Palouse Ecological Province





In Oregon, the Palouse Province includes the gently sloping to rolling cultivated area northeast of Pendleton that surrounds the Pendleton Branch Agricultural Experiment Station and the towns of Adams and Athena. The province extends northeast to just north of Weston and just east of Milton-Freewater. It also extends into the state of Washington. In Oregon, it covers about 112,000 acres, all in Umatilla County.



Practically all of this province in Oregon is farmed. It is the only sizable area in eastern Oregon in which annual cropping under dryland conditions is successful, due to the favorable climate and good soils. Wheat and green peas for canning, grown in alternate years, is the common crop rotation. However, the climate is suitable for growing other crops that require 15 inches or more annual precipitation. Some areas are irrigated by sprinkler.

Elevations in the Oregon portion of Palouse Province are mainly between about 1,350 and 2,000 feet, and the topography is sloping to rolling or slightly hilly. Oregon’s portion of the province contrasts topographically with the area known as the “Palouse” which is farther north in Washington and northern Idaho. The Palouse is steeply rolling and hilly. Annual cropping is practiced in both locations.



Major soils of the Palouse Province in Oregon are Walla Walla silt loam, high-precipitation phase, and Athena silt loam. These soils were formed in aeolian deposits that reportedly were blown south during the era of receding glaciers farther north, in Washington.

Surface layers of Walla Walla high-precipitation phase are dark grayish brown silt loam about 12 inches thick. Subsoil is dark brown silt loam about 48 inches thick. Depth to basalt bedrock or laminated sediments is from 40 inches to more than 5 feet. Surface layers of Athena series are very dark brown silt loam about 26 inches thick. Subsoil is dark brown silt loam about 20 inches thick. The substratum is dark yellowish brown silt loam to more than 5 feet in depth and is commonly calcareous.

These dark-color soils reflect the favorable climate in which they were formed in thick aeolian deposits. They are very productive under dryland farming. It is very likely that, before cultivation, these soils produced a Palouse Prairie natural grassland dominated by Idaho fescue and resembling the existing natural grasslands near Findley Buttes in Wallowa County.



Based on data from two official weather stations in the Oregon segment of Palouse Province, the average annual precipitation for the area is 18.2 inches of which about 54% falls during winter and 40% during the growing season of adapted farm crops, March through July. Average January maximum and minimum temperatures are 38.3 and 24.1°F, respectively. Average March through July maximum and minimum temperatures are 71 and 43.5°F, respectively.

Comparing precipitation and temperatures for the two Palouse Province stations in Oregon and two official weather stations in adjacent Columbia Basin Province, very near the line of demarcation, substantiates significant reasons why darker soils have evolved under Palouse Province climate than under the Columbia Basin Province climate (Table 30). The comparison also helps explain why annual dryland farming is possible in Palouse Province but the climate of Columbia Basin Province requires summer-fallow dryland farming. Furthermore, such crops as green peas can be grown in rotation with small grains in Palouse Province, whereas only small grains, mainly wheat and barley, are produced under wheat/summer-fallow farming in Columbia Basin Province.

Under the relatively mild winter temperatures of these two provinces, the key climatic factor is 15 or more inches of precipitation annually with a significant portion of that during the farm crop growing season, i.e., a pattern typical of Palouse Province.







Management Implications

Essentially, all land in Palouse Province in Oregon is privately owned; some is owned by Native American families and leased out to established farming operations.

Soil erosion in winter, when some lands are essentially bare and surface layers often are frozen, is a concern because this area lies within a storm pattern that sometimes produces sudden precipitation. Sloping lands along the eastern portion of the province near the Blue Mountains are especially susceptible to erosion and sometimes to hail damage during thunderstorms about harvest time in late summer.

Annual wheat yields in Palouse Province in Oregon are significantly greater than in Columbia Basin Province. In addition, lands in Columbia Basin Province normally produce an agricultural crop every other year, but lands in Palouse Province normally produce an agricultural crop every year.


Province Demarcation

Palouse and Blue Mountain Demarcation

The line of demarcation between Palouse and Blue Mountain provinces in Oregon is on the line separating the Athena soil series in Palouse Province from the Waha and Couse soil series in Blue Mountain Province.75 This line is at about 2,000 feet elevation about 4 miles east of Milton-Freewater. The line continues southwest to just north of Weston and then south and west to just north of Cayuse on the Umatilla River. It is in this vicinity that the Palouse, Blue Mountain, and Columbia Basin provinces join.

Palouse and Columbia Basin Demarcation

From Cayuse, the line of demarcation between Palouse and Columbia Basin provinces runs westward on the bench north of Umatilla River for about 3 miles and then veers north across Wildhorse Creek to the vicinity of Helix. Here, the line of demarcation is on the line separating the Walla Walla silt loam high-precipitation phase, which typifies Palouse Province, from Walla Walla silt loam association, which typifies Columbia Basin Province.75 About 3 miles north of Helix, the line of demarcation heads east at about 2,000 feet elevation to a point about 2 miles south of Milton-Freewater. From there it turns to the northeast, passing just east of Milton-Freewater, to enter the state of Washington. Milton-Freewater is in Columbia Basin Province.