Crop diversification increases soil extracellular enzyme activities under no tillage: A global meta-analysis

Abstract

Conservation agriculture with three management principles has been widely adopted to alleviate the current global agricultural soils facing threats such as soil erosion and nutrient loss. However, unclear understanding of rational crop rotation and the lack of global quantitative assessment limit our deeper insight into soil nutrient cycling under conservation agriculture. Considering the important role of soil extracellular enzyme activities (EEAs) on soil nutrient cycling, a meta-analysis with 3238 observations was conducted on the effects of no tillage (NT) and legumes incorporation into rotation system (LRS) on soil EEAs. NT significantly increased the activities of C-acquiring, N-acquiring, P-acquiring, and oxidative enzymes by 18.3%, 17.4%, 7.1%, and 14.0%, respectively, while LRS significantly increased only P-acquiring enzymes. The combination of NT and legume cultivation had no significant effect on EEAs. In contrast, crop diversity had a positive effect on the NT-induced increase in EEAs. In addition, the extent of NT-induced changes varied depending on other factors. Through further analysis, we clarified the important factors affecting NT-induced changes in EEAs, such as climatic conditions, soil properties, and agronomic practices at the experimental sites. Overall, our findings provide insights into the understanding of the mechanisms of conservation agriculture impacts on the soil nutrient cycling.