LAUSR

Studying the dynamics of soil organic carbon (SOC) is important for understanding the mechanistic pathways of C stabilization into different SOC pools. An attempt was, therefore, made to assess the impact of double rice cropping system with different levels of fertilizers and in combination with organics on C sequestration and its stabilization in an Inceptisol using a 14-year old experiment at Jagtial under semi-arid climate in India. Total organic carbon (TOC) allocated into different pools in order of very labile > less labile > non labile > labile, constituting about 41.4, 20.6, 19.3 and 18.7%, respectively. In comparison with control, system receiving farmyard manure (FYM-10 Mg ha-1 season-1) alone showed greater C build up (40.5%) followed by 100% NPK+FYM (120:60:40 kg N,P,K ha-1+5 Mg FYM ha-1season-1)(16.2%). In fact, a net depletion of carbon stock was observed with 50% NPK (-1.2 Mg ha-1) and control (-1.8 Mg ha-1) treatments. Only 28.9% of C applied through FYM was stabilized as SOC. A minimal input of 2.34 Mg C ha-1 y-1 is needed to maintain SOC level. Treatments with organics showed a higher carbon management index, and microbial biomass and other labile pools of SOC. Results also indicated that100% NPK+FYM could maintain yield sustainability with a lower cost of carbon sequestration.