SOIL-FERTILITY AND FERTILISERS
Plant Nutrients and Soil Fertility
At least 16 elements, viz, carbon (C), Hydrogen (H), oxygen (O), nitrogen (N), phosphorus (P), sulphur (S), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), molybdenum (Mb), boron (B) and chlorine (CI), are essential for normal growth of green plants and hence also called Essential elements.
These are relatively bulky materials, such as animal or green manures, which are added mainly to improve the physical conditions of the soil, to replenish and keep up its humus status, to maintain the optimum conditions for the activities of soil micro-organisms and make good a small part of the plant nutrients removed by crops or otherwise lost through leaching and soil erosion.
Fig: ManureThey, thus, supply practically all the elements of fertility which crops require, though not in adequate proportions. Moreover, they are bulky with low nutrient with the high and rapid nutrient demand of HYV and hybrid crops.
It is the most valuable and commonly used organic manure in India. It consists of a mixture of cattle dung, the bedding used in the stable and any remnants of straw and plant stalks fed to cattle. The value of farmyard manure in soil improvement is due to its content of principal nutritive elements and its ability to
(i) Improve the soil tilth and aeration,
(ii) Increase the water-holding capacity of the soil, and
(iii) Stimulate the activity of micro-organisms that make the plant-food elements in the soil readily available to crops. The supply of organic matter, which is later converted into humus, is a property of farmyard manure.
Another method of augmenting the supplies of organic matter is the preparation of compost from farmhouse and cattle & shed wastes of all types. Composting is the process of decomposing vegetable and animal refuse (rural or urban) to a quickly utilizable condition for improving and maintaining soil fertility.
Fig: Composted manure
Good organic manure similar in appearance and fertilizing value to cattle manure can be produced by decomposing waste materials of various kinds, such as cereal straws, crop stubble, cotton stalks, groundnut husk, farm weeds and grasses, leaves, leaf-mould, house-refuse, wood ashes, litter, urine-soaked earth from cattle-sheds and other similar substances.
Green-manuring, wherever feasible, is the principal supplementary means of adding organic matter to the soil. It involves growing of a quick growing crop and ploughing it under to incorporate it into the soil. The green-manure crop supplies organic matter as well as additional nitrogen, particularly if it is a legume crop which has the ability to acquire nitrogen from the air with the help of its rot-nodule bacteria.
Fig: Green manureThe green-manure crops also exercise a protective action against erosion and leaching. The crops most commonly used for green-manuring in this country are sun hemp, dhaincha, cluster bean, senji, cowpea, horse gram, pillipesara, berseem or Egyptian clover and lentil.
Sewage and Sludge
The liquid waste, like sullage and sewage contain large quantities of plant nutrients and are used after preliminary treatment for growing sugarcane, vegetables and fodder crops near many large towns by operating sewage-farms. In many places, the undiluted sullage has been found to be too strong for healthy plant growth and if it contains readily oxidizable organic matter, its use actually reduces nitrates present in the soil.
Fig: Sewage and sludge
The disadvantages are still greater if sewage is used on land without preliminary treatment. The soil quickly becomes 'sewage sick' owing to the mechanical clogging by colloidal matter in the sewage and the development of anaerobic organisms which not only reduce the nitrates already present in the soil but also produce alkalinity. Bacterial contamination makes the eating of raw vegetables grown on untreated sewage or sullage a real danger to health. However, under no circumstances should any produce grown on a sewage farm be eaten uncooked.
Concentrated Organic Manures
Some of the concentrated materials such as oil-cakes, bone-meal, urine and blood are of organic origin.
Fertilisers are inorganic materials of a concentrated nature; they are applied mainly to increase the supply of one or more of the essential nutrients, e.g. nitrogen, phosphorus and potash. Fertilisers contain these elements in the form of soluble or readily available chemical compounds. In common parlance, the fertilisers are sometimes called 'chemical', 'artificial' of 'inorganic' manures.
Fig: FertilisersCompound Fertilisers
These fertilisers are multiple nutrient materials, supplying two or three plant nutrients simultaneously. When both nitrogen and phosphous are deficient in a soil, a compound fertiliser, e.g. ammophos, can be used. Its use does away with the necessity of purchasing two different fertilisers and mixing them in correct proportion before use.
Compound fertilisers contain plant food elements in fixed proportions and are, therefore, not always best adapted to different kinds of soils. Accordingly, the needs of different soils can generally be met most economically by the use of fertiliser mixtures containing two or more materials in suitable proportions. Mixtures usually meet nutrient deficiencies in a more balanced manner and require less labour to apply than straight fertilisers used separately. Mixtures containing all the three principal nutrients (N, P, and K) are termed completed fertilisers.
Fertiliser use in India
The use of chemical fertiliser plays an important role in boosting agricultural outpur. India soil though rich and varied is deficient in nitrogen and phosphorous which together with organic manure greatly influence the crop productivity. Our New Agricultural Strategy is based on increased use of chemical fertilisers since it is the only way to augment our foodgrain production which is essential for meeting the demand of our rising population.
There has been considerable increase in the domestic production of fertilisers over the years from 39,000 tonnes in 1951-52 to 13.9 million tonnes in 1995-96, but not enough to keep pace with the growth in consumption.
Since the adoption of the New Agricultural Strategy in the Sixties, the consumption of chemical fertilisers has been growing rapidly. The Government has been promoting the consumption of fertilisers through heavy subsidies. In spite of this, India's position is much behind other progressive countries.
The fertilizer consumption pattern in India, over the last three decades, reveals:
(i) Consumption of fertilisers in India per hectare was 75kg in 2015-2016. The corresponding figures for some developed countries were: South Korea (405 kg), Netherlands (315 kg), Belgium (275 kg), Japan (380 kg).
(ii) Adequate supply of water which is essential for the application of chemical fertilisers is lacking over large parts of the country and hence preventing their more rapid consumption in India.
(iii) The rainfed areas which constitute 70 percent of the cultivated areas consume only 20 percent of total fertilisers. The Government is taking steps to increase the consumption of fertilisers in these areas.
(iv) Rabi crop which accounts for 1/3rd of agricultural production, accounts for 2/3rd of fertilisers consumption. This is largely due to more assured availability of irrigation and subsoil moisture for rabi crops.
(v) There has been a steep rise in fertiliser subsidies which is a huge drain on resources and most important, the bulk of these subsidies goes to the more affluent farmers.
(vi) The sharp increase in international fertiliser prices has compelled the government to divert attention to greater use of organic manures, both farmyard manure and urban and rural compost.
The major constraints in fertiliser use in India are:
(i) High prices of fertilisers and shortage of capital.
(ii) Fear of heavy losses in case of failure of crops due to failure of rains.
(iii) Returns non-remunerative in case of inferior cereals.
(iv) Non-availability of fertilisers.
(v) Regional imbalances due to uneven spread of HYV seeds, variation in availability of irrigation facilities and infrastructural disparties.
Biofertilisers are natural fertilisers. They are the preparation of efficient of strains of micro-organisms capable of fixing atmospheric nitrogen into available form, solubilisng insoluble phosphate, producing growth promoting substances like vitamins and hormones and also play considerable role in decomposition of organic materials and enrichment of compost. Though biofertiliser cannot replace chemical fertiliser it can supplement it considerably.
Fig: Bio-fertiliserBiofertilisers include the following:
(i) Symbiotic nitrogen fixer e.g. Rhizobium spp.
(ii) Asymbiotic free nitrogen fixers eg. Azotobacter, Azospirillum etc.
(iii) Algae biofertilisers eg. blue green algae or BGA in association with Azolla.
(iv) Phosphate solubilising bacteria eg. Bacillus megatherium, Aspergillus awamori, Penicillum digitatum.
(v) Mycorrhizae (it is a symbiotic association of fungi with roots of plants);
(vi) Organic fertilisers (organic waste resources which include animal dung, urine, bone-meal, slaughter house wastes, crop residues, urban garbage, sewage/effluent etc.)
Rhizobium is useful for leguminous plants, Blue Green Algae for paddy and Azotobacter and Azospirillum for cereal crops. Biofertilisers enhance soil structure and texture, water holding capacity, supply of nutrients and proliferate beneficial micro-organisms. They are cheaper, pollution free and renewable.
Mechanisation of Agriculture
Meaning – Mechanisation of agriculture refers to extensive application of power driven machinery to agricultural operations starting from opening of land to sowing, harvesting, threshing winnowing and storage stage. The machinery used includes bulldozers, graders, tractors for ploughing, seed drills for sowing, cultivators, rollers, fertiliser distributors, combined harvesters for reaping and harvesting and other light farm machinery.
Need for Mechanisation
Mechanisation of agriculture is often associated with increase in agricultural production and reduction in costs. It is also useful in reclaiming barren lands. Thus the prosperity and richness of the peasantry in the western countries have been due, largely, to extensive use of farm machinery as agriculture there is commercialised and only a small proportion of the population is engaged in it.
Whereas in India the case is completely different because here agriculture is a way of life and a means of livelihood. Of the total work force in India, 67 percent are agricultural workers of which 31 percent are women. Therefore, in India some regard mechanisation of agriculture as desirable and necessary and other are against it.
For Mechanisation of India Agriculture
(i) Machinery increases speed of agricultural operations and thus saves time.
(ii) Machinery helps in performing heavy works like ploughing, land reclamation, carrying of earth, jungle clearance, drainage, cane crushing, oil extraction, thus reducing drudgery.
(iii) Reduces cost of production
(iv) Increase productivity of land and labour thus increasing total agricultural production to meet the demand.
(v) Increase income level of farmers.
Against Mechanisation of Indian Agriculture
(i) Mechanisation will aggravate the unemployment problem by creating surplus agriculture labour; but it can be more than offset by indirect increase in employment opportunities caused by the introduction of a machine.
(ii) Availability of adequate land is essential to adopt mechanisation, but in India majority of land holdings are small and scattered.
(iii) Widespread illiteracy, ignorance and poverty of farmers prevents them from adopting mechanisation on an extensive scale.
(iv) High fuel prices and shortage of mineral oil prevents Indians to use extensive oil based farm machinery.
(v) India does not have an adequate machine manufacturing capacity and there is a scarcity of mechanical skill. This argument is not sound. The domestic industrial capacity is gradually building up; the argument of non-availability of skill also does no seem to be true.
Farm mechanisation in India is inevitable for reclamation of land, conservation of forest land, ploughing of barren lands etc. Besides increasing the agricultural production and removing socio-economical disparity among the farmers. However, small size of the holdings and large surplus of labour in India call for limited or selective mechanisation (such as use of machines suitable for small farm and large cooperative farms) so that the labour displacement effects are minimised.
The policy of selective mechanisation has been great success in absolute terms especially in states of Punjab and Haryana, but does not compare well with advanced countries and with the size of Indian agricultural sector. Moreover, whatever mechanisation has taken place in Indian agriculture is largely confined to the richer farmers. The small farmers who constitute the overwhelming majority of Indian farming population remain by and large untouched by the process of mechanisation.
Agricultural Practices and Techniques
In order to increase the agricultural productivity and production to meet the ever increasing demand of agricultural products it is necessary, though difficult, to bring changes in traditional practices and techniques.
Traditional techniques are evolved over generations; they are continuously adjusted within rather restricted frame to changing circumstances. The farmers are reluctant to change to new modern techniques due to the following main reasons –
(i) The pursuit of traditional techniques involves less uncertainty, and
(ii) Since traditional techniques are passed on from one generation to the other, there is practically no material cost and relatively less uncertainty of output.
But a successful green revolution, as experienced in India cannot be achieved with the help of traditional agricultural techniques and practices. A change in them is almost essential. A number of agricultural techniques and practices have been evolved over the years. The more important amongst these are –
(i) Fallowing and crop rotation,
(ii) Double cropping,
(iii) Multiple cropping, and
(iv) Mixed cropping.
Fallowing and Crop Rotation
Fig: Mixed cropping
Fig: Double cropping
In regions of perennial water supply, even three crops are taken if resources permit. In double cropping., as in crop rotation, the aim is restoring soil fertility and hence the second crop is often one that fixes nitrogen, but the actual soil conditions decide the second crop.
With the introduction of short-duration varieties and water management practices, the trend is even towards growing more than two crops in a year, called multiple cropping. An American variety of short duration cotton, for example, can be grown in rotation with wheat. Similarly, short-duration varieties of wheat, rice, pulses, oilseeds, etc. have also been evolved.
Fig: Multiple cropping
A great many cropping sequences have been evolved from which the farmer can choose according to the marketability of the produced, profitability of the rotation, soil and climate conditions, and his input mobilising potential. It has been found that by introducing package measure the cultivation is able to resort to multiple cropping and at the same time harvest better yields. There is a scope for extending the multi-cropping practices to all areas where farmers have already been attuned to a higher level of technology through the HYVP.