Positive Effects of Intercropping on Soil Phosphatase Activity Depend on the Application Scenario: A Meta-Analysis

Phosphorus (P) availability generally limits crop productivity in agroecosystems and is closely linked to soil organic P mineralization by phosphatases secreted by plant roots and soil microbes. Intercropping is a sustainable alternative for efficiently improving crop productivity. However, the response of soil phosphatase activity to intercropping and the variations in this response with agronomic and climate/soil conditions remain unclear. This meta-analysis of 120 studies across agroecosystems shows that intercropping significantly improves soil phosphatase activity, plant total P uptake and yield by 18 %, 8 % and 8 %, respectively, implying that intercropping can alleviate P limits on crop productivity. The positive effect of intercropping with legumes and woody plants on soil phosphatase activity is greater than that of intercropping with gramineous plants and forbs. However, both inorganic and organic P fertilizer application reduces the positive effect of intercropping on soil phosphatase activity, particularly under intercropping with legumes. The promotion of soil phosphatase activity by intercropping is weaker in arid areas where mean annual precipitation is lower than 600 mm. The positive correlations of soil phosphatase activity with both plant total P uptake and yield further emphasize the importance of high organic P mineralization for plant growth in intercropping systems. Overall, our results indicate that the effect of intercropping on soil phosphatase activity is influenced by intercropping type, application of P fertilizers, microbial biomass and climatic factors, and this meta-analysis provides a theoretical reference for choosing suitable intercropping systems to achieve yield increase and sustainable development.