A phosphorus index is a semi-quantitative to qualitative model for assessing the potential for loss of soil and fertilizer phosphorus (P) to ground and surface water, therefore,eutrophication risk. The concept of a P Index is recent and popular, with most states having developed a P Index that is either a simplification or extension the original 1993 concept. The Louisiana P Index assigns ratings for P loss potential depending on soil properties, topography and land use. These ratings are intended to guide P fertilizer (including animal waste materials) application so as to preserve water quality.
This project has examined measured loss of P in runoff and compared it to P loss ratings calculated using the Louisiana P Index. This was done using small runoff plots and simulated rainfall, consistent with work done elsewhere in the country. Since loss of P from soils enriched in P from years of application of animal waste was the impetus for development of the concept, Louisiana sites included in this study were from the poultry-producing region of the state. Results showed poor correlation between P in runoff and P loss ratings, which was somewhat improved by omitting high P, low P loss ratings data for a grazed pasture. Further insight into P loading into runoff was gained by examining runoff and P concentrations as functions of time. Runoff could often be well-described using the Green-Ampt model for infiltration.
For the forest soil plots examined, however, considerably higher P often appeared in runoff than expected based on soil P desorption, and the source of this P may have been the forest litter layer. Continued difficulties in predicting P loss to runoff based on more mechanistic approaches support use the simpler P Index. However, a better understanding of the mechanisms by which soil P is made subject to runoff loss should lead to improvements in the P Index and better practices for controlling the loss of P to surface water.
| Identifer | oai:union.ndltd.org:LSU/oai:etd.lsu.edu:etd-07092007-182525 |
| Date | 11 July 2007 |
| Creators | Felicien, William Lucas |
| Contributors | Lewis A. Gaston, H. Magdi Selim, Jim J. Wang |
| Publisher | LSU |
| Source Sets | Louisiana State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lsu.edu/docs/available/etd-07092007-182525/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached herein a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to LSU or its agents the non-exclusive license to archive and make accessible, under the conditions specified below and in appropriate University policies, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
Page generated in 0.002 seconds