title: Evaluation of phosphorus indices after twenty years of science and development.
abstract: The 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.
authors.affiliation: Department of Agronomy, Kansas State University, Manhattan, KS, USA. nonelson@ksu.edu
authors.forename: Nathan O
authors.initials: NO
authors.lastname: Nelson
authors.forename: Amy L
authors.initials: AL
authors.lastname: Shober
mesh_terms: D000818:Animals; D003247:Conservation of Natural Resources; D004784:Environmental Monitoring / Q000379:methods*; D004785:Environmental Pollutants / Q000737:chemistry*; D010758:Phosphorus / Q000737:chemistry*; D012106:Research
chemical_list: D004785:Environmental Pollutants; D010758:Phosphorus