Using Carbon Management Index to Assess the Impact of Compost Application on Changes in Soil Carbon after Ten Years of Rice–Wheat Cropping

Soil organic carbon (C) is a major determinant for the sustainability of agricultural systems. The changes in C pools (active or total) reflect the changes in an agricultural system. The C management index (CMI) can be used to monitor the soil over time, and it also tells whether a new system or practice is declining or rehabilitating the soil. Carbon management index was calculated for a long‐term experiment after 10 cycles of rice–wheat cropping to assess the influence of rice straw compost application either alone or in combination with inorganic fertilizers on soil C buildup. Total and labile C was greater in rice straw compost–amended soil as compared to unamended control or soils receiving inorganic fertilizers only. Application of rice straw compost increased the mean CMI (47.1) as compared to control (21.0). Labile C was positively related to mean weight diameter, and seemingly it plays an important role in the maintenance of physical fertility of soils and thus sustainability of the cropping system.