nutrient management in soils for improving crop productivity
Modern agriculture largely depends on the use of high cost inputs such as chemical fertilizers, pesticides, herbicides, improved seeds, assured irrigation, scientific management and labour saving but energy intensive farm machinery. The application of such high input technologies increased the production but there is growing concern over the adverse effects of the use of chemicals and soil productivity and environment quality. When population pressure was low, mono-cropping was a rule, with the increase in population various multiple cropping system have become popular.
Similarly, from the use of single nutrient, application of multi-nutrient has adopted. Because no single source of nutrient can satisfy the need of all the essential elements that crop needs for growth and development. Nutrient management in multiple cropping system is more efficient than in individual crop because there is a residual effect of nutrients for e.g. phosphatic fertilizer and organic sources of plant nutrients.
To sustain the productivity of different crops and cropping systems, efficient nutrient management is vital. There is a need to develop more efficient, economic and integrated system of nutrient management for realizing high crop productivity without diminishing soil fertility.
A two-fold strategy may be useful in nutrient management. First, to continue to encourage the use of fertilizer for a faster growth in agriculture and second, to popularize the use of recycled crop residues, green manures, use of compost (both urban and rural) and biofertilizers as a supplementary source of nutrients, in conjunction with chemical form of plant nutrients. There is need to add plant nutrients to the soil on the basis of soil fertility states. The application of nutrients according to soil-test-based-fertility-assessment ensures better efficiency and improved profitability. Principle: (a) basic soil fertility and climate. (b) nature of crop in cropping system. (c) atleast 30% of the total nutrient levels NPK in organic form.
Organic vs inorganic
Organic sources of nutrients are supplementary to chemical fertilizers and use of biofertilizers considered as environment friendly, in terms of protecting the quality of underground waters, soil property and environment in general. Complete depends on organic sources can sustained a yield target equivalent to that prevailed during pre green revolution era. It would be able to meet only 1/3 of the nutrient requires for the present level of foodgrain production, if the whole of organic resources utilised available for agricultural use.
These are low agricultural input environments friendly used as seed inoculation and also soil inoculation. Inoculation of Rhizobium. Azotobactor and Azospirillum substitute, 19,22 and 20 kg N/ha, respectively. Blue green algae (BGA) applied @ 10 kg/ha gave a saving of 20-30 kg N/ha and Azolla @ 6-12 t/ha had an N equivalent of 3-4 kg/t.
The potential of rural and urban compost in India is estimated to be 800 and 16 mt respectively. Less than 50% of the manurial potential of the livestock population is utilised at present in crop production. The major contributor of rural compost is animal dung, which has a potential are about 7 mt of NPK. Night soil if properly exploited can provide about 5 mt of NPK nutrients. About 1/3 of the residue potential is available for utilization in agricultural production about 400 mt of crop residues are produced in the country which have potential of supplying about 7.3 mt of NPK.
The practice of green manuring for improving soil fertility and supplying apart of nutrient requirement of crop is aged old. Depending on the crop grown the N contribution by green manure crops varies from 60-280 kg/ha. Leguminous green manures can fix large quantity of atmospheric N2 which generally can accumulate about 100 kg N ha-1 in 50-55 days but can reach up to more than 200 kg N ha. The problem with green manure crops is that they compete with cash crops for space, time, water and other inputs.
To assess on farm and off-farm resource availability through survey related to soil and nutrient management.
Fixing yield target depending on the resource availability.
Soil test based estimation of nutrient requirement with due consideration on soil amendments.
Integration of all nutrient resources available for a given circumstances.
To determine time, method, mode of application considering the type of crops involved in the cropping system.
To adopt efficient soil and water conservation measures to check soil erosion, soil organic C & nutrient losses.
Maintaining soil fertility in terms of soil physical, chemical and biological properties and processes.
The average size of an operational holding is 1.57 ha. small farm size has major implications for fertilizer and water management practices.
In India there are 519 soil testing laboratories. The total analysing capacity of these laboratories is about 6.5 million samples per annum. In order to provide soil test-based fertilizer recommendations the existing analysing capacity of the soil testing laboratories needs to be augmented almost 15-20 times.
Soil fertility will only be maintained and enhanced by the actions of farmers. Farmers knowledge is essentially local, based on observation and experience within specific farming systems and agro-ecological contexts. Hence farmers participation is important.
The annual potential of organic resources ranges between 10.5-16.2 mt of NPK, only around
3.9-5.7 mt of plant nutrients can be made available for agricultural use. Average organic manure use at present is about 2 tonnes ha-1. The coverage under green manure crop is about 6 m ha and the use of bio-fertiliser, against a total bio-fertiliser demand of 1 mt, the current supply is less than 10,000 tonnes. Only 25% nutrient needs of Indian agriculture can be met by utilising various organic resources namely FYM (200 mt), crop residue (30 mt), urban/rural wastes (10 mt) and green manuring (25 m ha).
For its mobilisation, processing and application, because of low nutrient content and bulkiness it requires high labour.
Greater awareness needs to be created among the farmers for the use of farm resources on generation and its proper recycled and encouragement for the production of compost and green manuring.
The major components of the system needs attention are: recycling of solid wastes and crop residues by composting and vermi composting, more popularisation of janata bio-gas plants, encouraging growth of legumes as part of the crop rotation for grain and fodder purposes, using sewage sludge and effluents for agriculture, integration of green manures, green leaf manures. BGA and azolla in rice culture.
Popularising bio-fertilizers to augment N and P supply by improving/strengthening transportation, distribution and storage infrastructure. Also enhancement of shelf life of
bio-fertilizers, development of new strains and easy technique for viability test for bio-fertilizers.
It needs to be refined so as to reduced the time, manpower and cost of chemicals during estimation and soil test laboratories should be strengthened and up graded for soil and plant analysis, promoting balanced use of chemical fertilizers on soil testing and correction of secondary and micro nutrients deficiencies in soils.
Advantages of introduction of green legumes in the cropping systems should be promoted. Use of phospho-compost should be promoted to supplement phosphatic fertiliser to a great extent. Research on incorporation N fixing ability in non-legumes need to be accelerated.
Promotion of appropriate soil, water and nutrient management and other agronomic practices to maximize nutrient use efficiently and economically.