No-tillage with straw mulching increased maize yield and nitrogen fertilizer recovery rate in northeast China

Long-term intensive tillage has led to soil environment degradation, reduced fertility, difficulty in increasing maize yield, and low nitrogen (N) use efficiency in the Mollisol region of northeast China. In order to raise maize yield and improve the soil hydrothermal environment, we conducted field experiments to investigate the effects of different tillage practices and straw returning on the soil hydrothermal environment, maize yield, N fertilizer recovery and loss, aiming to increase both the maize yield and N fertilizer recovery rate. Four treatments were established: flat no-tillage with full straw mulching (NM), ridge no-tillage with full straw mulching (RM), rotary tillage with full straw incorporation (RR), and conventional tillage without straw (CK) as the control treatment. The two-year results indicate that both tillage practices and straw returning increased maize yield and the N-15 fertilizer recovery rate, accompanied by improvements in the soil water content (SWC) and regulation of soil temperature changes, as compared to the CK treatment. Specifically, the total N-15 fertilizer recovery rate of RM was significantly increased by 15.23% and 23.46%, while the N-15 fertilizer losses were notably reduced by 14.99% and 25.12%, respectively, compared to the NM and RR treatments. Additionally, the maize yield of RM was significantly increased by 3.10% in 2021 and 1.97% in 2022 compared to RR (P < 0.05), and it increased by 2.06% in 2021 and 0.91% in 2022 compared to NM (P > 0.05). The mean SWC of the 0-100-cm soil layer in RM significantly increased by 7.99% and 5.74% in 2021 and by 8.09%, and 5.50% in 2022 compared to NM and RR treatments during the maize growth seasons. At 60-80 days after sowing (DAS), when the air temperature was higher, the mean soil temperature of RM was significantly lower than that of the NM and RR treatments, by 0.46 degree celsius and 0.54 degree celsius in 2021 and by 0.31 degree celsius and 0.70 degree celsius in 2022. However, as the air temperature decreased at 100-140 DAS, the mean soil temperature in RM was significantly increased by 0.69 degree celsius and 0.81 degree celsius in 2021 and by 0.73 degree celsius and 0.94 degree celsius in 2022 compared to the NM and RR treatments. Our study indicates that RM treatment is the most suitable tillage practice and straw returning method in the Mollisol region of northeast China.