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For more: http://www.extension.org/67754 The inconsistency among P Indices in terms of level of detail and scientific underpinnings among states, as well as in recommendations and interpretations based on site risk, prompted a review and possible revision of the 590 Standard and P-Indexing approach. The need for revision has been heightened by a slower than expected decrease in P-related water quality impairment and, in some cases, an increase in soil P to levels several fold greater than agronomic optimum due to the inability of the P Index to prevent the continued over-application of P to soils. While the basic scientific foundations of the P-Indexing approach are sound, these concerns are real. In this presentation, we propose the use of lower and upper boundaries of P Index use and describe an approach to evaluate individual State P Indices.