The total N application rates are 180 kg N ha-1 for RN and 240 kg N ha-1 for CN, respectively. MM: monoculture maize, IM: intercropped maize, MS: monoculture soybean, IS: intercropped soybean, IMS: maize-soybean relay intercropping; RN: reduced nitrogen, CN: conventional nitrogen. Data are mean±S.D., different lower case letters in the same column means significant differences between RN and CN. Values under ANOVA are the F-test, probabilities (P value) and coefficient of variation of the sources of variation (LSD, P < 0.05).