Intercropping alleviates the inhibitory effect of N fertilization on nodulation and symbiotic N2 fixation of faba bean

Symbiotic nitrogen fixation is commonly inhibited by N fertilization in intensive farming systems. We hypothesized that intercropping alleviates the inhibitory effect of N fertilization on nodulation and N2 fixation of legumes. Two years of field experiments (2006–2007) with different N-fertilizer rates (0, 75, 150, 225, 300 kg N ha−1) were carried out to test the hypothesis in a faba bean (Vicia faba L.)/maize (Zea mays L.) intercropping system in the north-western part of China. The results show that both the nodule biomass and nitrogen derived from the atmosphere (Ndfa) in intercropped faba bean were increased by 7–58% and 8–33% at the start of flowering, 8–72% and 54–61% at peak flowering, 4–73% and 18–50% at grain filling, and 7–62% and −7–72% at maturity, respectively, compared with sole faba bean. Intercropping with maize significantly alleviated the inhibitory effect of N fertilization on nodulation and N2 fixation, and improved the productivity of intercropping.