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Manure Phosphorus and Surface Water Protection IV: Assessment of the Risk of Agricultural P Delivery: Overview Manure Phosphorus (P) and Surface Water Protection IV: Assessment of Risk of Agricultural P Delivery Charles Wortmann Department of Agronomy and Horticulture at University of Nebraska-Lincoln, USA David Tarkalson Department of Agronomy and Horticulture at University of Nebraska-Lincoln, USA Deana Namuth Department of Agronomy and Horticulture at University of Nebraska-Lincoln, USA (http://agronomy.unl.edu) 2005 Lesson Navigation Tips: - Click on 'Animations' button found to the left in order to view the animation which supplements this lesson. You can also click on the animation icon within the text. - Click once on figures to see enlarged versions. - Click once on words in color to bring up their definitions. Overview: Assessment of the potential for P delivery from agricultural land to surface waters is important to development of management plans for reducing P losses to surface waters. The assessment should result in identification of the high risk areas, give a diagnosis of the major causes of P loss, and allow some evaluation of the effectiveness of alternative management practices. This lesson addresses the assessment of potential for P delivery to surface waters resulting from the interaction of the source and transport factors addressed in Lesson II and III. The basic concepts and applications of P indexes as risk assessment tools are explored. Objectives: Upon completing this lesson, a student should be able to: 1. Discuss the "critical source area concept" relative to P delivery to surface waters. 2. Understand and be able to use two P indexes for risk assessment. 3. Determine the effects of different management practices on the estimated risk of P loss from agricultural land. Development of this lesson was supported in part by a University of Nebraska Cooperative Extension grant. A contribution of the University of Nebraska Cooperative Extension, Journal Series _____. Any opinions, findings, conclusions or recommendations expressed in this publication are those of the author(s).