ARS | Publication request: Improving our ability to assess risk of phosphorus from agricultural fields

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: April 25, 2011
Publication Date: April 27, 2011
Citation: Bolster, C.H. 2011. Improving our ability to assess risk of phosphorus from agricultural fields. Meeting Abstract. Abstract only.

Technical Abstract: Eutrophication from excess phosphorus (P) loading is widespread among U.S. water bodies with a substantial portion of the P originating from agricultural fields. To reduce the impact agriculture has on water quality, USDA-NRCS includes P-based planning strategies in their 590 Standard to restrict P application to fields where the risk of P loss is high. In the 590 Standard, the most common strategy employed to rate a field’s vulnerability to P loss is the P index. The P index is an assessment tool developed to identify fields which are most vulnerable to P loss by accounting for the major source and transport factors controlling P movement in the environment. USDA-NRCS is currently revising the 590 Standard and may require states to test the accuracy of their P index. In this study the accuracy of the Kentucky P index is evaluated against P-loss data generated from a validated process-based P transport model. Comparing the KY P index with output from a process-based P loss model suggests that in some areas the index does a good job in assigning P risk. However, this analysis also showed some important deficiencies in the index, including the neglect of important factors known to affect P loss and in how the different factors in the index are weighted. To reduce the amount of P that is exported from agricultural fields to waterways within Kentucky, effort and resources should be devoted to updating the KY P index as well as developing long-term monitoring sites where the index and process-based models can be evaluated against measured P loss data.