Long‐term leguminous mulch reduces microbial nutrient limitation and enhances soil multifunctionality of citrus orchard

Abstract Leguminous green mulching (LGM) enhances soil biochemical properties and ecosystem functions of orchards, yet the underlying mechanisms remain poorly understood. To address this, we compared three mulching regimes—clean tillage, 4‐year mulching, and 8‐year mulching—to examine the response of soil microbial metabolic limitation and ecosystem multifunctionality (EMF) to LGM. Results showed that soil carbon (C), nitrogen (N) and phosphorus (P) contents, corresponding enzyme activities, and EMF all increased significantly with mulching duration but decreased with soil depth. In topsoil, 8‐year mulching achieved the highest EMF during the seeding‐fruit maturity stage (2.04), followed by the withering‐fruit swelling (WFS) stage (2.00). Microbial C limitation consistently declined with mulching age, while P limitation fluctuated across growth stages and mulching treatments. Compared with clean tillage, 8‐year mulching reduced microbial C limitation by 6.69%–45.02% and P limitation by 1.59%–9.47%. Partial least squares structural equation modeling indicated that EMF was driven directly by C‐ and N‐acquiring enzyme activities and indirectly by C and N nutrient pools. Among these, C‐acquiring enzyme activity (path coefficient: 0.42) exerted the strongest synergistic effect during the WFS stage. Collectively, prolonged LGM enhanced EMF by alleviating microbial nutrient constraints, with the greatest benefits observed in topsoil and during the WFS period. These findings provide multi‐temporal and spatial evidence that LGM regulates soil nutrient supply and cycling, offering a basis for more refined and targeted orchard management strategies.