Impact of tillage, water and nutrient management practices on soil organic carbon pools in a seven-year rice-wheat rotation

At flowering stage of rice in 7th year of rice-wheat rotation, an increase in soil moisture had positive impact on Walkley-Black carbon (WBC) content of soil, while KMnO4-oxidizable carbon (KMOC) and microbial biomass carbon (MBC) were enhanced with increase in duration of drainage On an average, puddled soil showed 15.2% higher KMOC than non-puddled ones, whereas a reverse trend was observed in case of MBC. With reference to control (without any input), 69 and 103% increases in KMOC were recorded under recommended dose of NPK and 100% organics, respectively; corresponding values for MBC were 48 and 223%. Integrated use of mineral fertilizers with farmyard manure, green manure and crop residues enhanced the KMOC content by 99, 90 and 67% over the control, respectively; corresponding values for MBC were 143, 142 and 180%. Maximum improvement in carbon management index was observed in plots receiving 100% organic source of nutrients.