.
The table given above shows the rotation of crops followed in India.
6. Mixed Cropping:
Another way of regaining the lost fertility of the soils lies in the secret of mixed farming. Mixed cropping is the practice of sowing one main crop and one or two subsidiary crops together on the same land. The production of different crops in mixture depends upon the local soil and climate conditions. The system of mixed farming is practised widely in India and has been an important feature of all old agricultural civilizations.
The reason why Indian soils have not lost their fertility completely may in part be due to this system of mixed cropping leguminous component helping to maintain soil fertility. Crop mixtures such as wheat, gram, barley, peas, jowar, cotton, etc. are prevalent cropping systems in India. Such mixed crops, in addition to maintaining soil fertility are a guard against total failure of harvest due to unfavourable seasons, particularly some produce is obtained from the small holdings obtaining in India.
In mixed crops with different root habits the plant food is utilised to the best advantage and there is no competition. Mixtures also furnish protection to other crops, e.g., jowar protects cotton from hot winds in the Punjab. Besides maintaining the soil fertility, mixed cropping also enables the farmer to get not only in adequate supply of cattle-dung and urine but to grow food crops in proper combination with other products which enrich the soil.
The I.C.A.R. made successful experiments in U.P. and M.P. They showed that the yield was greater, money income increased substantially, and the cultivator had a better diet. Mixed cropping is specially suited for the dry farming areas where the main problem is to collect, preserve and use all the moisture available.
Sowing of a mixed crop is done by special seed drills. The mixed crop may be grown with three lines of main crop and one line of the alternate crop or five lines by one line.
The above table shows important crop mixtures followed in India.
Thus, it will be gathered that the important crop mixtures adopted in different parts of India are:
(a) Rice + cotton + red grams.
(b) Jowar + black gram + green gram + horse gram with groundnut or fibres like Hibiscus Cannabinus.
(c) Bajra + mesta + sunnhemp + groundnut + pulses.
(d) Ragi + niger + red gram + cow pea + jowar.
(e) Wheat + gram + sunflower + mustard.
(f) Cotton + groundnut + pulses.