In-season temporal trends of carbon and nitrogen in rice (Oriza sativa L.) under long-term integrated nutrient management

Abstract

An investigation was undertaken to access the temporal trends of carbon and nitrogen during rice season under long-term integrated nutrient management (INM) on rice-wheat sequence (since 1999). The plant and soil samples were collected at 15 days interval from selected treatments (control, 100% N, 100% NP, 100% NPK and 100% NPK+FYM). These samples were analyzed for seasonal dynamics of soil organic carbon (SOC), water soluble carbon (WSC) and labile carbon (LC) pools, NH4 +-N and NO3-N and N uptake by rice. Soil organic carbon in all treatments started increasing after 3 weeks of sowing and it reached to the maximum at harvesting stage. Water soluble carbon and LC increased up to 5th week after sowing and it decreased afterwards in all
treatments. The values of SOC, WSC and LC were higher in NPK+FYM throughout the growing season of rice. A general decrease in NH4
+-N and NO3-N was observed in all treatments with progression of rice growth. Grain and straw yield of rice correlated significantly with SOC, WSC, LC, NH4
+-N and NO3 -N. Productivity of rice and nitrogen uptake increased under INM at all growth stages. Simultaneous inclusion of mineral nitrogen determined
at different stages contributed significantly towards both grain yield and nitrogen uptake in rice under ricewheat cropping system.