Integrating Fall- and Spring-Planted Cover Crops for Weed Suppression in semiarid Central Great Plains

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Commodities

• Agronomic: triticale

Practices

• Crop Production: cover crops, no-till
• Pest Management: cultural control, integrated pest management, weed ecology

The widespread evolution of herbicide resistance in weeds poses a serious management challenge to growers in the semiarid Central Great Plains. Glyphosate-resistance has been widely reported in kochia (Bassia scoparia L.) and Palmer amaranth (Amaranthus palmeri L.) populations (two predominant weed species in the region). Furthermore, multiple herbicide resistance has also been reported in both weed species. Lack of cost-effective and alternative new herbicide sites of action (SOA) further exacerbate the problem of herbicide-resistant (HR) weeds and threaten the long-term sustainability of prevailing cropping systems in this region. Increasing herbicide costs to manage HR weeds has recently renewed research efforts to build a strong rationale for developing ecologically based integrated weed management (IWM) strategies in the region. Cover crops are known to suppress weed growth along with improvement in the soil health. However, there is currently limited information on the impact of cover crops grown in no-till (NT) dryland wheat-based crop rotation (wheat-sorghum-fallow) on the weed suppression, soil weed seedbank dynamics, soil water budget, crop yields and overall farm profitability. This proposed study will quantify the impact of fall vs. spring-planted cover crop management strategies on: 1) suppression of HR weeds (including kochia and Palmer amaranth), soil seedbank dynamics, and weed population shifts, 2) herbicide selection pressure (herbicide load) to mitigate/delay the resistance evolution, and 3) soil water budget and subsequent crop yields in NT dryland production system. This project aims to develop innovative, ecological-based, and economically sustainable weed management practices in the region, which will have long-term implications for reducing the over-reliance on herbicides and minimizing adverse environmental effects by implementing site-specific herbicide-resistance mitigation tactics.

This project will provide several learning and action outcomes mainly focused on profitability and quality of life. Regarding learning outcomes, growers will increase their profitability by effective management of HR weeds and save two to three herbicides application cost. Regarding action outcomes, utilizing cover crops for weed suppression will improve environment quality by reducing herbicides use for weed control. Indirectly, it will help in decreasing herbicide runoff into the environment, and it will reduce the selection pressure for further evolution of herbicide resistance in weed populations. The anticipated audience for this information is growers who can integrate cover crops in their cropping system for effective weed management. The growers in the western Kansas will be directly benefited; however, the data will be applicable to the growers throughout the CGP region. The outcomes will be measured by conducting a survey to see how likely growers who attend the field day demonstrations will implement these cover crop-based weed management practices on their production farms.