Tuesday, November 6, 2007 - 1:35 PM
206-2

Soil and Water Conservation Challenges for Agriculture in the Inland Pacific Northwest.

William F. Schillinger1, Robert I. Papendick1, and Donald K. McCool2. (1) Washington State Univ., Dept. of Crop and Soil Sciences, Dryland Research Station, Lind, WA 99341, (2) USDA-ARS, 253 L.J. Smith Hall, Pullman, WA 99164

Soil and water conservation has been a major concern in the Inland Pacific Northwest since the onset of farming 125 years ago.  Some of the highest historic water erosion rates in the USA occurred on steep slopes in the Palouse region where soil loss averaged 45 Mg ha1 yr-1 and could reach 450 Mg ha-1 yr-1.  Rapid snowmelt or rain on thawed soil overlying a frozen layer causes the worst water erosion, especially on newly-planted winter wheat (Triticum aestivum L.) fields following grain legumes that produce little residue.  The primary concerns with water erosion are heavy loss of topsoil from 2 million ha of croplands and the accompanying degradation of water quality.  Heavy soil loss and degradation of air quality from wind erosion are the major concerns in the 1.5 million ha of croplands comprising the dry (< 300 mm annual precipitation) winter wheat – summer fallow cropping zone.  Here drought, excessive tillage, low production of crop residue, poorly aggregated soils with low organic matter content, and occasional high winds leave soil vulnerable to blowing.  These soils are dominated by particles < 75 um in diameter that are readily suspended and transported for long distances.  Significant advances in water and wind erosion control have occurred in the past 30 years.  Most approaches involve management of the soil surface and crop residues.  Today's powerful tractors and modern implements allow farmers to conduct field operations in a timely manner. Effective use of glyphosate and other herbicides has largely reduced the need for repeated tillage operations and, on some farms, eliminated the need for tillage.  Numerous research advances and increased technical know-how, combined with economic incentives by government farm programs and energy costs have fueled an ongoing steady shift to conservation-till and no-till farming.