Long Term Monitoring of Wind Erosion Induced Changes to Soil Properties in Western Kansas

Abstract

The wind erosion process selectively removes smaller and lighter particles, leaving coarser and denser particles behind. These smaller and lighter particles typically represent the more fertile fraction of the soil which includes the organic component. In addition, changes in soil texture and organic matter can affect soil structure and water holding capacity. The limited research available indicates that surface soil textures become coarser and organic matter decreases over time under wind erosion. Limited data exists on the rate of selective removal by wind of soil components over time and subsequent effects on soil quality. The objective of this ongoing study is to determine the long term changes in soil particle size and organic matter resulting from wind erosion in western Kansas, an area historically susceptible to wind erosion. The surface soils of ten sites in western Kansas were sampled in 1948 by W.S. Chepil and analyzed for particle size and organic matter. Based on Chepil's location descriptions, these same sites were again sampled in 1984 (Lyles and Tatarko, 1986) and again in 1996, 2001, 2006, and 2011. All samples were taken within approximately 3 m (10 feet) of the original sampling points. Samples were analyzed for particle size distribution (texture) and organic matter content in the surface. Land managers were also surveyed to determine management history of each site and possible effects of land use on long term soil changes. For the 1948 samples, clay content was determined using a hydrometer, sand by sieving, and silt by difference. Organic matter was determined by the USDA NRCS National Soil Survey Laboratory, Lincoln, Nebraska, using the Walkley-Black titration method. Subsequent samples (post 1948) were analyzed for particle size by the pipette method, sand fraction by sieving, and silt content by difference. Post 1948 samples were also analyzed for organic matter at the Kansas State University Soil Testing Laboratory using the modified Walkley-Black method. Results show that changes in the measured properties are related to management on the ten study sites. The 1984 samples showed an average increase in sand content of 7.9% for nine of the sites sampled while silt content had an average decrease of 9.2% compared to the 1948 samples. An average decrease in organic matter of 0.6% for 8 of the sites studied was also observed. Since water erosion is not a problem on these nearly level sites and because the study area has historically experienced severe wind erosion during the Dust Bowl and after, the soil property changes were assumed to be primarily a result of selective removal by wind erosion. In addition, clean tillage was practiced by most of the land managers during the early period which leaves little protective vegetative material on the surface. Beginning in the late 1980’s to the mid 1990’s however, management histories show a transition to a greater emphasis on residue management including undercutting, mulch tillage, and one site planted to continuous grass under the CRP program. Following these changes in management, sand contents have stabilized while silt contents and organic matter contents generally increased. Wind erosion was likely causing an increase in sand and a decline in silt content and organic matter in these soils in the decades between 1948 and 1984, with potentially detrimental effects on soil structure, nutrient availability, and water-holding capacity. Subsequent adoption of conservation tillage and residue management has stabilized and in some cases reversed this trend in soil property changes.