Contribution of organic matter,N and P through roots and stubbles in irrigated rice culture

Summary A study was conducted on the quantities of crop residues (stubbles) recycled into the soil after harvest with 2 early and 3 medium duration varieties of rice under irrigated culture. The addition of crop residues depended linearly on the total dry matter production of the plants. Dry matter (DM) of stubbles and the N content of the same showed a linear trend. The relationship between grain yield and N contribution through stubbles fitted to a linear regression. In early types the maximum N recycled is 16 kg/ha at an yield range of 4 to 6 t/ha while in medium types a maximum of 26 kg N/ha is recycled at the same yield level. The relationships between DM of stubbles and ‘P’ content of the stubbles and between grain yield and ‘P’ content of stubbles also turned out to be linear. The P content varied from 1 to 4 kg/ha in early types and 1 to 2 kg/ha in medium group. More N was recorded in the stubbles of the medium group while more P was found in the early duration varieties. There were clear varietal variations and the results were discussed in the light of the current literature.