Pacific Northwest Conservation Tillage Handbook Series No. 29
Chapter 2 - Conservation Tillage Systems and Equipment, May 2004

Cropping Systems Research in the World’s Driest Rainfed Wheat Region

Authors: Wiliam Schillinger, Douglas Young, Doug Rowell, Harry Schafer, and Steve Schofstoll

William Schillinger, Harry Schafer, and Steve Schofstoll, Dept. of Crop and Soil Sciences, Washington State University, Dryland Research Station, PO Box B, Lind, WA 99341; Douglas Young, Dept. of Agricultural and Resource Eocnomics, Washington State University, 101 Hulbert Hall, Pullman, WA 99164; Doug Rowell, Benton County Association of Wheat Growers, 100 McKinley Spring Rd., Prosser, WA 99350. Corresponding author (schillw@wsu.edu).

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ABSTRACT
Winter wheat - summer fallow (WW-SF) is the predominant cropping system in the 300,000-acre Horse Heaven Hills (HHH) region in south-central Washington, USA. Blowing dust from residue- and roughness-deficient summer fallow results in soil loss and causes health problems. Annual no-till cropping to replace summer fallow would provide year-round protection against wind erosion. A 6-year field study conducted from 1996 to 2002 evaluated the agronomic and economic feasibility of continuous annual no-till hard red spring wheat (HRSW) as an alternative to traditional WW-SF. Long-term average annual precipitation at the experiment site is 6 inches, which we believe is the lowest for any nonirrigated wheat region of the world. Annual precipitation during the study ranged from 4.4 to 9.5 inches and averaged 6.0 inches when two wet years were followed by a 4-year drought. Russian thistle heavily infested HRSW plots and depleted soil water during the two wet years. Seed-zone water content in summer fallow was sufficient to plant WW in late August in only two of six years. Average (6-year) grain yield was 17.7 bu/acre for WW-SF (one crop every two years) and 7.9 bu/acre for annual no-till HRSW. The number of kernels per head had a significant contribution to yield during years of acute water stress. Net economic returns for annual HRSW lagged WW-SF by an average $38 per acre per year. Although continuous annual no-till cropping has clear environmental advantages, it is not economically competitive with WW-SF given current technology in the Horse Heaven Hills.

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