Effect of Nitrogen Addition on Tiger Nut (Cyperus esculentus L.) Rhizosphere Microbial Diversity and Drive Factions of Rhizosphere Soil Multifunctionality in Sandy Farmland

Nitrogen (N) is an essential element both affecting rhizosphere microorganisms within soil and supporting plant nutrition; however, little is known about how the rhizosphere microbial community composition of tiger nut in sandy soil responds to nitrogen addition. In this study, high-throughput sequencing technology is employed to analyze the shifts in composition and co-occurrence networks of rhizosphere microbial communities in tiger nut after nitrogen addition in sandy farmland. Results reveal that nitrogen addition significantly increases several soil parameters, including total organic matter (SOC, 32.2%), total nitrogen (TN, 46.2%), alkali-hydro nitrogen (AN, 92.7%), beta-1,4-glucosidase (BG, 12.6%), L-leucine aminopeptidase (LAP, 8.62%), beta-1,4-xylosidase(XYL, 25.6%), and beta-1,4-N-acetylglucosaminidase (NAG, 32.3%). Meanwhile, bacterial alpha-diversity decreases with nitrogen addition, while fungi remain unaffected. Network analysis indicates a reduction in connections between microorganisms; however, increasing stability is observed in the interaction network after nitrogen addition. Importantly, nitrogen addition leads to the enhancement of rhizosphere soil multifunctionality, with fungal diversity identified as the primary driver of soil multifunctionality. The positive impact of microbial diversity on soil multifunctionality outweighs the relative negative effects. This study sheds light on the nuanced effects of nitrogen addition on rhizosphere microbial diversity and its consequent impact on soil multifunctionality, with Acidobacteria, Proteobacteria and Ascomycota having positive effects, providing a comprehensive understanding of the complex environmental-plant-soil-microbe interactions in sandy farmland ecosystems.