The impact of landscape restoration on crop productivity and soil properties in severely eroded hilly landscapes in southwestern Manitoba

Landscape restoration is the practice of moving topsoil that has accumulated in the concave lower slope areas of the landscape and replacing it on the eroded convex upper slope positions from where it had originated. However, to date there is no known scientific literature on landscape restoration as a soil erosion and land management practice.;A large field-scale study was conducted in the undulating and hummocky landscapes of southwestern Manitoba. Four research sites, a primary site and three secondary sites were used in the study. Soil from each site was removed from lower slope positions at a depth of 10 cm (4 in) using a tractor equipped with a land scraper. The soil was then placed on eroded upper slope positions at a depth of 10 cm. The research plots were established as randomized complete block designs where each plot represented one replicate of a two treatment comparison. The upper slope pairs comprised a treatment plot (10 cm added topsoil) and a control plot (no topsoil added). Conversely, the lower slope positions comprised a treatment plot (10 cm removed topsoil) and a control plot (no removal of topsoil).;The objectives of Study 1 were (1) to determine the impact of landscape restoration on crop productivity in upper slope landscape positions where topsoil had been added and in lower slope landscape positions where topsoil had been removed and (2) to determine the net effect of landscape restoration on crop productivity within the landscape. Seedlings in topsoil addition plots were found to emerge faster and at a more consistent rate and had a 60% greater plant population compared to the control plots. At the primary research site, the addition of topsoil significantly increased crop yields by 31% in the first year post-restoration and continued to increase the following year by 64%. Yield increases also occurred at each secondary site and ranged from 10 to 133%. The effect of added topsoil on eroded hilltops was more evident during a year with below normal precipitation, as yield differences between control and addition plots were greater than yield differences in a year with above normal precipitation. At one secondary site, there was a 20% reduction in crop yield in the lower slope positions where topsoil had been removed. However, the crop yield increase that occurred in the addition plots in the upper slope positions was slightly greater than the yield loss that occurred in the removal plots. Therefore, there was still a net benefit in crop production within the landscape. When crop yields were normalized across ail research sites, yield differences between upper slope treatment plots were significantly greater than yield differences between lower slope treatment plots. Therefore, adding 10 cm of topsoil to severely eroded hilitops resulted in a net benefit in crop productivity within the landscape.;The objective of Study 2 was to determine the soil properties which contribute to increased crop production on severely eroded hilitops. Landscape restoration significantly increased nitrate nitrogen, Olsen phosphorus and, sulphate sulphur concentrations throughout the profile in topsoil addition plots. Soil organic matter concentrations were nearly 2.5 times greater in addition plots compared to control plots. Soil moisture retained at field capacity and plant available water was also significantly greater in addition and increased by 11% and 21%, respectively. Although the addition of topsoil improved the nutrient status on eroded upper slope positions, the significant increase in moisture retained at field capacity, attributed to the increased soil organic matter concentrations, likely played a major role in increasing field pea production on eroded hilitops, particularly during growing seasons with below normal precipitation. In summary, the results from this study on landscape restoration illustrate that landscape restoration is an innovative, logical, and practical land management practice to restore crop productivity on severely eroded hilitops and requires further attention from researchers and from agricultural producers. (Abstract shortened by UMI.);The overall goal of this research is to explore the practical application of landscape restoration as an alternative land management practice to restore crop productivity in eroded hilly landscapes.