Shifts in soil microbial community, soil enzymes and crop yield under peanut/maize intercropping with reduced nitrogen levels

A field experiment with five nitrogen (N) application rates (120, 140, 160, 180, 200 kg hm−2) under peanut/maize intercropping regime was conducted to evaluate cropping patterns and N application rates on yield, soil enzyme activities, and rhizosphere microbial community structure. The field experiment showed that the land equivalent ratio (LER) in maize/peanut intercropping system was not decreased as compared with the monoculture pattern, though the total N supply was approximately reduced by 20%. Terminal restriction fragment length polymorphism (T-RFLP) results showed that the treatments of intercropping (IMP100%, IMP80% and IMP60%) increased the abundance of Rhizobium hainanense, Rhizobium leguminosarum and Frankia which are associated with nitrogen fixation as compared to monoculture pattern (M100% and P100%). The qPCR results revealed that the copy number of nifH was significantly higher in the treatments of intercropping than in monoculture pattern. The result was also consistent with the T-RFLP analysis. In conclusion, peanut and maize under the condition of intercropping can promote the population of microorganisms associated with nitrogen-fixing in the rhizospheric soil. Our results provide a theoretical basis and technical support to soil N utilization, development of low carbon agriculture and protection of farmland ecological environment.