Submitted to: International Soil Conservation Organization Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/28/1996
Publication Date: N/A
Interpretive Summary: Downslope displacement of soil by tillage implements operated on contour can remove productive topsoil and expose poor quality soil on ridgetops and steep slopes. These processes are apparent in the Palouse Region of the Pacific Northwest, USA, even though the area has been farmed for little more than one hundred years. Measurements of soil displacement with one plowing of a moldboard plow were used to estimate total displacement over the years of cultivation. These estimates on a number of sites were approximately equal to deposits at selected lower field boundaries where water erosion was negligible. The size of the deposits indicates need to halt or reverse the process or recovery will be slow and expensive.
Technical Abstract: Mechanized tillage operations can move substantial quantities of soil, particularly on steep slopes such as farmed in the Pacific Northwest of the USA. The result is exposure of less productive subsoils on hilltops and gradual movement of these subsoils to bury topsoils farther downslope. This study quantified lateral soil movement with a moldboard plowing on contour at various slope steepnesses. Deposition at downslope field boundaries was determined by soil coring. Calculated downslope soil movement by plowing during the 100 years of mechanized cultivation approximately balanced the field boundary deposition. The quantities calculated help to explain the large amount of low productivity subsoil currently exposed on ridgetops of the area. Turning the plow furrow upslope or using no till or non inversion tillage will prevent additional degradation and permit some degree of recovery.