Spatial and temporal variabilities on soils in St. Landry Parish, Louisiana

The spatial and temporal variation of soil properties was evaluated on three sites in close proximity to Bayou Wikoff, St. Landry Parish, Louisiana. A total of 1,068 surface (0-5 cm) samples were collected, geo-located, and transported to Louisiana State University for physical and chemical analyses. Physical and chemical properties were spatially and temporally displayed using ArcGIS. Interpolation techniques such as spline, kriging, and inverse distance weighting were evaluated to determine the best fit model for the project. Spline and inverse distance weighting were found to be the least accurate interpolation models. Kriging provided the most accurate model of spatial and temporal data distribution. Clay content (for total suspended solid control), P levels, and organic C % were a primary focus for this study, as potential non-point source pollution threats to water quality in Bayou Wikoff. All three sites were evaluated individually, as each had unique management practices. Pasture Site 1 exhibited larger concentrations of nutrient deposition proportional to increasing organic C % and clay content in areas of lower elevation. These areas were nearest to the bayou and potentially allowed for runoff, reducing water quality. Pasture Site 2 has artificial swale formations that affected the distribution of the evaluated properties. Extensive research at this site exhibited patterns of nutrient distribution that correlated with the swale formations. In the low portion of the swale, clay content, organic C %, and corresponding nutrient concentrations increased. The Pristine Site, used as a control site, showed evidence that the surface soil (0-5cm) was heavily altered from natural deposition as a result of being turned, moved, or replaced. Overall, spatial and temporal assessments revealed that while the three sites have unique distribution patterns of clay and organic C %, the soils are not hazardous for water quality. However, best management programs should focus on swales and low lying areas to determine the affect of spatial variability