Proceedings of the 2020 Mississippi Water Resources Conference

Year: 2020 Authors: Yasarer L.M W., Stevens E., Taylor J., Locke M.

Wetting and drying of soils can alter chemical compositions and result in nutrient transformations that lead to more labile phosphorus. Mississippi Delta soils are generally high in phosphorus content and may experience several wet-dry cycles throughout the year, as well as periods of inundation due to flooding conditions. This study was designed to estimate the potential phosphorus fluxes that may occur when dry soils are re-wetted and remain submerged in water for various residence times. Soils/sediments were collected from two locations within five different habitats (cropland, restored cropland (i.e. CRP), forest/riparian wetland, sediment retention pond, and drainage ditches) within Beasley Lake Watershed, Mississippi. Sample locations were selected to include locations that typically experience ephemeral standing water, such as topographic depressions within the cropland, CRP, and forest areas. All soil/sediment samples were dried, ground, and sieved for consistency. Samples were inundated with water and incubated at 5, 15, 25 and 30°C to represent different seasonal temperatures throughout the year. Residence times of 4, 8, 12 and 48 hours were used to estimate the kinetic properties of the phosphorus fluxes. In addition, soils were analyzed for pH, bulk density, and totals of carbon, nitrogen, phosphorus, manganese, calcium, iron, aluminum, and sulfur. Sequential phosphorus extractions of dry, field moist, and flooded soils were also performed to determine how phosphorus was stored in the soil and potential conditions that would release phosphorus into the environment. Preliminary results indicated that forest soils had the highest phosphorus concentrations of all the habitats. Sequential extractions revealed that both drying and flooding the soils increased phosphorus availability.