Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/24/2025
Publication Date: 2/24/2025
Citation: Peterson, C.M., Mirsky, S.B., Schomberg, H.H., Thompson, A.I., Tully, K.L. 2025. Cover crop termination method has a limited effect on spring soil moisture and temperature in humid mid-Atlantic U.S. Agricultural Water Management. http://doi.org/10.1016/j.agwat.2025.109342.
DOI: http://doi.org/10.1016/j.agwat.2025.109342

Interpretive Summary: Cover crops are plants grown on agricultural fields in the off-season to provide a variety of agroecosystem benefits, such as reduced soil erosion and improved nutrient cycling. In the eastern United States, cover crops are typically grown during the winter fallow period and killed the following either with broad-spectrum herbicides or roller-crimpers that mechanically kill cover crops and create a uniform horizontal mulch for planting cash crops. Past research has found higher soil water content in soils under rolled, horizontal cover crop mulch compared to cover crops left standing, but it is unclear if this pattern persists when roller-crimping is paired with herbicides. The moisture content and temperature of the soil under a cover crop residue is important because it impacts biological activities essential to commercial crop production, such as seed germination, seedling growth, and nutrient release from decomposing organic matter. To address this question, we measured changes in soil moisture and temperature over time in one field with very sandy soil and another with very clayey soil for two years during the six weeks following cover crop termination. No differences were found in soil moisture dynamics between either herbicide or roller-crimping treatments; however, soil surface temperature was impacted by roller-crimping. Daily temperature fluctuations at the soil surface were consistently greater under the roller-crimped cover crop residue than residue left standing vertically, indicating an insulating effect. These findings are helpful for farmers making complex cover crop management decisions, such as termination timing and methods, especially in years with above- or below-average precipitation.

Technical Abstract: Winter cover crop termination is commonly achieved by applying broad-spectrum herbicides, which vary in mode of action and time required to kill the cover crop. Many growers also use roller-crimpers to mechanically kill cover crops or to create a uniform horizontal mulch for planting cash crops. The influence of mechanical termination methods on soil moisture and temperature has been previously evaluated, but not paired with chemical termination as frequently is the case in farming operations. To address this question, soil moisture and temperature were measured continuously in central Maryland, USA, across five weeks under a cereal rye (Secale cereale L.) cover crop terminated via roller-crimper and the application of glyphosate and paraquat. Over two years, there were minimal to no differences in cumulative infiltration or evapotranspiration among termination treatments at two fields with contrasting soil textures. In all four site-years, daily temperature flux was higher in roller-crimped residue (17.3 °C) compared to standing (15.0 °C). The divergence of these findings from previous studies may be the result of delaying cover crop termination to anthesis for successful roller-crimping, allowing the cereal rye to accumulate biomass and create a thicker mulch layer than in earlier field trials. In humid regions such as the mid-Atlantic United States, growers should not expect to see meaningful differences in soil moisture or temperature between mechanical or chemical termination methods. However, soil moisture and thermal dynamics might shift depending on termination strategy in arid regions or years with less-than-average precipitation.