Effects of Conservation Tillage and Nitrogen Inhibitors on Yield and N2O Emissions for Spring Maize in Northeast China

Conservation tillage can improve soil health and carbon sequestration and is helpful for sustainable agricultural development. However, its effect on crop yields and nitrous oxide (N2O) emissions is still controversial. In this study, a two-year field experiment of spring maize was conducted from 2019 to 2020 in the Phaeozems region of Northeast China, involving two tillage practices (strip tillage and conventional tillage) and two nitrogen inhibitors (N-butylthiophosphorotriamine, NBPT and 3,4-Dimethylpyrazole phosphate, DMPP). The WHCNS (Soil Water Heat Carbon Nitrogen Simulator) model was calibrated and validated with field observations, and the effects of different tillage practices and nitrification inhibitors on spring maize yield, N2O emissions, water use efficiency (WUE), and nitrogen use efficiency (NUE) were simulated using the WHCNS model. Precipitation scenarios were set up to simulate and analyze the changes in patterns of crop yield and N2O emissions under long-term conservation tillage for 30 years (1991–2020). The results showed that concerning maize yield, under conservation tillage, the type of straw and nitrogen fertilizer inhibitor could explain 72.1% and 7.1%, respectively, of the total variance in maize yield, while precipitation explained only 14.1% of the total variance, with a 28.5% increase in crop yield in a humid year compared to a dry year. N2O emissions were principally influenced by precipitation, which could explain 46.4% of the total variance in N2O emissions. Furthermore, N2O emissions were 385% higher in humid years than in dry years. Straw under conservation tillage and inhibitor type explained 8.1% and 19.4% of the total variance in N2O emissions, respectively. Conservation tillage with nitrification inhibitors is recommended to increase crop yields, improve soil quality and reduce greenhouse gas emissions in the Phaeozems region of Northeast China, thus ensuring sustainable agricultural development in the region.