Location: Columbia Plateau Conservation Research Center
Project Number: 2074-21600-001-002-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Sep 1, 2022
End Date: Apr 30, 2027
Objective:
1. Understanding soil water use patterns of weeds and wheat
2. Refining best management practices associated with integrated chemical and mechanical weed control systems
Approach:
Objective 1. Weeds are a major biotic stressor of wheat in dryland wheat-fallow cropping systems. In low-to-intermediate precipitation regions, effective weed management during the fallow period is important in preserving and storing water for the following wheat crop. This research will evaluate the capacity of water consumption for three predominant warm-season weed species (Russian thistle (Salsola tragus), kochia (Bassia scoparia) and prickly lettuce (Lactuca serriola)) in dryland wheat production. Water use of these weeds compared to wheat will be evaluated in studies conducted in controlled conditions (growth chamber), in six-foot columns, and commercial fields. Differences in the permanent wilting point (i.e. how dry the soil can get before the plant dies) will be measured both under controlled conditions in a growth chamber and in the field in six-foot columns. The soil columns will also be used to evaluate rooting depth. Yield data from the fields will be used to assess the impact of weeds on grain production. An understanding of a potential below ground advantage for each weed species and quantification of the water extracted if weeds are left untreated after harvest will provide scientific information to farmers seeking a return on investment for controlling weeds post-harvest.
Objective 2. Effective weed management is one of the critical components to have successful wheat production cropping systems. Unfortunately, the pace of discovering new herbicides is much slower than the pace for weeds to develop resistance and the benefits of no-till agriculture are being threaten by herbicide-resistant weeds. Studies to support the chemical control with more integrated weed management strategies are needed to maintain long-term sustainability in the wheat cropping systems of eastern Oregon and inland PNW. In line with the studies with cover crops and alternative crops to intensify and diversify dryland wheat cropping systems, we propose to study how occasional tillage can possibly reduce the problem of resistant weeds without causing other past problems (soil erosion, water erosion, soil compaction, etc.). We propose to study different weed management practices in the fallow year of the common winter wheat-fallow rotation to see how it is possible to maintain sustainability in those cropping systems. The study will be established in two sites, Pendleton and Moro, with a split-plot RCBD and four replications. Both phases of the rotation will be present each year. The main plots will be to study the effect of weed management in fall and/or spring and the sub-plots will be to study the effect of two different weed managements in late summer (chemical vs. undercutter). The main treatments will be adjusted to the two locations depending on existing tillage equipment, weed problem, and preliminary results from 2022. Weeds will be evaluated in the fallow and crop phase. In the crop phase, weeds will be controlled chemically and uniformly among the different plots. In addition to the effect of weed control practices on weed infestations, soil water content at seeding time will be evaluated per sub-plot each year.
