Influence of intercropping Chinese milk vetch on the soil microbial community in rhizosphere of rape

Aims In comparison to the accumulated knowledge related to the legume-cereal intercrops, very little is known on both basic and applied aspects of the legume-brassica intercrops. In fact, the potential of legume-brassica intercrops was enormous to improve crop yields, biomass, nitrogen uptake, the economic reliability via land equivalent ratio, and so on. Therefore, in the present study, the Chinese milk vetch (Astragalus sinicus L.)-rape (Brassica napus L.) intercropping system was investigated. The specific objective of this study was to investigate how Chinese milk vetch affects the soil microbial community in rhizosphere of rape. Methods A series of bucket experiments based on Chinese milk vetch-rape intercrops, included root separation and straw mulching, were employed to explore the soil properties and soil microbes in rhizosphere of rape. Results Intercropping substantially decreased the organic carbon content and the total nitrogen content and changed the C/N ratios. Intercropping also decreased the soil microbial biomass in rape rhizosphere (including the total PLFAs, bacteria, actinomycete, AM-fungi, and so on). In addition, intercropping and straw mulching also changed the structure of soil microbial community in rape rhizosphere, which was significantly correlated with 16:1w9c and 18:3w6c (6, 9, 12). At the same time, under the influence of intercropping Chinese milk vetch, soil microbial functional activity in rape rhizosphere was significantly reduced. Soil microbial community functional composition in rape rhizosphere was also changed greatly by intercropping, which was significantly correlated with D-glucosaminic acid and g-1-phosphate under no straw mulching, and glycogen, D-xylose and 2-hydroxy benzoic acid under straw mulching. Conclusions Intercropping Chinese milk vetch decreased soil microbial biomass and functional activity and changed greatly the soil microbial community structural and functional composition in rape rhizosphere. Our findings revealed that root interaction between Chinese milk vetch and rape was a crucial factor to manage the crop intercropping, which might, in turn, determine the soil microbe on rhizosphere.