211-2 Assessment of the Phosphorus Index for Louisiana.



Tuesday, October 18, 2011
Henry Gonzalez Convention Center, Hall C, Street Level

William Felicien, Agricultural Chemistry, LSU AgCenter, Baton Rouge, LA and Lewis Gaston, Plant, Environmental and Soil Sciences, LSU AgCenter, Baton Rouge, LA
Measured loss of phosphorus (P) in runoff from small plots (1.5 m2, simulated rain) was compared to P loss ratings calculated with the Louisiana P-index.  Study sites included pasture (hay field and grazed) and forest (timber and timber + straw harvest) on coastal plain soils that are typical for the poultry-producing region of the state.  Results showed poor correlation between P in runoff and P loss ratings, partly due to high losses despite low P loss ratings for grazed pasture.  Considerably higher P often appeared in runoff from forest soil than expected based on soil P desorption, and the source of this P may have been the forest litter layer.  Difficulty in predicting P loss based on mechanistic approaches supports use the P-index.  However, better understanding of mechanisms responsible for P loading into runoff should lead to improvements in the P-index and better practices for controlling P loss to surface water.
See more from this Division: ASA Section: Environmental Quality
See more from this Session: Evaluation and Validation of P Indices