4th UF Water Institute Symposium Abstract

Submitter's Name Biswanath Dari
Session Name Poster Session: Water quality protection and treatment
Poster Number 72
Author(s) Biswanath Dari,  Graduate Student (Presenting Author)
  Vimala D Nair,  Research Professor
  Rao Mylavarapu, Professor
  Willie G Harris, Professor
  Model Parameters from Soil Test Data for Input into Phosphorus-loss Predictive Models
  Florida sandy soils are susceptible to phosphorus (P) loss from an agricultural or animal production system into nearby water bodies via surface or subsurface pathways. Leaching is a predominant mode of P transport from these soils. Chemical equilibrium models often use the P bonding strength (Langmuir KL) or the Freundlich coefficient (KF) to predict P release from a soil. If KL or KF can be obtained from an oxalate or a soil test solution, it would offer an easy means of obtaining “K” for modeling. Phosphorus LEAching from Soil to Environment (PLEASE) is a simple P loss predictive model based on P sorption mechanism in a soil and its potential movement into surface water. Our objective was to relate the P saturation ratio (PSR) to isotherm parameters based on the hypothesis that KL or KF will be related to the PSR as determined from P, Fe and Al concentrations in an oxalate solution. Isotherms were constructed on soil samples collected from A, E and Bt horizons of a manure-impacted dairy sprayfield and KL and KF values were computed. All soils were analyzed for P, Fe and Al in an oxalate extract. Results indicated that there is a relationship between PSR and Langmuir KL or Freundlich KF suggesting that it might be possible to obtain these “K” values from P, Fe and Al in an oxalate solution for input into the PLEASE Model. The Model uses P adsorption parameters, precipitation, soil test phosphorus and groundwater height as inputs to predict loss of P. Performance of PLEASE model might be comparable with other reliable methods for estimating P loss from an agricultural system into surface water.