Can Increased Cover Crop Diversity Increase Root-Soil Binding and Reduce Soil Loss During Overland Flow?

Although cover crops can potentially improve on-farm soil and water management to reduce erosion, their ability to bind soil and whether multi-species cover crops offer additional benefits has attracted little attention. This study aimed to assess the impact of cover crop diversity (Secale cereale, Brassica juncea, Vicia faba as monocultures and mixtures) on soil loss through changes in root-soil binding using rhizosheath mass an indicator in a silt loam field near Dundee, Scotland. Using a randomized block design, overland flow simulations (8 L min−1) tested soil loss across treatments, and soil cores were collected for rhizosheath and root measurements. Shoots were removed from half of the plots prior to measurements to isolate root diversity effects. Individual species identity, rather than species diversity, determined root and rhizosheath mass, with treatments containing V. faba having 64 % more root mass than the other species, and treatments containing S. cereale having 50 % more rhizosheath mass per unit of root dry mass than others. Shoot presence delayed runoff, but neither rhizosheath mass nor species diversity affected soil loss. Between-block variation in sediment concentration, total sediment and total runoff suggested that soil loss was influenced more by intra-field variability in soil structural and hydraulic properties. This work highlights how intra-field variability in soil structural and hydraulic properties can critically influence the success of erosion control measures, offering valuable guidance for future research and practical application of site-specific strategies for conserving soil function.