The Iowa phosphorus (P) index is a risk assessment tool that was developed to assess potential P loss from fields to surface water resources. In 1999, the United States Department of Agriculture Natural Resources Conservation Service (NRCS) issued a national policy and general guidelines on nutrient management to include risk assessments for P These guidelines apply to nutrient management where nutrients are applied with organic by-products and animal manure sources. The national guidelines suggested the use of soil-test P values, threshold limits, or a P risk index. The Iowa State Technical Committee chose the P index approach based on advice from an interdisciplinary task force that involved scientists, technical personnel, and representatives from various interest or commodity groups. All NRCS staff or third-party technical service providers use this guidance when providing financial or technical assistance to producers enrolled in several federal conservation programs. The Iowa legislature mandated the Iowa Department of Natural Resources (IDNR) to begin using the Iowa P Index in late 2003 for manure management plans for confined animal feeding operations. The specific rules and guidelines are being prepared by IDNR at this time. The purpose of this presentation is to provide a brief overview of how the Iowa P index can be used to identify reasons for high risk of P loss from fields and to choose among alternative management practices for improving agronomic and environmental P management.