Effect of Tillage and Residue-Returning Mode on Soil Carbon Mineralizability and Accumulation in a Wheat-Maize System

Conservation tillage has been widely adopted to improve soil organic carbon (SOC) accumulation. To assess the effects of different tillage and residue-returning modes on SOC mineralizability and accumulation, a field experiment was conducted in 2015, including two tillage modes, i.e., no-tillage (NT) and rotary-tillage (RT), as well as three straw-returning modes, i.e., no straw returning (N0), wheat straw returning (WR), and wheat-maize straw retuning (WM). Wheat-maize root, maize straw, and wheat straw were added to soil samples during laboratory incubation. The results showed that NT significantly increased SOC concentration by 26.75% at a depth of 0-10 cm (p < 0.01). Although NT significantly decreased SOC mineralizability at soil depths of 0-10 cm and 10-20 cm (p < 0.05), the residue did not significantly affect SOC mineralizability in the 0-20 cm layer. The potentially mineralized C (C-p) and organic labile C fraction (C1) increased with the increase of residue amount. A significant correlation (R-2 = 0.662) was observed between C1 and SOC concentration. Notably, SOC concentration and mineralizability without straw returning were insignificant between N0 and WR in the 0-10 cm and 0-20 cm layers, respectively. This suggests that NT with WR is a promising strategy to increase SOC concentration and decrease mineralizability.

Automated summary

The effects of different tillage and residue-returning modes on soil organic carbon (SOC) accumulation were assessed in this study. The results showed that no-tillage significantly increased SOC concentration, and the combination of no-tillage and wheat straw returning helped increase SOC concentration and decrease mineralizability.