Optimization of tillage rotation and fertilization increased the soil organic carbon pool and crop yield in a semiarid region

Tillage and mineral fertilization are important strategies for maintaining crop production, but their effects on soil organic carbon (SOC) and labile fractions in semiarid regions are controversial. A 10-year field experiment was conducted to evaluate the effects of fertilization and tillage on SOC stock, labile fractions, soil quality and crop yields in a wheat-maize cropping system at the Loess Plateau. Results showed that balanced fertilization could provide comprehensive nutrition for crops and increase the crop residue input carbon, thereby increasing the SOC, readily oxidizable carbon, particulate organic carbon and dissolved organic carbon contents. In 0-50 cm layers, the SOC stock was increased by 3% under balanced fertilization compared to conventional fertilization. For tillage, no-tillage (zero tillage) and subsoiling rotation with less soil disturbance and higher stabilization rate of input carbon was the most effective tillage practice for increasing SOC stock. This tillage technique increased the labile carbon contents by 41%-63%, 5%-19% and 26%-67% compared to ploughing in 0-10 cm, 20-35 cm and 35-50 cm layers, respectively. Balanced fertilization combined with no-tillage and subsoiling rotation (BF + NS) increased carbon pool management index due to higher SOC and labile carbon contents, which contributed to the improvement of soil quality and the promotion of crop growth. Among all treatments, BF + NS treatment produced the highest SOC stock as well as wheat and maize yields. Therefore, BF + NS is the best strategy to increase SOC sequestration and to improve soil quality and productivity in semiarid regions.