Phenolic acids released to soil during cereal rye cover crop decomposition

Cereal rye ( Secale cereale ) cover crops supply many agroecosystem services in cropping systems including the provision of allelochemicals for weed suppression. Understanding the distinction between root and shoot relative contributions of these allelochemicals (such as phenolic acids) should provide better insight for residue management following termination of a cereal rye cover crop. A field experiment examining root and shoot contributions of phenolic acids to soil was conducted in 2015 at Beltsville, Maryland. Tissue and soil (0–10 cm) phenolic acid concentrations were analyzed over time using liquid chromatography–mass spectrometry. Cereal rye roots were found to be the primary contributor of phenolic acids to soil. Further, soil phenolic acid concentrations were unaffected by tillage or soil depth. Overall, the phenolic acid concentrations of coumaric > vanillic > 4-hydroxybenzoic acid increased in soils during the first 3–7 days after cereal rye termination and then decreased to initial concentrations after 56 days. Our research forms a basis for future allelopathy research. Specifically, there is a need to understand the contribution of roots to phenolic acid release in soils. Building this body of knowledge will improve our ability to employ allelopathy as part of a multi-tactic weed management system.