The three states in this region contend with some of the most erosive cropland in the U.S. Soils are mainly derived from loess (windblown material) and volcanic ash. The region experiences cool, wet winters and warm-to-hot, dry summers. Up to 70% of annual rainfall occurs from November through April. Water erosion is a primary concern in mid to higher precipitation areas (13 to 17 inches or more) on rolling cropland with slopes up to 45% or more. In lower rainfall areas (less than 13 inches) on coarser textured soils, wind erosion causes the primary soil loss, typically in fall and early spring. Much of the water erosion occurs during winter and is associated with rain, rain on snow or rapid snowmelt when frozen soils are beginning to thaw. Intense rainstorms during the spring and summer can also occasionally cause significant soil losses.
Winter wheat is the dominant dryland crop with significant rotation crops including: spring wheat, spring barley, pea, lentil, winter rapeseed, winter and spring canola, mustard, chickpea, alfalfa and grass seed. More than 100 different crops are grown where irrigation is available in areas with long growing seasons.

This region includes:
Idaho
Oregon
Washington

Challenges
The primary erosion problems in the region involve winter wheat planted on summer fallow in the lower precipitation zones, and winter wheat planted after low-residue crops in the higher rainfall zones.
The switch to no-till or other conservation tillage systems following a typical 2-year rotation of winter wheat-fallow or spring crops has commonly resulted in problems with winter annual grass weeds and soilborne diseases. Long, hot, and dry summers are obstacles to eco- or chemical fallow and no-till seeding of winter crops. Without the use of tillage, growers usually can't maintain adequate seed-zone soil moisture for timely

The Palouse region of Washington.

establishment of winter wheat. Tillage practices like "dust mulch" leave the soil highly vulnerable to wind erosion in late summer and fall. In higher precipitation regions problems range from low-residue crops, intensive tillage and soil compaction to wheat yields of up to 130 bushels per acre which create so much residue that establishing spring crops can be difficult.

Possible solutions
Northwest research shows expanding a 2-year winter wheat-fallow or winter wheat-pea/lentil rotation to a 3-year or longer rotation (with spring crops) effectively minimizes most pest problems.
Continuous no-till spring crops have replaced winter wheat-fallow rotations in some areas and can be successful until there is a build-up of pests associated with such rotations. Stubble mulch (mulch-till) systems for fallow can significantly reduce erosion potential. In years with favorable rainfall, spring crops can be substituted for fallow to reduce weed, disease, and erosion.
In higher rainfall areas, heavy-duty, direct-shank fertilizer applicators, modified chisels or field cultivators allow deep banding of fertilizer without prior tillage. Growers can then seed winter wheat following the application of a nonselective herbicide or cultivation for weed control.

- Thanks for assistance from Roger Veseth, University of Idaho/ Washington State University (WSU); Robert Papendick, WSU; and Don Wysocki, Oregon State University.

For more region-specific information on conservation tillage, send for one of the publications listed on page 35.