4th UF Water Institute Symposium Abstract

Submitter's Name Asmita Shukla
Session Name Poster Session: Water quality protection and treatment
Poster Number 35
Author(s) Asmita Shukla,  Southwest Florida Research and Education Center, University of Florida (Presenting Author)
  Sanjay Shukla,  Southwest Florida Research and Education Center, University of Florida
  James Knowles, Southwest Florida Research and Education Center, University of Florida
  Role of Agricultural Detention Areas in Phosphorous Retention: Sink or Source?
  Agricultural Detention Areas (ADAs) cover about 6% of the total farm area on a global scale however, they have not been well studied and documented in the past. This study focusses on Phosphorus (P) retention by an ADA located in the Everglades basin in south Florida. Water quantity and quality at the ADA was monitored for two years between August 2008 and August 2010. Water quantity monitoring included measurement/estimation of pumped inflow, rainfall, evapotranspiration, outflow, storage, and seepage. Water quality monitoring included inflow and outflow sampling and analysis of Total Phosphorus (TP). Contrary to the common belief that these systems work as a water quality Best Management Practice, ADA worked as a source of P during Year 1. It released 17% more P than what came in with pumped inflow and rainfall which resulted in an increase of 12% in the mean incoming P concentration. However, during Year 2 (Y2), ADA worked as a sink of P and retained 53% of the total incoming P load. Change in function from source to sink on an annual basis was mainly attributed to variable water retention and rainfall in conjunction with limited to negative soil P retention capacity. Soil samples (0-10 cm) analyzed for Mehlic-1 extractable Iron, Aluminum, and P were used to calculate Soil Phosphorus Storage capacity (SPSC). Majority of soil in the area had low to negative SPSC indicating limited to no soil P adsorption capacity. Year 1 was marked by a tropical storm which led to a large rainfall in a short span of time. Unusually high water levels inside the ADA after the tropical storm resulted in dilution of TP in the incoming farm drainage. This dilution effect combined with limited P storage capacity of the ADA soil led to the release of P.