Nutrient Management Strategies for the Next Decade Challenges Ahead

摘要

The mineral fertiliser has and will continue to play the key role in the augmentation of the food production in the entire world. In India the high yielding varieties of cereals ushered inthe 'Green Revolution'and the have worked as a catalyst in increasing the ferttliser demand. Of the three primary nutrients that the mineral fertilisers supply to the crop plants, nitrogen is the most deficient in Indian soils and it is also difficult to retain in soils due to various loss mechanisms,such as surface runoff, ammonia volatilization, leaching and denitrification. Furthermore, nitrogen is the key nutrient of proteins in foodgrains and is thus removed in the largest amount. This would explain why the nitrogen fertilisers are needed in the largest amount. As a contrast to N, plant requirements for P are much less and P is also well retained by the soil. Nevertheless, most Indian soils are either medium or low in available P and for good yields adequate P fertilisation is mush. As regards K, although it is taken up by the cereals in as large amounts as N or even more, a majority of Indian soils with the exception of Ultisols are able to supply a major part of K needs of crops. However,with the passage of time more and more soils are responding to K fertilisation. Adequate balanced fertilisation is tus the key. Of late, S has also been added to the list of major plant nutrients deficient in soils and deficiency of Zn is also beconing wide spread in India.Nutrient management is, therefore, becoming more and more involved. In the developed world, particularly in Europe,mineral fertiliser application went so high that it has shown its ill effects on the environment, particularly ground water pollution and eutrophication of surface waters. However, India is too far from such a situation. Neverthelesss,partly as a prophylactic measure and partly due to increasing demands of mineral fertiliser, an all out effort has to be made for utilisig crop residues, organic manures and biofertiliser to meet part of plant nutrient needs. This is referred to as integrated plant nutrient management (IPNM) or integrated plant nutrient supply system (SPNS)and is the key for sustained agricultural production.It is estimated that by 2010 about 246 tonnes of foodgrain will be needed annually and to produce this about 25+-2 million tonnes (mt) of plant nutrients (N+P_2O_5+K_2O)as mineral fertiliser would be needed. The major constraints in appllication of adequate amount of plant nutrients to crop plants and their efficient utilisation are lack of farm credit, non-availability of fertiliser application equipment,lack of precise fertiliser recommendtions, inadequate plant protection leading to crop damage and poor response, lack of crop insurance, particularly in dryland areas and a poor market infrastructure in several areas of the country. The research priorities and strategies include more reliable soil test for nitrogen, methods for utilising low grade rock phosphate, information on the concentration of plant nutrients that can be supplied through drip and sprinkler irrigation and frequency of such aplications particularly in orchards and vegetable crops where these irrigation techniques are being fast adopted. Also a farmer's participatory and awareness programme regariding the various nutrient loss mechanisms and the techniques that make fertiliser more efficient and the agriculture sustainable would be needed.