Mixed cropping of common vetch and hairy vetch enhances system productivity and economic returns in a wheat-based double-cropping system in an arid irrigated region

Context In arid irrigated regions with limited growing seasons, establishing sustainable post-wheat ( Triticum aestivum L.) cropping systems is crucial for agricultural intensification and soil conservation. Objective This study aimed to evaluate and identify an optimal post-wheat cropping system that enhances biomass production, soil quality, crop performance, and economic returns under arid conditions. Methods A seven-year field experiment (2018–2024) was conducted in northwestern China, comparing seven systems after spring wheat harvest: common vetch ( Vicia sativa L.)/hairy vetch ( Vicia villosa Roth.) mixture (W-CV×HV), common vetch/rapeseed ( Brassica napus L.) mixture (W-CV×R), hairy vetch/rapeseed mixture (W-HV×R), sole common vetch (W-SCV), sole hairy vetch (W-SHV), sole rapeseed (W-SR), and a fallow control (W-W). Results The W-CV×HV system demonstrated exceptional performance. It produced the highest biomass, with increases of 14.3–23.9 % over other mixtures, and enhanced crude protein yield by 13.7–44.4 %. This advantage was supported by strong interspecific facilitation (LER=1.18). This system significantly improved subsequent wheat performance, increasing grain yield by 2.7–8.8 % and yield stability by 66.9 % compared to sole legume cropping. After seven years, W-CV×HV most substantially improved soil quality, increasing soil organic matter and total nitrogen while reducing pH, EC, and bulk density. Economically, the system achieved 9.8–14.1 % higher monetary value than other cropping systems. Conclusion The legume-legume mixture of common vetch and hairy vetch represents a superior post-wheat cropping system, surpassing traditional fallow and single-species systems in agronomic, ecological, and economic performance. Implications This system provides a sustainable alternative for integrated agricultural intensification in arid environments, contributing to soil health stabilization, yield resilience, and improved farm profitability.