Cover crop diversity improves multiple soil properties via altering root architectural traits

Cover crops may influence soil health and functioning. However, little is known about the role of belowground root architectural traits in linking cover crop diversity with rhizosphere soil ecosystem properties. We hypothesize that cover crop diversity may improve root traits, which in return, could influence its effects on essential indicators of soil physicochemical heterogeneity, such as the composition of soil aggregate-size classes and nutrients, and the soil organic matter (SOM) and soil organic carbon (SOC) contents. We studied the impact of plant diversity on root traits and soil properties. The four soil aggregate-size classes, such as large macro- (>2000 μm), small macro- (<2000-500 μm), meso- (<500-250 μm), and micro-aggregates (<250 μm) were separated by the dry sieving. Root traits such as surface area (cm²) and length (cm) were quantified by image analysis using Winrhizo. The soil nutrient, SOM, and SOC contents were determined by standard methods. We used Fox's (2005) method for partitioning the selection and complementarity effects on plant productivity. Plant diversity improved productivity, root architectural traits, root coverage, the composition of soil aggregate-size classes and nutrients, SOM and SOC contents across the soil depth. It increased and decreased the relative abundance of meso- and micro-aggregates, respectively. Both root architectural traits and SOC contents positively correlated with several soil edaphic properties essential for physicochemical heterogeneity, health, and functioning. Our results suggest that competition among plant roots in species-rich than poor communities may improve rhizosphere soil carbon storage, the composition of soil aggregate-size classes, and nutrients.