Phenolic acids released to soil during cereal rye cover crop decomposition

Authors: OTTE, BRIANA - University Of Maryland; Rice, Clifford; Schomberg, Harry; TULLY, KATHERINE - University Of Maryland; Mirsky, Steven

Submitted to: Chemoecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/30/2019
Publication Date: 2/1/2020
Citation: Otte, B., Rice, C., Schomberg, H.H., Tully, K., Mirsky, S.B. 2020. Phenolic acids released to soil during cereal rye cover crop decomposition. Chemoecology. 20:25-34. https://doi.org/10.1007/s00049-019-00295-z.
DOI: https://doi.org/10.1007/s00049-019-00295-z

Interpretive Summary: The rise of herbicide resistance in weeds is contributing to a greater interest in combining other weed management practices with herbicides. This is because our current herbicides are not as effective, or completely ineffective, and there are currently no new chemistries coming to market. Cover crops are particularly receiving a lot of attention for their physical effects (mulches). There is additional interest in examining the toxicity of compounds that are released from both living and terminated cover crops (chemical effect). Cereal rye is of particular interest as it has been shown to have some toxicity on small seeded summer annual weeds. Little work has been done to investigate the concentrations of phenolic acids released from cereal rye. There is also much less known on how much is released from the roots versus the shoots. A field experiment examining root and shoot contributions of phenolic acids to soil was examined in Beltsville, Maryland in 2015. Cereal rye roots, not shoots, were found to be the primary contributor of phenolic acids to soil. Further, soil phenolic acid concentrations had a nominal response to tillage and soil depth. Overall, the phenolic acids concentrations increased in soils during the first 3-7 days after cereal rye termination and then decreased to initial concentrations after 56 days. Our research provides insights for future allelopathic research. Specifically, there is a need to understand root release of phenolic acids. This work will provide improved methodology for researchers investigating the role of allelopathy in weed suppression.

Technical Abstract: Aims Cereal rye (Secale cereale) cover crops are becoming widely used in agricultural systems to provide many agroecosystem services. Cereal rye allelochemical effects on weed suppression has become a priority in light of the global herbicide-resistant weed epidemic. This study examined the relative contribution of allelochemicals (phenolic acids) from cereal rye shoots and roots to soil during decomposition. Methods A field experiment examining root and shoot contributions of phenolic acids to soil was examined in Beltsville, Maryland in 2015. Soil, sampled to 10 cm, was analyzed for phenolic acids, over time, using liquid chromatography-mass spectrometry. Results Cereal rye roots, not shoots, were found to be the primary contributor of phenolic acids to soil. Further, soil phenolic acid concentrations were little affected by tillage or soil depth. Overall, the phenolic acids concentrations increased in soils during the first 3-7 days after cereal rye termination and then decreased to initial concentrations after 56 days. Conclusions Our research provides insights for future allelopathic research. Specifically, there is a need to understand root release of phenolic acids. Building this body of knowledge is critical to incorporate allelopathy as part of a multi-tactic weed management system.