Vineyard δ15N, nitrogen and water status in perennial clover and bunch grass cover crop systems of California's central valley

Perennial cover crops offer a wide range of agronomic and environmental benefits to agroecosystems. Two such cover crops, a perennial legume (strawberry clover) and a perennial native bunch grass mix, were analyzed for water and nitrogen status in a California central valley vineyard. Soil in the rhizomatous clover cover crop system had high water content, total N, soluble N, and vegetative cover as well as low weed density compared to the soil in the bunch grass cover crop system. Similarly, grape leaves in the clover system had higher percent N and δ15N than those in the bunch grass system. High δ15N in the clover system may be due to increased rates of anaerobic denitrification and other fractionating processes associated with N turnover in the wet, N-rich system. The strawberry clover appears to be a more effective cover crop in this vineyard, where the increased N could mitigate the need for chemical fertilizers and reduce nitrate leaching into surrounding watersheds.