BROOKINGS, S.D. -- Unlike water erosion, tillage erosion is not strongly affected by slope length. Therefore, in hilly regions that have many changes in slope, tillage erosion can be the dominant erosive force, explains Thomas Schumacher, retired South Dakota State University plant science professor.
"Tillage erosion is the downslope movement of soil by tillage," he says. "During tillage, soil is lifted and gravity moves soil downslope. Soil movement by tillage increases with slope steepness. However, net soil transport by tillage is determined by the change in slope. Soil movement by tillage very slowly levels the land surface. Soil is removed from areas where slope is increasing (convex) and deposited in areas where slope is decreasing (concave)."
He adds that this applies in the eastern Dakotas, western Minnesota and throughout the Prairie Pothole Region.
Conditions that Schumacher says influence tillage erosion include: intensive tillage; the tillage operation -- implement design; depth, speed, and direction of tillage; topography -- curvature, change in slope, steepness; and soil properties -- bulk density and soil texture.
"Any implement that lifts the soil will cause tillage erosion," he says. "Some secondary operations are as erosive as primary tillage operations."
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Soil changes
Tillage erosion degrades soil quality in upper slope positions.
"The additive effect of years of combined tillage, water and wind erosion is shallow topsoil in the upper slope (sometimes with exposed subsoil) and deep topsoil accumulation in depressions," Schumacher says.
He adds that erosion also changes soil organic matter content, soil texture, water holding capacity, nutrient availability, aeration, pH and other soil properties that affect productivity.
When it comes to productivity changes resulting from tillage erosion, Schumacher says tillage erosion depletes crop yield in areas of soil loss.
"In our studies, plant growth and yield was linked to changes in soil properties induced by soil movement by tillage," he says. "We measured yield in an eroded prairie landscape for four years -- three years of wheat and one year of soybean -- and found that grain yields in the most eroded portions of the field were consistently less than half of the yield in non-eroded areas."
Effects on management
In the eastern Dakotas and western Minnesota, research shows long-term tillage has increased the land area with poor-quality topsoil.
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"Crop yields on eroded land reflect soil properties. Approaches to reduce the effects of soil erosion on productivity are being investigated, including precision agriculture and targeted application of manure and other soil amendments," he says.
To learn more, visit www.iGrow.org .
