Non-leguminous green manures improve labile phosphorus availability and crop yield in agroecosystems: A global meta-analysis

Incorporating the green manure (GM) approach in agroecosystems enhances phosphorus (P) availability and reduces mineral P-fertilizer input. Despite global promotion, a comprehensive global synthesis of the GM effect on soil P fractions is lacking. To address this gap, we conducted a meta-analysis of 48 published studies to evaluate the impact of climatic, edaphic, and agronomic variables on soil P fractions, enzyme activities, subsequent crop yield, and P uptake under a GM cropping system. Overall, GMs significantly increased the labile P fraction (n = 592) by 18 % compared with fallow management. Non-leguminous GMs showed a 21 % increase in labile P, resulting in an 18 % increase in subsequent crop yield and a 30 % increase in subsequent crop P uptake compared with fallow. Leguminous GMs stimulated soil enzyme activities, elevating acid phosphatase (ACP) by 40 % and β-glucosidase by 182 % compared with fallow. Compared to no-till (NT), GMs under conventional tillage (CT) significantly increased soil enzyme activities, including ACP, alkaline phosphatase (ALP), β-glucosidase, as well as subsequent crop yield, and P uptake. Long-term GM incorporation (5–10 yrs) significantly reduced moderately labile P by 25 %, leading to increased labile P fraction. Linear regression analysis demonstrated a positive correlation between labile P and soil organic carbon (SOC), but a negative with mean annual precipitation (MAP) and mean annual temperature (MAT). These findings suggest that incorporating GMs into a CT management system can potentially accelerate soil P cycling by promoting soil enzyme activities, enhancing subsequent crop production, and providing an alternative approach to reducing mineral P-fertilizer dependency. This approach exemplifies sustainable food production practices and underscores the significance of GMs for long-term agricultural resilience and soil health worldwide.