Submitted to: Journal of Soil and Water Conservation Society
Publication Type: Abstract Only
Publication Acceptance Date: 3/15/1996
Publication Date: N/A
Technical Abstract: Tillage operations on slopes of steep cropland can move substantial quantities of soil, decreasing topsoil depth on ridgetops or at the upper boundary of tilled areas, and increasing its depth elsewhere, particularly on toeslope positions. Evidence of tillage soil movement and its affect on topsoil depth is abundant in the steep, non-irrigated wheatlands of the Pacific Northwest, USA, even though this region was first intensively cultivated no earlier than 1890. The moldboard plow has been traditionally used in this region. Due to slow tractor speeds and low power, the furrow slice was turned downhill, thus maximizing the opportunity for tillage soil movement and soil degradation. The objective of this study was to estimate the mass of soil displaced downslope through moldboard plowing and to compare estimated soil movement with measured deposition at field boundaries. We conducted an experiment using buried magnets and flat washers to quantify the statistical relationship between soil movement and slope steepness. Linear regression was used to determine the relationships between soil movement to slope steepness and by measuring topsoil depth along sapling transects that included benchmark elevations. Using the regression equation, we estimated soil movement to be approximately 4-4.2 sq. m., well within the range of measured field deposition (2.2 to 6.0 sq. m.). The current variation in topsoil depth along hillslopes can be attributed in large part to the affects of tillage soil movement. This trend must be halted to maintain agricultural productivity.