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Our main objective was to make rice-wheat system sustainable. We tried integrated approaches of fertilization, in-situ management of crop residues and green manures etc. My major thrust field is in-situ management of crop residues in intensive cropping system for soil and crop productivity improvement and their use as an integrated way of fertilization in rice based cropping systems. During the course of research studies, an idea of efficient utilisation of crop residues in intensive cropping system came to my mind and was tested for three years at research farm, Department of Soils, PAU, Ludhiana and during experimentation some fine refinements were made. Ultimately I have a sound technology which can be tried any where under similar agroclimatic conditions. More precisely, this technology is about growing four crops (Rice - Gobhi sarson (Brassica napus L. subsp oleiera var annua L.- Garden pea Pisum sativum- Mungbean(Vigna radiata) a year while managing in-situ residues of all crops of the cropping system. There are two similar situations in a sequence in this rotation i.e. legume crops follow non-legumes twice a year. Legumes following Non legume crops: According to this, the residue of legume crop, mungbean is incorporated fresh prior to the transplanting of rice which on decomposition rapidly releases N. The released N supplements 50-75% N requirement of the following rice crop. Similarly , fresh pea residue, of another legume crop reside, on incorporation releases N which is quickly taken up by the rowed Brassica napus crop especially when it is at an extensive vegetative growth and needs excessive available soil N Non legumes following legume crops: The other additive effects of residue incorporation in the this crop rotation are both cummulative and indirect. Incorporation of rice and Brassica ( low N containing residues) residues prior to planting of pea and mungbean crops, respectively, immobilizes soil mineral N temporarily and forces the legume crops compulsorily to grow in the absence of soil available-N. This enables legume crops to develop their inherent ability to grow and utilize elemental-N (N fixation), therefore exhaust little soil-N and spare N for the following crops. This immobilized and or conserved N, however becomes available with lapse of time and gets utilized by the following rice and brassica crops. ( Use of special agronomic manipulations have further improved this technology for applied fertilizer use, amelioration of adverse effects of applied residues on the following crop, efficient way of irrigation, integrated use of weedicides, ecological aspects etc. for better productivity) The periodic increments of addition of crop residues of different nature( fresh and dry) and properties(legume and non legume) almost after every third month makes the system to maintain organic carbon in soil even in sub humid tropics where the organic burns rapidly. Keeping a number of factors in view this system is considered as sustainable way of farming in sub-humid tropics. Besides this, efficient utilization of applied phosphatic fertilizer, integrated use of weedicides and insecticides have also been tried. This is an economical and sustainable approach of intensive cropping system. This approach, however, is suitable for irrigated plain areas. I tested this idea for its viability in field for three years and showed it to various experienced Extension Specialists, Agronomists, Weed Scientists, Physiologists, Crop Ecologists, Entomologists, Soil Physicist and Soil Scientists and all were of the view that this is a practical approach of sustainable farming. I also worked out the economics of this intensive cropping system which indicated that it is about 2.5 times better than the traditional rice-wheat system of the Indo-Gangetic plains of India. The similar principles could also be tried on other crop combinations. Aulakh, M.S., Tejinder Singh Khera and John W.Doran. 2000. Mineralization and denitrification in upland, nearly saturated and fooded subtropical soil. I Effect of nitrate and ammoniacal nitrogen Biol Fertil Soils 31 (2000) 2, 162-167 Aulakh, M.S., Tejinder Singh Khera and John W.Doran. 2000. Mineralization and denitrification in upland, nearly saturated and fooded subtropical soil. II Effect of organic manures varying in N content and C:N ratio Biol Fertil Soils 31 (2000) 2, 168-174
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