Evaluation of press mud cake as a source of nitrogen and phosphorus for rice–wheat cropping system in the Indo-Gangetic plains of India

Press mud cake (PMC) is an important organic source available for land application in India. Adequate information regarding availability of nitrogen and phosphorous contained in PMC to rice–wheat (RW) cropping system is lacking. In field experiments conducted for 4 years to study the effect of PMC application to rice as N and P source in RW system, application of 60 kg N ha−1 along with PMC (5 t ha−1) produced grain yield of rice similar to that obtained with the 120 kg N ha− 1 in unamended plots. In the following wheat, the residual effects of PMC applied to preceding rice were equal to 40 kg N and 13 kg P ha−1. Immobilization of soil and fertilizer N immediately after the application of PMC was observed in laboratory incubation. The net amount of N mineralized from the PMC ranged from 16% at 30 days to 43% at 60 days after incubation. Available P content in the soil amended with PMC increased by about 60% over the unamended control within 10 days of its application. The P balance for the no-PMC treatment receiving recommended dose of 26 kg P ha−1 year−1 was −13.5 kg P ha−1 year−1. The P balance was positive (+42.3 to 53.5 kg P ha−1 year−1) when PMC was applied to rice. Application of PMC increased total N, organic carbon, and available P contents in the soil.