A comparison of soil characteristics in relation to success of a restored prairie

Abstract

The Department of Energy's Weldon Spring Site began as an ordinance site and later became a uranium processing facility. Remediation of hazardous waste resulted in an on-site disposal cell and approximately 150 surrounding acres that provided an opportunity to restore a prairie, named Howell Prairie. The 150 acre prairie was established in June, 2002, including the planting of 89 native prairie species. In 2008, a study began to quantify the success of the prairie establishment. Success monitoring shows strong establishment of native prairie species in three of four plots. The fourth plot, Subarea 2C, also showed relatively high cover, but lacked grasses and supported much shorter foliage than the other three plots. It was determined that differences in the soil composition may be the cause of the lack of success in Subarea 2C because it also had light soil color, higher clay content, and lower silt content compared to the other three permanent plots. This study attempts to determine the soil characteristics at Howell Prairie and how those relate to prairie success by using a stratified sampling regime. Forty-six samples were taken, attempting to maintain a diffuse distribution of sampling points with a bias in Subarea 2C. The study measured soil grain size and texture, compaction and infiltration, nutrients, minerals with a focus on clay minerals, organic matter, soil pH, neutralizable acidity, and cation exchange capacity. Results showed the percent of silt was lower in Subarea 2C. The resulting textures showed that this area's soils were loam and clay loam, with silt loam and silty clay loam in other areas. All samples had quartz in the clay and non-clay fractions. Other non-clay minerals present included potassium feldspar and plagioclase. Of the clay minerals, several were present throughout the study area: illite, interstratified illite-montmorillonite, and kaolinite. Interstratified kaolinite-smectite was found in Subarea 2C. Most nutrients were insignificant, except phosphorus, which was lower, and magnesium was at toxic levels in Subarea 2C. It is hypothesized that a potassium amendment will reduce magnesium uptake and promote success. To demonstrate this, the potassium to magnesium ratio was studied.