Effects of intercropping and soil properties on root functional traits of cover crops

Abstract

Cover crop trait diversity may enhance multiple ecosystem functions and environmental sustainability in agroecosystems, providing a mechanistic link between crop diversity and changes in ecosystem processes. In agroecosystems, root traits play a key role in functions related to soil nutrient cycling processes, but belowground traits of cover crops are poorly understood. In this study, we analyzed root functional traits of hairy vetch (V. villosa, a legume) and cereal rye (S. cereale, a grass) across five organically-managed agroecosystems in southeastern Michigan selected to span diverse soil fertility levels. Specifically, in this study we ask: (1) what is the extent of cover crop root functional trait variation and is this modified in mixture? (2) Does the expression of cover crop root traits co-vary in predictable patterns? And (3) Which soil properties best explain functional trait variability of cover crops? We found some support for root trait trade-offs; for instance, root C:N and root diameter were positively correlated for rye in mixture (p = 0.049), as were root %N and root length for rye in both mixture (p = 0.003) and monoculture (p < 0.0001). Acquisitive root traits (higher root length and specific root length) increased by 43–66% for vetch grown in mixture, and conservative traits (larger root diameter and higher C:N) were favored in monoculture. As expected, nitrogen in soil particulate organic matter pools, and plant-available phosphorus, were correlated with root trait expression across the farm gradient. These findings contribute to predictive understanding of root trait variation of cover crops across different environmental and management conditions, and inform the design of agroecosystems for delivery of belowground ecosystem services with cover crops.