Document Type

Thesis

Date of Degree Completion

Winter 2024

Degree Name

Master of Science (MS)

Department

Cultural and Environmental Resource Management

Committee Chair

Dr. Robert Hickey

Second Committee Member

Dr. Carey Gazis

Third Committee Member

Dr. James Johnson

Fourth Committee Member

Dr. Holly Pinkart

Abstract

Most Triticum aestivum (winter wheat) producers in the drylands of Douglas County, Washington, use a crop-fallow rotation system with conventional tillage (CT) and many have farmland in Conservation Reserve Program (CRP) status. CT has known negative environmental consequences, and no tillage/direct seed (NT) is recommended by the USDA as the preferred alternative. However, this recommendation is based on studies involving large geographic areas of the inland Pacific Northwest with varied soils and environmental conditions that have produced mixed results regarding efficacy of NT in improving soil health. Additionally, no work has been done on the effects of CRP status on soil health in this area. This research seeks to fill knowledge gaps relating to the effects of CT and NT tillage treatments and CRP status on soil health in low-precipitation drylands using a small geographic area (Mold, Douglas County, Washington) with the same soil and environmental conditions. Physical, chemical, and microbiological soil health indicators (SHIs) were measured in 5cm increments to 20cm depth at CRP, CT, NT, and an anthropogenically unaltered control site during the 2021-2022 growing season. NT is preferable to CT for preventing aeolian erosion, preserving soil texture, increasing soil moisture retention, reducing soil temperatures, enhancing organic carbon and total nitrogen soil stocks, and supporting microbial populations with increased functional capacities for preserving soil structure and fixing carbon and nitrogen. CT is preferable to NT for reducing microbial populations of pathogens. Some expected differences in SHIs were not found between tillage treatments, which the researcher attributes to the limited time since conversion from CT to NT at that site. Placing farmland in shrub steppe CRP status without regard to the original grassland conditions at Mold does not restore soil health to the native condition or improve overall soil health to levels where returning the land to T. aestivum production would be advisable.

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