Impacts of conservation tillage on soil organic carbon and crop yield in black soil region of Northeast China: integrated regulation by climate, management and soil properties

Conservation management practices potentially enhance soil organic carbon (SOC) sequestration and restore soil fertility, thereby sustaining crop productivity and mitigating global warming. However, the magnitudes and controlling factors of the responses of SOC and crop yield to conservation tillage (no-till, NT; reduced tillage, RT) remain uncertain, especially in agricultural soils of Northeast China. Here, we conducted a meta-analysis of 527 observations from 140 publications to quantify the impacts of conservation tillage on SOC and crop yield, and identify key controlling factors across black soil region of Northeast China. Results revealed that conservation tillage significantly increased SOC by 4.17 % and crop yield by 2.69 % on average, with larger increases in SOC for NT (+5.92 %) compared to RT (+0.97 %), and the opposite trend for crop yield. Moreover, conservation tillage-induced SOC changes varied with soil depth, largely increasing in surface layers (<30 cm) but declining in subsoils (>30 cm). The variable responses of SOC and crop yield to conservation tillage were mainly affected by climatic conditions, management practices and soil properties, collectively explaining 68 % and 47 % of the variation, respectively. Specifically, conservation tillage achieved the most pronounced increases in both SOC and crop yield in soils with low initial SOC content and high silt + clay content, especially under mean annual temperature >8 °C and humidity index >0.45. Combining straw mulching and continuous cropping further amplified the benefits of conservation tillage. These positive effects peaked 10th year after implementation, and then gradually diminished, indicating the optimal duration of conservation tillage implementation for maximizing SOC sequestration and productivity. This study emphasizes that medium-term conservation tillage with straw mulching helps maximally enhance soil carbon sequestration and crop yield under warm-humid conditions in infertile black soils, offering a scientific basis for sustainable regional agriculture.