Variation in soil properties and crop yield across an eroded prairie landscape

Intensive tillage moves large quantities of soil, resulting in a pattern of soil redistribution where topsoil is depleted from convex slope positions and deposited in concave positions. In these experiments, the variation in erosion estimates, properties of the surface soil, and crop yield (four years) were determined in an undulating landscape that is subject to annual moldboard plowing. Results indicated that areas with high tillage erosion (shoulder slope positions) had high inorganic carbon contents in the surface soil due to the incorporation of calcareous subsoil material. Wheat yields in 2000, 2001, and 2003 were lowest in these areas, demonstrating yield reductions of 50 percent or more. Conversely, wheat yields were highest in areas in which soil translocation by tillage and water results in a net deposition of soil (depressions). These areas had a deeper A horizon, and the surface soils had higher organic carbon contents, lower pH and lower inorganic carbon contents. Soybean yields in 2002 did not show a strong dependence on location within the landscape. These results indicate that the observed variation in crop yield in undulating landscapes may be significantly influenced by removal of topsoil through repeated intensive tillage, and point to opportunities for landscape restoration to reduce yield losses.