Short-term perennial peanut integration into bahiagrass system influence on soil microbial-mediated nitrogen cycling activities and microbial co-occurrence networks

Integration of perennial peanuts into warm-season grasslands offers a potential solution to reduce nitrogen (N) fertilizer input and enhance N cycling through soil microbial activities. There is limited information on the changes in soil microbial diversity and communities following the short-term integration of rhizoma perennial peanut (RPP; Arachis glabrata Benth.) into warm-season perennial bahiagrass (Paspalum notatum Flüggé) as well as its impact on N cycling processes. This study investigated changes in N cycling populations and soil microbial communities in bahiagrass-RPP mixtures compared to their monocultures at <2 years after RPP establishment in Spring (March) and Fall (October) seasons. Real-time qPCR was used to quantity N functional groups in the soil involved in nitrification, denitrification, and N₂ fixation. DNA amplicon sequencing was employed to examine co-occurrence networks of soil microbes, while activities of soil enzymes [N-Acetyl-β-d-glucosaminidase (NAG) and leucine aminopeptidase (LAP)] involved in N mineralization were also measured. Bahiagrass-RPP mixtures had no effect on N cycling genes. Ammonia oxidizing archaea were the major ammonia oxidizing prokaryotes compared to ammonia oxidizing bacteria in bahiagrass-RPP systems. We found that bahiagrass-RPP mixtures exhibited greater prokaryotic alpha diversity and NAG activities than RPP monoculture. Meanwhile, RPP influenced soil fungal community composition (beta diversity) and enhanced the relative abundance of dominant soil fungal genera (Fusarium, Gibberella, and Humicola). The presence of RPP in bahiagrass systems led to increased negative microbial interactions in microbial occurrence networks. Greater complexities in microbial networks were linked to forage growth season, which was related to enrichment of the relative abundance of Basidiomycota. Our findings showed that RPP has the potential to influence N cycling process in bahiagrass system by altering the abundance of certain N cycling microbes, especially fungal taxa, within 2 years of RPP establishment.