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United States Department of Agriculture

Agricultural Research Service

Title: Long-Term Erosion Trends on Cropland in the Pacific Northwest

Authors
item McCool, Donald
item Roe, R - USDA-NRCS

Submitted to: ASABE Annual International Meeting
Publication Type: Proceedings
Publication Acceptance Date: September 2, 2005
Publication Date: December 2, 2005
Citation: McCool, D.K., Roe, R.D. 2005. Long-Term Erosion Trends on Cropland in the Pacific Northwest. ASAE Pacific Northwest Section Meeting. September 22-24, 2005, Lethbridge, Alberta, Canada. Paper No. PNW05-1002. Available: http://asae.frymulti.com/request.asp?search=1&JID=8&AID=20047&CID=smppnr&v=&i=&T=1

Interpretive Summary: Winter erosion from non-irrigated cropland in the Inland Pacific Northwest appears to have decreased during the past 20 Water Years (WY) (1986 through 2005). Is this decrease real and if so, is it due to climate cycle or shift or changes in farming practices? A 43-year data set obtained from monitoring winter erosion on a large number of sample fields in Whitman Co, WA from WY 1940 through 1982, provides an opportunity to examine historic trends in erosion and corresponding climate conditions. During this period, the winter wheat/summer fallow crop rotation was used on much of Whitman County, including the higher precipitation zone more suitable for annual cropping. We examined daily freeze/thaw cycles, length and severity of frozen periods, snow accumulation during cold periods, and rain during early stages of the thawing process. There were several consecutive years in the 43-year data set when erosion was low. Weather records for these years indicate reduced freeze/thaw activity with little rain or snowmelt during thaw. Analysis of 1983 through 2005 climate data also indicate reduced erosion hazard from freeze/thaw effects. USDA progress records for 1979 and 1994 indicate increased application of conservation practices in 1994 as compared to 1979, with a resulting large estimated reduction in erosion. Sediment measurements at the mouth of the Palouse River show a large sediment reduction from the 1962 through 1971 period to the 1993 to 1996 period. Sediment in runoff and flooding from snowmelt on frost impacted soil occurred in WY 1996 and WY 1997, but cropland erosion rates were not catastrophic. Data indicates erosion rates have decreased over the past 20 years, and the cause appears to be a combination of improved farming practices and climate changes or cycles.

Technical Abstract: Winter erosion from non-irrigated cropland in NW Oregon, SE Washington, and N Idaho appears to have decreased during the past 20 Water Years (WY) (1986 through 2005). Is this decrease real and if so, is it due to climate cycle or shift or changes in farming practices? A 43-year data set obtained from monitoring winter erosion on a large number of sample fields in Whitman Co, WA from WY 1940 through 1982, provides an opportunity to examine historic trends in erosion and corresponding climate conditions. During this period, the winter wheat/summer fallow rotation was used on much of Whitman County, including the higher precipitation zone more suitable for annual cropping. We examined diurnal freeze/thaw cycles, length and severity of frozen periods, snow accumulation during cold periods, and rain during early stages of the thawing process. There were several consecutive years in the 43-year data set when erosion was low. Weather records for these years indicate reduced freeze/thaw activity with little rain or snowmelt during thaw. Analysis of 1983 through 2005 climate data also indicate reduced erosion hazard from freeze/thaw effects. USDA progress records for 1979 and 1994 indicate increased application of conservation practices in 1994 as compared to 1979, with a large estimated reduction in erosion. Measurement of sediment at the mouth of the Palouse River indicated a large reduction from the 1962 through 1971 period to the 1993 to 1996 period. Sediment in runoff and flooding from snowmelt on frost impacted soil occurred in WY 1996 and WY 1997, but cropland erosion rates were not catastrophic. Data indicates erosion rates have decreased over the past 20 years, and the cause appears to be a combination of improved farming practices and climate changes or cycles.

Last Modified: 12/21/2014
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