Effect of Integrated Use of Fertilizer Nitrogen and Farmyard Manure or Green Manure on Transformation of N, K and S and Productivity of Rice-Wheat System on a Vertisol

The effect of long-term integrated use of FYM, green manure and fertilizer Non nutrient status of soil and productivity of rice-wheat system was studied in a field experiment conducted with various treatment combinations including FYM, green manure and fertilizer N. After 7 years of continuous cropping under various treatments, the differences in organic carbon, total hydrolyzable N, available and total S and K were significantly influenced. The organic matter and total hydrolyzable N status declined with application of fertilizer N alone and increased with conjunctive use of fertilizer N and organic manure. The continuous use of SSP increased the available and total S in all the treatments. Build-up in S status was mostly through organic S fraction. The use of FYM and green manure increased K availability in soil but a net negative balance in total K was noted irrespective of the treatment. The combined application of organic and inorganic N sustained the productivity, even at lower level of N application. The results indicated that without proper K fertilization, depletion of K may affect the sustainability of the rice-wheat system. Regression equations developed over the years revealed that incorporation of 5 t FYM/6 t GM saved 70–80 kg N ha⁻¹ y⁻¹ without any adverse effect on productivity of rice-wheat system and the soil health.