Long-term influence of organic and inorganic fertilization on soil fertility and productivity of soybean–Wheat system in a vertisol

The status of soil nutrients, their depletion and build-up and crop productivity after a twentyeight years (1972–2000) of intensive cropping under various fertilizer and manurial treatments on Typic Haplusterts was studied. The rotation was soybean-wheat and treatments included various combinations of N, P, K, Zn and FYM. After twenty-eight years of continuous intensive cropping under various fertilizer and manurial treatments, the differences in the values of organic carbon, available N, P, K and S in soil at 0.15 m depth and crop productivity were found to be very marked. The data on yield show that theapplication of recommended dose of N, P and K with manure @ 15 t ha⁻¹ helped in sustaining the yields of soybean and wheat over the years. The inclusion of FYM in the treatment schedule improved the organic carbon status and available N, P, K and S in soil thereby, sustaining the soil health. The omission of S in the fertilizer schedule has caused a continuous depletion in the available-S status of soil. The status of available K in soil was found to decrease in all the treatments but the decrease was of lower magnitude in 100% NPK+FYM and 150% NPK treatments indicating the need to raise the level of K fertilizer application to meet the demand of the crops.