Optimization of Water and N Regulation for Mung Bean (Vigna radiata L.) Cultivation Under Drip Irrigation Using TOPSIS Method in Mollisols Region of Northeast China

L.) production and the effective utilization of water and fertilizer resources is an important challenge for sustainable agricultural production. In this study, a field drip irrigation experiment was conducted on Mollisols in Northeast China, and twelve treatments were performed: four levels of soil water content (W1, 80~100% of field capacity; W2, 70~90% of field capacity; W3, 60~80% of field capacity; W4, rainfed condition) and three N application treatments (40 (N1), 80 (N2), and 120 (N3) kg/ha). We analyzed the coupling effects of water and N levels on mung bean growth, yield and yield components, water consumption, water use efficiency (WUE) and N partial factor productivity (PFP) in 2021 and 2022 and screened the optimal water and N regulation by the TOPSIS method. The results showed that the amount of N application dominated the regulation of water and N. In the first year, plant height, stem diameter, number of seeds per pod, 100-seeds weight, yield, aboveground dry matter accumulation, WUE, and PFP in mung bean decreased with increasing N applications at the same irrigation treatment. Furthermore, except for WUE, all results of the W3N1 treatment reached the highest levels, at 79.14 cm, 13 mm, 12.4, 6.2 g, 1430.45 kg/ha, 79.27 g (the drumming stage), and 35.76 kg/kg, respectively. The second year, plant height, stem diameter, yield and WUE had an increasing trend with increasing N applications at the W1. Based on the TOPSIS method, the W3N1 treatment could obtain the optimal comprehensive benefits of yield, WUE and PFP. This study can provide a most suitable water and N regulation model for guiding mung bean cultivation in the Mollisols region of Northeast China.