Intercropping of kura clover (Trifolium ambiguum M. Bieb) with prairie cordgrass (Spartina pectinata link.) enhanced soil biochemical activities and microbial community structure

Abstract Optimizing the use of N fertilization is the major factor for establishing perennial grasses to enhance the biomass production and soil health under marginally yielding croplands. A study was conducted to investigate the influence of N fertilization and intercropping of kura clover (Trifolium ambiguum M. Bieb) (KC) with prairie cordgrass (PCG) (Spartina pectinata Link.) on soil biochemical activities and microbial community structure. The fertilization treatments included four N levels: 0, 75, 150, and 225 kg N ha−1, and the grass-legume intercropping system included one grass (PCG) and one legume (KC) (PCG-KC). Data showed that soil microbial biomass C (MBC) was 90 and 55% higher with PCG-KC than the PCG-225N and PCG-75N, respectively. Enzyme activities associated with life processes of microorganisms and release of mineral nutrients from organic matter were the highest in PCG-KC, and were comparable to that observed under medium to high N fertilization. The results indicated that PCG-KC intercropping could sustainably provide soil health benefits compared to the N fertilization. The PCG-KC combination led to an increase in total PLFA (phospholipid fatty acid) and total bacterial PLFA concentration relative to the PCG-0N, PCG-75N and PCG-225N. The PCG-KC also had the highest glomalin-related soil protein content (11.9 mg g−1) indicating high abundance of Arbuscular mycorrhizal fungi crucial for P nutrition. Further, N deficiency as well as high N fertilization appear to reduce the abundance of N-fixing bacteria as indicated by the presence of nifH amplicons. In summary, PCG-KC intercropping yielded comparable or more desirable soil microbial community structure and enzymatic activities compared to the N fertilization. Considering the cost and negative impact of N fertilization on the environment, intercropping KC with PCG can be desirable for improving soil health of marginally yielding croplands.