Nelson, Nathan O.Shober, Amy L.2013-03-042013-03-042013-03-04http://hdl.handle.net/2097/15333Citation: Nelson, N.O. and Shober, A.L. (2012), Evaluation of Phosphorus Indices after Twenty Years of Science and Development. J. Environ. Qual., 41: 1703-1710. doi:10.2134/jeq2012.0342The P Index was proposed as a nutrient management tool in 1992 and has been implemented as such for the past decade. However, lack of water quality improvement in agricultural watersheds and discrepancies in P loss ratings between P indices have raised questions about continued use of the P Index. In response to these concerns, a symposium was held as part of the 2011 ASA, CSSA, SSSA annual meetings. This symposium produced a special collection of seven papers describing the role of P indices in P management, evaluation of P indices, new models for assessing P loss, methods to improve P indices, and changes in producer behavior resulting from P Index use. The objectives of this introductory paper are to provide background on the P Index concept, overviews of the special collection papers, and recommendations for future P Index evaluation and development research. The papers in this special collection conclude that P indices can provide accurate assessments of P loss but must be evaluated appropriately. Evaluation will require compiling large regional P loss datasets at field and small watershed scales. Simulation models may be used to generate P loss estimates; however, models must be calibrated and validated to ensure their accuracy. Further development of P indices will require coordinated regional efforts to identify common P Index frameworks and standardized interpretations. Stringent P Index evaluations will expand the utility of P indices for critical source area identification and strategic best management practice implementation by regulatory, education, and scientific communities alike.en-USPublished article is Open Access. This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).PhosphorusP IndexArticle (publisher version)