Effects of Different Soil Tillage Systems on Soil Carbon Management Index Under Double‐Cropping Rice Field in Southern China

Abstract

Core Ideas SOC and AOC were higher in CT and RT treatments than RTO at 0 to 5, 5 to 10, and 10 to 20 cm. Lability, LI, and CMI in the CT treatment were higher than NT treatment at 0 to 5 and 10 to 20 cm. SOC stocks were significantly higher in NT at 0 to 5 cm than under the RTO treatment. SOC stocks were significantly higher in CT and RT at 5 to 10 and 10 to 20 cm than under RTO. Interactions between tillage and soil organic carbon (SOC) impact soil structure, soil quality, and the calculated soil carbon management index (CMI). However, the effects of different tillage and residue management systems on the dynamics of SOC remain unclear under double‐cropping rice (Oryza sativa L.). Therefore, the effects of soil tillage and incorporated residues on soil bulk density, SOC, soil active organic carbon (AOC), and the CMI were studied in a southern China double‐cropped rice system. The experiment included four tillage treatments: conventional tillage with residue incorporation (CT), rotary tillage with residue incorporation (RT), no tillage with residue retention (NT), and rotary tillage with residue removed as a control (RTO). The results indicated that soil bulk density increased under NT in the 0‐ to 20‐cm layer, SOC was higher under NT than that of other treatments, and SOC in the 5‐ to 20‐cm layer was higher under CT and RT than under NT and RTO. The greatest SOC and AOC contents were observed under CT at the 5‐ to 10‐cm and 10‐ to 20‐cm layers. The CMI was used to assess the soil quality change with different soil tillage practices. The application of residue combined with conventional tillage or rotary tillage was more effective for increasing soil carbon pool index (CPI) and CMI than was rotary tillage with the residue was removed. The CMI for the 0‐ to 10‐cm depth under RT and CT were higher (P < 0.05) than the NT treatment. Meanwhile, RT significantly enhanced the SOC stocks over the RTO treatment at three different depths. As a result, based on soil CMI and C storage, double‐cropping rice using a no‐tillage system where crop residues are not removed could increase SOC in the surface 5 cm.