Abstract: Wheat and soybean intercropping is a high yield planting system widely distributed in one crop a year irrigation area of northwest China. Field plot and microplot root partition experiments show that under wheat/soybean intercropping, the land equivalent ratio was 1.23～1.26,and wheat was the dominant species with more competitive ability relative to soybean and possessing obvious edge row advantages, in which, 1/3 of the contribution came from its underground part. There was a recovery to soybean growth after wheat harvesting, which was considered as one of the mechanisms of interspecific facilitation. The harvesting index of intercropped species was significantly higher than that of sole species, indicating another mechanism of facilitation in the intercropping.

Key words: Wheat soybean intercropping, Interspecific competition, Interspecific facilitation