5. Conclusions
The impacts of conservation tillage on crop yield and SOC concentration are affected by site environmental characteristics. In the cold area (MAT 0 - 3°C) of NEC, crop yield decreased under NT compared with CT, and in these environments, RT may be the better tillage practice. However, as temperature increases, crop yield increases compared to CT when using NT practices. ST was also observed to have a positive impact on yield when rotated with other conservation tillage measures, thus confirming that this practice can be safely implemented if it is necessary to loosen compacted layers. Conservation tillage measures had a significant impact on SOC sequestration rate and thus contributed to greater SOC concentrations, especially in a continuous cropping pattern under NT. Additionally, SOC effect under NT was significantly correlated with TN, C/N, and soil bulk density. Below a SOC concentration of 20 g kg-1, maize yield was found to increase linearly as SOC increased under NT, and magnitude of the yield increases under ST tended to be larger the longer ST had been in operation.
Overall, our data suggest that the appropriate use of different conservation tillage measures in different area in NEC could result in the win-win situation of crop yield increase and carbon sequestration, and will help protect soils from degradation and stabilize crop yield in NEC.