Crop yield and weed community response to cover crop termination strategies under organic management in the US Mid-South

Authors: CARDOSO, ABMAEL - University Of Wisconsin; Nieman, Christine; POPP, MIKE - University Of Arkansas; CARTWRIGHT, KELLY - United Soybean Board; SCHAFER, JOSEPH - Winrock International; ASHLOCK, LANNY - United Soybean Board; THOMAS, ANDY - University Of Missouri; KIRKSEY, BRUCE - Agriliance; HALLER, STEPHEN - Natural Resources Conservation Service (NRCS, USDA); Libohova, Zamir; Owens, Phillip; Ashworth, Amanda; KOHMANN, MARTA - University Of Wisconsin; FRANCO, JOSE - Savanna Institute

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/20/2026
Publication Date: 4/7/2026
Citation: Cardoso, A.S., Nieman, C.C., Popp, M.P., Cartwright, K., Schafer, J., Ashlock, L., Thomas, A.L., Kirksey, B., Haller, S., Libohova, Z., Owens, P.R., Ashworth, A.J., Kohmann, M.M., Franco, J.G. 2026. Crop yield and weed community response to cover crop termination strategies under organic management in the US Mid-South. Agronomy Journal. https://doi.org/10.1002/agj2.70362.
DOI: https://doi.org/10.1002/agj2.70362

Interpretive Summary: Effective cover cropping termination strategies are crucial for the success of weed control and cash crop productivity in organic cropping systems. ). In conventional systems, the use of herbicides to terminate cover crops is a common practice, but in organic systems, this practice is not allowed and tillage, grazing, and crimping can provide effective cover crop termination. However, there is a limited understanding of how these cover crop termination strategies influence plant populations, weed composition and canopy cover, and subsequent yield of the cash crop in organic row-crop systems in the mid-south. This study evaluated the effects of four cover crop termination strategies, tillage, grazing, grazing plus tillage, and roller-crimping. The results of the study showed that all cover crop termination strategies were effective in managing the cover crop independent of tillage system. However, only tillage was effective at managing weeds in cash crops. Low cover crop biomass did not provide the residue needed to provide weed control in the roller-crimped treatments and the integration of grazing did not provide any benefit to weed control or cash crop yield. Further studies should focus on cover crop species that are more resilient to drought and on managing strategies, such as investigating contrasting sowing dates, aiming for greater biomass production.

Technical Abstract: One of the primary concerns with adopting reduced tillage practices in organic row crop systems is increased weed pressure. In the mid-south, research is lacking to address this concern for growers in the region. This study evaluated the effects of different organic cover crop termination strategies on cash crop population, weed canopy, and yield over three years (2021–2023). The experiment was arranged as a randomized complete block design with four treatments: (1) a conservation system where the cash crop was drilled into a fall-planted cover crop then terminated with a roller crimper in spring; (2) and (3) two integrated livestock-crop systems where the fall cover crop was grazed and the cash crop was either no-till planted immediately after grazing or planted following tillage after grazing; and (4) a double-cropping system in which the fall-planted crop was harvested for grain, and the subsequent cash crop was planted following tillage. Experimental units were 0.12-ha with 4 replicates per treatment. The fall-planted cover crop was cereal rye (Secale cereale L.) in years 1 and 3, and wheat in year 2. The cash crop was soybean [Glycine max (L.) Merr.] in years 1 and 3, and sorghum [Sorghum bicolor (L.) Moench] in year 2. Cash crop populations and canopy cover using modified Daubenmire method and species composition were assessed at 2 and 6 weeks post-planting each year. Tillage consistently influenced cash crop plant density across all years. Grazing affected the relative canopy cover of cash crops in all three years. The composition of dominant weed species varied annually. Redroot pigweed (Amaranthus retroflexus L.), curly dock (Rumex crispus L.), and bromegrass (Bromus spp.) canopy cover were influenced by tillage, while Johnsongrass [Sorghum halepense (L.) Pers.] was the predominant weed species across all evaluations. In 2023, neither grazing nor tillage significantly affected sorghum yield; however, conventional tillage consistently produced the highest yields overall. All cover crop termination strategies were effective at terminating the cover crop as measured by canopy cover during the duration of the study, but the observed increase in weed populations was problematic in the no-till treatments.