Herbicide-resistant weeds are becoming a significant challenge for farmers in the semiarid Central Great Plains, particularly in wheat–sorghum–fallow rotations. Weeds like kochia and Palmer amaranth are becoming increasingly difficult to control every year, and new herbicide options are limited. Recent research in Kansas suggests that cover crops may offer a way forward.
At Kansas State University's Agricultural Research Center in Hays, researcher Sachin Dhanda put his work to the test in Kansas fields. With support from a SARE grant, he explored how fall- and spring-planted cover crops could suppress weeds in wheat–sorghum–fallow systems. Advised by Dr. Vipan Kumar and Dr. Anita Dille, the team found that pairing cover crops with the right herbicides can improve weed control while protecting yields.
Key Findings
- Fall cover crops help. Triticale, peas, rapeseed, and radish planted in the fall cut weed density by up to 80% and weed biomass by more than 70% compared to chemical fallow.
- Spring cover crops pack a punch. Oats, barley, and peas planted in spring suppressed weeds by as much as 99%. Even weeks after termination, they kept weed pressure down.
- Crop yields held steady. In most cases, wheat yields with cover crops matched those under chemical fallow.
- Economics is tricky. Fall-planted cover crops may lower short-term profits but provide effective weed control and long-term benefits, including slowing herbicide resistance.
Recommendations
- Pair cover crops with residual herbicides to get the strongest weed control.
- Stay flexible. Tools such as precision spraying, drones, and harvest weed seed control may improve economics in the near future.
- Think long-term. Even when returns are modest, cover crops can build resilience and reduce weed pressure over time.
Dhanda explained that the project "shows that cover crops, when paired with residual herbicides, can effectively control problematic weeds. My advice is to stay flexible when integrating cover crops and to adopt an integrated weed management approach for managing herbicide-resistant weeds."
Although fall-planted cover crops lowered short-term profits compared to chemical fallow, Dhanda noted that they effectively controlled weeds and offer long-term benefits, including slowing herbicide resistance, diversifying weed management, and reducing reliance on limited herbicides, stating "While short-term profitability may be a challenge, this research provides valuable knowledge that can help farmers make informed decisions and build more resilient cropping systems for the future."
He added, "With continued research, optimization of CC practices, and financial support through programs like USDA NRCS Environmental Quality Incentives Program (EQIP), these practices can contribute to more sustainable and profitable farming systems in the Central Great Plains."
View Related SARE Grant:
- Integrating Fall- and Spring-Planted Cover Crops for Weed Suppression in semiarid Central Great Plains (GNC22-346)