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Manure Phosphorus and Surface Water Protection III: Transport Factors: Overview Manure Phosphorus (P) and Surface Water Protection III: Transport Factors 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: The importance of agricultural P management to protection of water quality was addressed in Lesson I. Figure 1. Numerous transport processes may be involved in the delivery of P from agricultural lands to surface waters. Factors contributing to P loss from the land to surface waters include source factors and transport factors (Table 1). An interaction of source (Lesson II) and transport factors is needed to have runoff P loss. If either source or transport factors contributes minimally to the risk of P delivery to surface waters, then the risk for P delivery is not likely to be great even if the other set of factors offers much potential for risk. This raises the concept of 'critical source area' (Fig. 1 in Lesson II); the risk is greatest when both the source and transport factors are high. Lesson III addresses the transport factors (Fig. 1). This lesson addresses transport factors that may contribute to P delivery to surface waters. Erosion, runoff, sub-surface flow and drainage, and distance to surface water are the main factors. In some places, wind erosion may be important. The effects of management practices on P transport are discussed. This lesson will describe in detail the water related P transport processes. Objectives: Upon completing this lesson, a student should be able to: 1. Identify transport factors, and analyze their importance, for P delivery to surface waters. 2. Describe the interaction of erosion with soil test P and total soil P relative to P in runoff and erosion. 3. Name and discuss the role of management practices to reduce the effect of transport factors contributing to P loss from a field. Site and management factors Transport factors Soil P levels Runoff P application practices including time, rate and method of application Erosion from rainfall and snowmelt events and from irrigation events Field management practices such as tillage practices and use of cover crops Surface and sub-surface drainage Percolation and under-ground movement of P to seepage areas Distance from P source to concentrated water flow or a water body Stream bank/bed cutting Atmospheric deposition 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).