2nd UF Water Institute Symposium Abstract

Submitter's Name Debolina Chakraborty
Session Name Poster Session: Hydrologic, Biogeochemical and Ecological Processes 1
Category Hydrologic, biogeochemical and ecological processes
Poster Number 207
Author(s) Debolina Chakraborty,  Soil and Water Science Dep., University of Florida, Gainesville, FL 32611
  Vimala D. Nair,  Soil and Water Science Dep., University of Florida
  Willie G. Harris, Soil and Water Science Dep., University of Florida
  R. Dean Rhue, Soil and Water Science Dep., University of Florida
  Tool to Evaluate Soil Phosphorus Release and Potential Effect on Water Quality
  With excessive use of fertilizers, soil phosphorus (P) in agricultural lands has increased over years, contaminating adjacent water bodies. Lake Okeechobee has experienced accelerated eutrophication due to excess P loading in upland soils. Spodosols, which form the predominant soil order in Lake Okeechobee Watershed (LOW), are characterized by sandy textures, fluctuating water table, and spodic (Bh) horizons that underlie A and E horizons. Bh horizons could act as P sinks due to their high Al and Fe content. Environmental risk of P loss from soil horizons can be evaluated from P saturation ratio (PSR; molar ratio of P to [Al+Fe]), and soil P storage capacity (SPSC; calculated based on threshold PSR for a soil). SPSC is the amount of P that can be added to a given volume or mass of soil before the soil becomes an environmental concern. The objective of this study was to evaluate the efficacy of SPSC in prediction of P retention and release from Spodosols of LOW and hence its utility for hydrologic management to minimize water quality degradation. Eight Spodosol sites from the LOW were sampled by horizon. Water soluble P was determined using 1:10 soil:water ratio. Soils were analyzed for P, Fe and Al in Mehlich 1, Mehlich 3 and oxalate solutions at 1:4, 1:8 and 1:50 soil:solution ratios, respectively. Results indicate that surface horizons have minimal P retention capacity, thus enhancing P mobility from the site. Bh horizons have greater P retentive capacity. Hence depth to the spodic horizon is important for evaluating P mobility; soils with deep spodic horizons have greater susceptibility for P loss. The nature of fertilizer application and land-use patterns affect soil P dynamics. SPSC has potential to aid in prediction of P release from LOW soils and to forecast P loading levels that would jeopardize water quality.