Intercropping maize with leguminous green manure can compensate for the losses in grain yield and N uptake caused by a reduced N supply

A critical challenge for global food security and sustainable agriculture is enhancing crop yields while reducing chemical N inputs. Improving N use efficiency in crops is essential for increasing agricultural productivity. The aim of this study was to evaluate the impacts of intercropping maize with leguminous green manure on grain yield and N utilization under reduced N-fertilization conditions. A field experiment with a split-plot design was conducted in northwestern China from 2018 to 2021. The main plots consisted of two cropping systems: maize–common vetch intercropping (IM) and sole maize (SM). The subplots had three N levels: zero N application (N0, 0 kg ha^–1), a 25% reduction from the traditional chemical N supply (N1, 270 kg ha^–1), and the traditional chemical N supply (N2, 360 kg ha^–1). The results showed that the negative effects of N reduction on maize grain yield and N uptake were compensated by intercropping leguminous green manure, and the improvements increased with cultivation years. The integrated system involving maize–leguminous green manure intercropping and a reduced N supply enhanced N translocation from maize vegetative organs to grains and increased the nitrate reductase and glutamine synthetase activities in maize leaves. The supercompensatory effect in maize leaves increased year by year, reaching values of 16.1, 21.3, and 25.5% in 2019, 2020, and 2021, respectively. These findings suggest that intercropping maize with leguminous green manure under reduced chemical N input can enhance N assimilation and uptake in maize. By using this strategy, chemical fertilizer is effectively replaced by leguminous green manure, thereby improving N use efficiency and maintaining stable yields in the maize-based intercropping system.