The field experiment was conducted on Lanzhou China to study the effects of applying forage rape planting density and nitrogen fertilizer on the topsoil(0~20 cm) soil granule composition

soil water-stable aggregates

soil micro-aggregates

soil clay dispersing rate and soil aggregation degree of wheat stubble multiple cropping rape.The results showed that soil water-stable aggregates and soil granule composition status of topsoil were improved after wheat stubble multiple cropping rape.Relative to the non-multiple rape cropland(CK) with multiple cropping rape topsoil soil

soil clay dispersing rate was dropped significantly or significantly positively

soil aggregates destruction rate(<0.001 mm) and compositional proportion of soil characteristic micro-aggregates(<0.01 mm/>0.01 mm) were reduced significantly

soil aggregation degree had a trend decreased in rape seedling stage and it was increased significantly or significantly positively in rape harvest stage

except for soil water-stable aggregates of rape harvest stage

soil aggregates percent content were all dropped no-significantly in analysis results of soil granule composition and soil water-stable aggregates and soil micro-aggregates

its mostly mechanism await farther study.Improving degree of soil water-stable aggregates was higher than soil micro-aggregates with multiple cropping rape.The percent content of soil water-stable aggregates and soil micro-aggregates and soil clay dispersing rate were all affected differently on topsoil

but the identity changed was lower and difference was not extra evidence in different rape planting density and N fertilizer treatment.The result of this study proved that wheat stubble multiple cropping rape had positive effects for improving farmland soil fertility.