麦茬复种饲料油菜对耕层土壤团聚体的影响

通过田间小区试验，研究了不同油菜种植密度与施氮肥对麦茬复种饲料油菜耕层（0～20cm）土壤颗粒组成、水稳性团聚体、微团聚体、粘粒分散率和团聚度的影响。试验结果表明，麦茬复种油菜能提高耕层土壤水稳性团聚体，改善土壤颗粒组成状况；与对照（CK）相比，耕层土壤粘粒分散率呈显著或极显著性降低，〈0．001mm的土壤团聚体破坏率和特征微团聚体比例（〈0．01mm／〉0．01mm）显著降低，而土壤团聚度在油菜苗期为降低趋势，收获期呈显著或极显著性增加，〉0．25mm的土壤团聚体百分含量除收获期的水稳性团聚体外均呈不显著性降低。复种油菜对土壤水稳性团聚体改善贡献高于土壤微团聚体。种植密度和施肥处理均能不同程度地影响和改变耕层土壤水稳性团聚体、微团聚体和粘粒分散率的含量，处理间规律性不强，差异性并不十分显著。说明麦茬复种饲料油菜对农田土壤肥力的改善和提高具有积极作用。

Effects of Wheat Stubble Multiple Cropping Rape to Soil Aggregate Structure on Topsoil

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.