Integrated Effect of Mineral Fertilizers and Green Manure on Crop Yield and Nutrient Availability under Rice-Wheat Cropping System in Calciorthents

A field experiment conducted on Calciorthents revealed that average biomass production of green gram [Vigna radiata (L.) Wikzek] at initiation of flowering was 1.12 t ha−1 whereas residual yield of green gram was 1.20 t ha−1 after picking pods at full maturity stage. On an average, green gram yielded 0.55 t grain ha−1. The direct and residual effects of 75% NPK + green manure on grain yield of rice and wheat were more than those through addition of 100% NPK, which indicates that green manure could easily substitute 25% NPK to each of rice and wheat crop (equivalent to 25 kg N, 6.67 kg P and 8.3 kg K ha−1 in rice-wheat cropping system). Green manuring and green gram residue incorporation enhanced the uptake of N, P and K by rice and wheat. The direct and residual effect of green gram residues incorporation was inferior to green manuring because of high C/N ratio of the crop residue (34.3). Significant build up of organic carbon, available N, P and K in soils was recorded under graded levels of fertilizers and also with green manure and green gram straw incorporation after the picking of pods. This study suggests that a short duration pulse crop like green gram can give dual profit by way of providing grain for sale/consumption by the farmer's family and straw as the green manure.