Combining compound fertilizer with organic fertilizer regulates root nutrient via rhizosphere soil enzyme activities and microbial communities in Moso bamboo forests

The combination of compound fertilizer and organic fertilizer is an effective way to improve soil fertility and promote plant growth in the agricultural and forestry production process. To demonstrate the how compound fertilizer (CF) decrement and organic fertilizer (OF) application affects fine root nutrient traits, rhizosphere soil enzyme activity and microbial community structures in Moso bamboo forests, this study replaced compound fertilizer nitrogen (N) with equal-N organic fertilizer at five substitution ratios of 0, 25%, 50%, 75%, and 100% (CF, OF25, OF50, OF75, and OF), along with a no fertilization control (CK). The results showed that compared with CK, the combined CF and higher proportions of organic fertilizer (OF50, OF75, OF) increased root N, phosphorus (P), rhizosphere soil organic carbon (SOC), N and P availability, as well as the activities of C- and N- acquiring enzymes, and the C:P EEA and N:P EEA ratios. Organic fertilizer addition also significantly changed soil bacterial, fungi community structure and increased the relative abundance of Pseudomonadota, Acidobacteriota and Mucoromycota. The enzyme quantification vector model indicated that soil microorganisms were primarily limited by N, with OF75 and OF treatments alleviating this N limitation. Additionally, PLS-SEM revealed that fertilization positively influenced enzymatic activities while negatively impacting microbial diversity, ultimately exerting a positive effect on root P. Our study indicates that the application of organic fertilizer improves rhizosphere SOC content, N and P availability, C- and N-acquiring enzyme activities, and microbial community structure, thereby alleviating N limitation of soil microorganisms, enhancing root P content, and promoting the sustainable management of soil and Moso bamboo forests.