Neither chemical nor mechanical termination methods impact decomposition of late-killed mature cereal rye

Authors: PETERSON, CARA - University Of Maryland; Mirsky, Steven; Schomberg, Harry; TULLY, KATE - University Of Maryland

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/16/2025
Publication Date: N/A
Citation: N/A

Interpretive Summary: Cover crops are plants that are grown when no cash crop is present. The mulch created by terminated (i.e. killed) cover crops can provide benefits to a following cash crop such as weed suppression and soil moisture conservation that improve yield. Cover crops can be terminated using herbicides and/or a roller-crimper (where a large drum with steel blades is rolled across the cash crop field to mechanically damage the cover crop). There has been a need to evaluate the impact of termination method on how long cover crop residues remain as a mulch on the soil surface. We conducted a field experiment in Maryland to evaluate the impact of two common broad-spectrum herbicides (glyphosate and paraquat) with and without roller-crimping on cover crop residue breakdown. Herbicide treatment had no effect on residue quantity or quality (i.e. chemical composition). Six weeks after termination, the ratio of lignin to nitrogen was higher in the standing cereal rye samples than in the roller-crimped residue among all site-years, indicating greater decomposition had occurred in the roller-crimped residue (i.e. it was decomposing relatively faster). This work demonstrates that a mature cereal rye cover crop killed in late spring will decompose slowly regardless of chemical or mechanical termination method. This knowledge gives farmers different options for cover crop termination.

Technical Abstract: Agroecosystem benefits provided by a winter cover crop are proportional to plant residue quantity and decomposition rate. For growers who plant cover crops to suppress weeds and conserve soil moisture during the cash crop growing season, it is important to understand how management decisions such as cover crop termination method impact residue quantity and quality over time. A decomposition study was conducted in Maryland, USA at two field sites with differing soil textures in 2022 and 2023 to test the impact of two broad-spectrum herbicides frequently used for cover crop termination before cash crop planting. At anthesis, cereal rye (Secale cereale L.) plots were either mechanically terminated with a roller-crimper or left standing. One week later, chemical termination treatments (glyphosate and paraquat) were applied to half of both the rolled and standing plots. After plant death, the cereal rye biomass was sampled and placed in mesh litterbags, which were then retrieved at 2, 4, 6, 8, and 12 weeks after chemical termination treatments were sprayed and at corn harvest. No differences in decomposition rates were observed when biomass loss was calculated by calendar date or by heat units. In some site-years, roller-crimped cereal rye had higher concentrations of lignin and holo-cellulose. No differences in residue chemistry between the chemical termination herbicides were detected. Residue of mature cereal rye terminated late in the spring will decompose slowly regardless of termination method, maintaining a persistent mulch during the cash crop season.