Deciphering Microbial Nutrient Limitation via Ecoenzymatic Stoichiometry Under Mineral Fertilization in Agroecosystems: Insights from Systematic Meta-Analysis

Mineral fertilization strongly influences soil enzymatic activity, organic carbon dynamics, and microbial nutrient limitation in agroecosystems, yet a systematic synthesis isolating the effects of mineral fertilizers alone independent of organic amendments has been lacking. This meta-analysis compiled 118 observations from 48 peer-reviewed studies (2001–2025), following PRISMA guidelines, to evaluate how nitrogen, phosphorus, and potassium and their combinations affect soil extracellular enzyme activities, soil organic carbon (SOC), dissolved organic carbon (DOC), microbial biomass C/N/P, and microbial C, N, and P limitation using ecoenzymatic vectors and stoichiometric models. Overall fertilization significantly increased soil enzyme activities, SOC, DOC, and microbial biomass C/N/P (p < 0.05–0.001), with effects varying by fertilizer combination. Ecoenzymatic vector analysis indicated persistent microbial C limitation across all treatments (vector length > 0.61). Meanwhile, vector angle and stoichiometric models confirmed sustained N and P limitation with overall fertilization and NPK significantly reducing MPL; NP significantly reducing MNL; and MCL declined only under N fertilization alone. Standardized major axis regression showed that C:N, C:P, and N:P enzyme activity slopes deviated significantly from the theoretical 1:1:1 ratio in all cases, and fertilization significantly steepened these slopes relative to controls. The N addition produced the most pronounced shift, reversing negative control slopes to strongly positive values, indicating that fertilization synchronizes microbial C-, N-, and P-acquisition strategies. These findings indicate that mineral fertilization partially alleviates microbial nutrient limitation, most effectively when nutrients are applied in balanced combinations. Meanwhile, carbon limitation remains largely unresponsive, likely reflecting its dependence on plant-derived carbon inputs rather than direct fertilization. The results provide a mechanistic framework linking ecoenzymatic stoichiometry to microbial resource allocation and support the integration of balanced fertilization strategies for optimizing nutrient cycling and soil carbon sequestration in agroecosystems.