Weed suppression using cover and alternative crops in dryland wheat-fallow systems of eastern Oregon

Authors: BARROSO, JUDIT - Oregon State University; SINGH, SURRENDA - Oregon State University; HAGERTY, CHRISTINA - Oregon State University; Reardon, Catherine - Kate; MACHADO, STEPHEN - Oregon State University; GOURLIE, JENNIFER - Oregon State University; PRITCHETT, LARRY - Oregon State University; KRIETE, LINNEA - Oregon State University; HARRISON, KYLE - Oregon State University; Umbarger, Stephen - Steve

Submitted to: Spanish Society of Weed Science
Publication Type: Proceedings
Publication Acceptance Date: 4/4/2022
Publication Date: N/A
Citation: N/A

Interpretive Summary: Limited precipitation in eastern Oregon has led to the common practice of fallowing for 15 months to conserve soil moisture and maximize yield for the following crop. Although fallowing is important in storing soil water, it is associated with negative effects on soil health, erosion, and carbon compared to annual cropping. The objective of this research focuses on the intensification and diversification of the conventional wheat-fallow (WF) cropping system to improve soil health and reduce fertilizer and herbicide inputs. This article includes preliminary data for the first and second year of a three-year study. Trials with ten cover crop (CC) and nine alternative crop (AC) treatments and four replications were established in two rainfall zones, intermediate (400 mm annually) and low (220 mm annually), in eastern Oregon where winter wheat is the predominant cash crop. Among the winter CCs studied, peas competed with weeds better than lentils when cultivated as single species or in a mixture with barley at both sites. Among the spring CCs, phacelia and spring barley as single species produced lower amounts of weed infestation, particularly at the intermediate site. At the low rainfall site, the spring CCs did not generate differences in weed infestation due to a lack of significant biomass. Peas were the most competitive AC, in part due to the herbicide options for grass control in the legume crops.

Technical Abstract: Limited precipitation in eastern Oregon has led to the common practice of fallowing for 15 months to conserve soil moisture and maximize yield for the following crop. Although fallowing is important in storing soil water, it is associated with negative effects on soil health, erosion, and carbon compared to annual cropping. The objective of this research focuses on the intensification and diversification of the conventional wheat-fallow (WF) cropping system to improve soil health and reduce fertilizer and herbicide inputs. This article includes preliminary data for the first and second year of a three-year study. Trials with ten cover crop (CC) and nine alternative crop (AC) treatments and four replications were established in two rainfall zones, intermediate (400 mm annually) and low (220 mm annually), in eastern Oregon where winter wheat is the predominant cash crop. Among the winter CCs studied, peas competed with weeds better than lentils when cultivated as single species or in a mixture with barley at both sites. Among the spring CCs, phacelia and spring barley as single species produced lower amounts of weed infestation, particularly at the intermediate site. At the low rainfall site, the spring CCs did not generate differences in weed infestation due to a lack of significant biomass. Peas were the most competitive AC, in part due to the herbicide options for grass control in the legume crops.