Dependence of thermal and moisture sensitivity of soil organic carbon decomposition on manure composition in an Inceptisol under a five-year-old maize-wheat cropping system.

Abstract

Hydrothermal sensitivity of soil organic carbon decomposition in relation to global climatic changes is of great importance for C cycle in an agro‐ecosystem. To assess the sensitivities of SOC as affected by different organic sources and mineral fertilizer in Inceptisol, soil samples from a 5‐year‐old field experiment were collected from unfertilized control, 100% NPK, vermicompost, compost, and farmyard manure (FM) treated plots and analyzed for total organic C, labile C fractions and C mineralization kinetics by incubating soils at 25 and 35°C temperatures, and 0.33 and 1.0 bar soil moisture for 90 days. Compost and FM‐treated plots had ~23 and 22% higher total organic C than 100% NPK plots, respectively. Plots under vermicompost had similar C management index to FM but ~12% higher than compost. At 25°C temperature and 1.0 bar moisture, CO2 evolutions from vermicompost‐ and FM‐treated plots were ~29 and 11% higher than compost, respectively. Carbon decay rate was invariably higher in control and 100% NPK than organically amended plots. Temperature sensitivity of C was similar at 0.33 bar but different at 1.0 bar among the treatments. Moisture sensitivity of C in organic amended plots was similar at 35°C but different at 25°C, but their moisture sensitivity values were always higher than NPK. It could be concluded that manures with low C/N ratio and high N and P content would reduce C decay rate. Hence, to enhance C sequestration and reduce CO2 emissions in changing climatic situation, organic manure like vermicompost could be recommended.