Most studies about the effects of N addition on soil microbial biomass evaluate soil microbial and physicochemical characteristics using single-test methods, and these studies have not been integrated and analyzed to comprehensively assess the impact of N fertilization on soil microbial biomass. Here, we conduct a meta-analysis to analyze the results of 86 studies characterizing how soil microbial biomass C (MBC), N (MBN), and P (MBP) pools respond to exogenous N addition across multiple land use types. We found that low N addition (5–50 kg/hm²) rates significantly affect soil microbial biomass, mainly by increasing MBC but also by decreasing MBP and significantly increasing MBC/MBP. N addition affects soil physicochemical properties, significantly reducing pH and significantly increasing the soil dissolved organic N and inorganic N content. Our analysis also revealed that the effects of N application vary across ecosystems. N addition significantly decreases MBP and total P in planted forests but does not significantly affect soil microbial biomass in grasslands. In farmland soil, N addition significantly increases total P, NH₄⁺, NO₃⁻, MBN, and MBP but significantly decreases pH. Although N addition can strongly influence soil microbial biomass, its effects are modulated by ecosystem type. The addition of N can negatively affect MBC, MBN, and MBP in natural forest ecosystems, thereby altering global ecosystem balance.

The primary purpose of our study is to clarify the differences in physicochemical properties and microbial community composition with the continuous evolution of soil utilization types. Here, we used natural forest soil (NS), healthy banana garden soil (HS), diseased banana garden soil (DS), and paddy soil (PS) in tropical areas of Hainan Province to conduct this study. According to our research, the abundance and diversity of soil bacteria (HS/DS and PS) decrease significantly as soil utilization types evolve. In healthy banana soil, the amount of Actinobacteria and Firmicutes at the bacterial phylum level is more significant than in other soil utilization types. It was observed that the bacterial community structure in NS was notably distinct from that in HS and PS. Apart from paddy soil, the bacterial makeup of the other two soil utilization types mainly remained consistent. Pathogenic soil (DS) undergoes significant changes in its chemical properties. These changes are primarily seen as decreased pH and organic carbon content and increased C/N and inorganic nitrogen content (NH₄⁺, NO₃⁻). This suggests that a specific type of microorganism (Fusarium oxysporum f. sp. cubense) can cause a significant shift in the soil environment, leading to an unexpected change in soil type. Therefore, to ensure that the soil is healthy, we must balance the soil microbial community composition, promote the increase of the beneficial microbial species and quantity, and create an environment suitable for microbial growth.