Effects of Nitrogen Supply on Dry Matter Accumulation, Water-Nitrogen Use Efficiency and Grain Yield of Soybean (Glycine max L.) under Different Mulching Methods

In dryland agriculture, mulching methods and nitrogen application have been extensively adopted to improve water and nitrogen use efficiency and increase crop yield. However, there has been a scarcity of research on the combined effects of mulching types and nitrogen application on the growth and yield of soybean (Glycine max L.). In the present study, four nitrogen levels (N0: 0 kg N ha(-1), N1: 60 kg N ha(-1), N2: 120 kg N ha(-1), N3: 180 kg N ha(-1)) and four mulching methods (NM: no mulching, SM: straw mulching, FM: film mulching, SFM: straw and film mulching) were set so as to evaluate the effects of mulching methods and nitrogen application on dry matter accumulation, grain yield, water-nitrogen use efficiency, and economic benefits of soybean in Northwest China from 2021 to 2022. The results show that the dry matter accumulation, yield formation, water and nitrogen use efficiency, and economic benefits of soybean were improved under different mulching methods (SM, FM, and SFM) and nitrogen applications (N1-N3), and that the effect is the best when the nitrogen application rate is N2 and the mulching method is FM. As such, a conclusion could be drawn that suitable nitrogen application (120 kg ha(-1)) combined with film mulching was beneficial for the utilization of rainwater resources and soybean production in the dryland of Northwest China.