Submitted to: Earth Surface Processes and Landforms
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/18/2006
Publication Date: 12/18/2006
Citation: Sharratt, B.S., Feng, G., Wendling, L. 2007 Loss of soil and PM10 from agricultural fields associated with high winds on the Columbia Plateau. Earth Surface Processes and Landforms 32:621-630. Interpretive Summary: About 2 million acres of farm land in eastern Washington and north central Oregon are maintained in summer fallow every year. Summer fallow has been proven to conserve soil water and bolster wheat production, but wind erosion from fallow land contributes to the exceedance of the US EPA National Ambient Air Quality Standard for PM10 (particulate matter '10 µm in aerodynamic diameter) in the region. During periods of high winds, as much as 2500 kg ha-1 or 1 t ac-1 of topsoil is eroded from these lands. Nearly 10% of the eroded mass is PM10. Although the loss of PM10 is relatively small compared to loss of topsoil, loss of PM10 from agricultural soils impairs air quality in the region. To avoid exceeding the EPA Standard for PM10 in urban environments, agronomists and air quality scientists must develop alternative tillage practices or cropping systems that will reduce PM10 emissions from agricultural lands in eastern Washington and northern Oregon.
Technical Abstract: Winter wheat - summer fallow is the conventional cropping system employed on >1.5 million ha-1 within the Columbia Plateau of eastern Washington and north central Oregon. Wind erosion during the 14-month fallow period contributes to poor air quality in the region, yet little is known concerning the magnitude of soil and PM10 (particulate matter '10 µm in aerodynamic diameter) loss from agricultural lands. Therefore, loss of soil and PM10 was assessed from a silt loam in eastern Washington during 2003 and 2004. Field sites were maintained in fallow using conventional tillage practices in 2003 (9-ha field) and 2004 (16-ha field) and instrumented to assess horizontal soil flux and PM10 concentrations at the windward and leeward positions in the field during high wind events. Soil flux was measured using creep and airborne sediment collectors while PM10 concentrations were measured using high volume PM10 samplers. Six high wind events occurred over the two year period, with soil loss ranging from 43 kg ha-1 for the 12-22 September 2003 event to 2320 kg ha-1 for the 27-29 October 2003 event. Suspension-sized particulates (<100 µm in diameter) comprised '90% of the eroded sediment, indicating that direct suspension and not saltation was the dominant process by which the silt loam eroded. The corresponding loss of PM10 for these two events was respectively 5 and 210 kg ha-1. Loss of PM10 comprised 9 to 12% of the total soil loss for the six events. This study suggests that the relatively small loss of PM10 from eroding agricultural fields maintained in summer fallow can impact air quality in the Columbia Plateau. Therefore, alternative tillage practices or cropping systems are needed for minimizing PM10 emissions and improving air quality in the region.