Intercropping regulated microbial community structure in rhizosphere soil by altering microbial nutrient limitations: Evidence from proso millet/mung bean intercropping system

Abstract

Abstract Aims Soil microbes are important for explaining nutrient cycling and ecosystem functions in the green and sustainable agriculture. However, our understand of the responses of microbial communities to nutrient limitation in the farmland ecosystem remains limited.Methods We investigated rhizosphere soil microbial community structures and metabolic characteristics in proso millet/mung bean intercropping system, and further analyzed the relationship between the microbial communities and nutrient limitation based on the high–throughput sequencing.Results Compared to sole cropping, both the rhizosphere soil of two crops microbial communities were greatly limited by nitrogen (N) under intercropping system via the vector analysis, regardless of proso millet or mung bean. Linear regression analysis of soil nutrients, microbes, and threshold elemental ratio directly verified this phenomenon. Soil microbial community diversity and composition were significantly regulated by intercropping and total carbon:total nitrogen (TC:TN) and β–1,4–glucosidase:(β–1,4–N–acetylglucosaminidase + leucine aminopeptidase) (BG:(NAG + LAP)) was the key factor influencing bacterial and fungal community structure by the redundancy analysis and partial least squares path modelling, respectively. Intercropping altered the soil microbial topological properties of the networks, and the ecological connectivity of bacterial taxa was tighter than those of fungi. The microbial metabolic limitations were strongly related to community compositions, such as Proteobacteria, Actinobacteria for bacteria and Ascomycota for fungi, ultimately revealing that key functions of microbial metabolism in shaping microbial communities.Conclusions Our results highlight that the key roles of microbial nutrient limitation in optimizing community structure and ecological functions and heighten our cognition degree of soil–microbe interactions in the farmland ecosystem.