Long-Term Effects of Fertilizers on the Soil Fertility and Productivity of a Rice–Wheat System |
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| Authors: | A Kumar & D S Yadav |
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| Institution: | Department of Agronomy, N. D. University of Agriculture and Technology, Kumarganj, Faizabad, U. P. 224 229, India |
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| Abstract: | Rice–wheat cropping system to which graded levels of NPK fertilizers had been applied for 20 years were compared for yield trends, and changes in response function, soil organic-C and available N, P, K and S status. This study of system in which only chemical fertilizers had been used over a long period enabled long-term yield declines of rice and wheat at different levels and combinations of NPK fertilizers to be evaluated. The highest rate of yield decline in both rice and wheat was found when 120 kg ha?1 N was applied alone. The lowest rate of decline was observed when all three nutrients (N, P and K) were applied, at 40, 35 and 33 kg ha?1 for N, P and K, respectively, followed by 120, 35 and 33 kg ha?1 (currently recommended levels). The yield response of rice and wheat to N fertilizer declined over the 20 years, with a higher rate of decline in wheat. In contrast, the response to applied P and K increased with time in both crops, with a higher response rate in wheat. With continuous application of N and P fertilizers, there was a marginal change in available N and K in the soil over time, but an approximately 3-fold increase in available P and an approximately 2-fold increase in available S were obtained by regular dressing of P fertilizer (SSP: 7 % P, 12 % S) over 20 years. The results revealed that balanced, high doses of NPK fertilizers are required to maintain soil fertility and raise grain yields. |
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| Keywords: | cropping system fertilizer rice–wheat soil fertility |
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