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P Loss Index as a Guide to Manure Application

P Loss Index as a Guide to Manure Application. Hailin Zhang Department of Plant and Soil Sciences Oklahoma State University. Over applying manure or mismanaging manured fields can cause water quality problems. How does soil P get to water?. Erosion of Particulate P. Infiltration and

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P Loss Index as a Guide to Manure Application

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  1. P Loss Index as a Guide to Manure Application Hailin Zhang Department of Plant and Soil Sciences Oklahoma State University

  2. Over applying manure or mismanaging manured fields can cause water quality problems

  3. How does soil P get to water? Erosion of Particulate P Infiltration and percolation P in Runoff Zone of interaction <2cm

  4. The loss of P in agricultural runoff occurs in: • Sediment-bound (60-90% in cultivated lands) • Dissolved forms (dominated in pasture)

  5. Decisions based on Agronomic Soil Test P alone may inadequately address P related environmental problems. A more comprehensive approach is needed for evaluating specific soils, landscapes, and management system for potential loss of P to water bodies.

  6. P Loss Index Approach Was Introduced in the Early 90’ • Lemunyon and Gilbert. 1993. Concept and need for a phosphorus assessment tool. JPA 6:483-486. • Technical Note. 1994. A phosphorus assessment tool. SCS South National Technical Center. • NRCS Technical Guidance for Developing CNMP. 1999. • States are developing similar systems

  7. What is a P Loss Index • The Phosphorus Loss Index is a field based planning tool that integrates soil properties, hydrology and agricultural management practices to assess the risk of P movement from soil to water

  8. Factors Considered by P Loss Index • Source factors • Soil test P level • Rate and method of P application • Transport factors • Soil erosion and runoff class • Receiving water body sensitivity • P impaired vs. none P impaired watersheds • BMPs • Distance to water bodies • Buffer strips

  9. Critical Source Area High P Source High Transport Critical source areas for P loss from a watershed occur where areas of high soil P and transport potential coincide---Sharpley, et al., 1999

  10. The P Index consists two 4 by 5 matrix. The following are examples of those matrix recommended by the National P Working Group. Some states chose to use different weighting factors or add more components to them.

  11. Example of P Source Factors

  12. Example of P Transport Factors

  13. Interpretation of the P Loss Index Manure application rate may be limited if PI is high, BMPs may be required

  14. Research Needs • To calibrate weighing factors and validate P loss Index • Evaluate BMPs for those fields already high in P • ????

  15. What System is Good for Oklahoma? • Pasture vs. Row crops • Precipitation differences • Soil pH differences • Soil Test P <120 vs. STP>120 • Water soluble P

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