Soil properties and productivity as affected by topsoil movement within an eroded landform

Abstract

In hilly landforms subject to long-term cultivation, erosion has denuded upper slope positions of topsoil and accumulated topsoil in lower slope positions. One approach to remediate these eroded landforms is moving soil from areas of topsoil accumulation to areas of topsoil depletion, termed here soil-landscape rehabilitation. These experiments were conducted in an eroded undulating landform typical of the prairie pothole region. The summit, shoulder, upper and lower backslope were depleted in soil nutrients and organic carbon and had enriched inorganic carbon contents through the incorporation of calcareous subsoil material into the tilled layer. Surface soil organic carbon contents in lower slope positions were at least twice that in the most eroded positions. Six replicate plots were established that extended from the summit to the toeslope of the test area. Soil-landscape rehabilitation was performed on three plots by moving 15–20 cm of soil from the lower slope (footslope and toeslope) to the upper slope (summit, shoulder, and upper backslope) positions. The three remaining plots were undisturbed. In lower slope positions, soil properties were shifted upwards with respect to the soil surface by 15–20 cm in rehabilitated plots (where soil was removed). In upper slope positions, soil properties were shifted downwards by 15–20 cm in rehabilitated plots (where soil was applied, original soil was buried). After rehabilitation, the top 15 cm of soil in rehabilitated plots had characteristics similar to the footslope and toeslope, from which the soil was taken. Thus, soil properties were much more uniform from summit to toeslope in rehabilitated plots compared to undisturbed plots. Productivity was measured in two cropping years characterized by summer drought conditions. In rehabilitated plots, yields were relatively consistent across landscape positions, whereas in undisturbed plots, yields were depressed in eroded landscape positions. Grain yields in rehabilitated plots were increased by 30% in areas of soil addition. These yield increases were accompanied by yield decreases of 50% (year 1) and 20% (year 2) in areas of soil removal. Results indicate that movement of accumulated topsoil from lower slope positions to eroded upper slope positions can result in large yield increases in upper slope positions and more consistency in crop yields across the landscape, but additional research is needed to provide a more complete analysis of the soil productivity impacts of this approach.