Location: Columbia Plateau Conservation Research Center
Project Number: 2074-21600-001-013-A
Project Type: Cooperative Agreement
Start Date: Sep 1, 2025
End Date: Aug 31, 2026
Objective:
1. Refining best management practices associated with integrated chemical and mechanical weed control systems.
2. Validating precision spray technology for chemical control of weeds in dryland wheat-cropping systems.
Approach:
Herbicide-resistant weeds are a threat to agricultural productivity nationwide with significant consequences to no-till crop systems. As the pace at which weeds develop resistance surpasses that for the discovery of novel herbicides for control, new technologies and practices are necessary for effective weed management and conservation of current herbicide chemistries. Chemical control with integrated weed management strategies is a potential option to maintain long-term sustainability in the wheat cropping systems; however, information is lacking for dryland regions of eastern Oregon and the inland PNW. Research in Objective 1 will evaluate the efficacy and sustainability of different weed management practices applied during the fallow year of the common winter wheat-fallow rotation. The study will determine whether occasional tillage is efficient in reducing herbicide-resistant weeds. The study will be conducted at two sites in Oregon (Pendleton and Moro) under intermediate and low annual precipitation. The main plots will be used to study the effect of weed management in fall and/or spring and the subplots will be used to study the effect of two different weed managements in late summer (herbicides [chemical] vs. undercutter tillage [mechanical]). Weeds will be evaluated in the fallow and crop phase. In the crop phase, weeds will be controlled chemically and uniformly for all plots. In addition, soil water content will be evaluated per subplot each year in spring and fall.
Precision weed management (i.e., precision spraying) is another option to combat herbicide resistance. The Weed-IT precision sprayer system offers several advantages over uniform herbicide application including reduced herbicide use and water consumption, and economic potential to use more expensive herbicides to prevent resistance and increase weed control. Research in Objective 2 will evaluate the efficacy and accuracy of the Weed-IT system in dryland wheat-fallow cropping systems. The study will contrast uniform herbicide application with the Weed-IT system using both high and low sensitivity settings since newly growing weeds may evade detection, whereas established weeds may not obtain adequate coverage. Accuracy of the Weed-IT system will be determined by comparison of the weed maps and application volumes generated by the Weed-IT system to maps generated from multispectral and thermal imagery from a small-unpiloted aerial system (sUAS). Potential economic benefit will be assessed for the three methods based on herbicide cost and application volume.
Overall, this research will lead to the development of advanced dryland production practices to increase profitability, conserve the soil, enhance soil water storage, promote soil health, and decrease reliance on herbicides in the U.S. Pacific Northwest.