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Tools for phosphorus management

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For more: http://www.extension.org/67754 The inconsistency among P Indices in terms of level of detail and scientific underpinnings among states, as well as in recommendations and interpretations based on site risk, prompted a review and possible revision of the 590 Standard and P-Indexing approach. The need for revision has been heightened by a slower than expected decrease in P-related water quality impairment and, in some cases, an increase in soil P to levels several fold greater than agronomic optimum due to the inability of the P Index to prevent the continued over-application of P to soils. While the basic scientific foundations of the P-Indexing approach are sound, these concerns are real. In this presentation, we propose the use of lower and upper boundaries of P Index use and describe an approach to evaluate individual State P Indices.

Publié dans : Formation, Technologie
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Tools for phosphorus management

  1. 1. Tools for PhosphorusManagementAndrew SharpleyWater to Worth: Spreading Science and SolutionsDenver, CO; April 1 – 5, 2013
  2. 2. History risk assessmentRevision of the NRCS 590 NutrientManagement Standard & P IndicesIts use & misuse for P managementBMPs and their assessmentThe way forwardToday’s presentation
  3. 3. ARSLand Grant
  4. 4. • National P Research Project outcomes Standardized methods for rainfall – runoff studies Established relationships between STP and runoff Integrated into P Indices Incorporated into NMP process• Success partly due to Group effort – Land Grant & ARS Flexibility to adapt to State needs
  5. 5. ..it was mobile
  6. 6. Arkansas
  7. 7. Illinois
  8. 8. Virginia
  9. 9. New York
  10. 10. Outreach
  11. 11. Dissolved Pmg L-1Mehlich-3 P, mg kg-1FD-36 watershed - PA10230 200 400 600 800R2 = 0.86Crop response200 mg L-1Change point
  12. 12. P loss affected bymany factors1771444446201<19755DP8DP78920Tony Buda, ARS, PASoil P – ppmP added – kg P/ha/yrRunoff – litersP loss – kg P/ha/yr
  13. 13. HighsourceHightransportCritical Source AreaLed to the 80/20 rule:80% of P comes from20% of land areaRisk assessment used by most states fornutrient management planning (CPS 590)
  14. 14. • Runoff potential• Erosion potential• Leaching potential• Proximity to streamTransportSource• Soil P content• Added P• Rate, method, timingof fertilizer & manure• Manure P solubility
  15. 15. 1023P index value for the site0 50 100 150 200R2=0.8075 kg P/ha TSP112 kg P/hapoultry litter150 kg P/hapoultry manureRunoff P,g/haVery highHighMedLowSoil P, mg/kg
  16. 16. P loss is controlled by many factors
  17. 17. • Disparity among Indices across the country Varied with soils, topography, & state priorities• Often, not leading to a decline in STP norimprovement in water quality Legacy effects• Perceived as farmer friendly• The P Index was never meant to be thesolution to P management issues
  18. 18. P losskg ha-1AL AR GA MS NC TN TX0.5 Low Low Low Low Low High Med.2.7 Med. High High Low Low V. High High4.0 Low High Med. Low Low V. high High5.8 Low V. high V. high Low Med. V. high High10.9 Low V. high V. high Low Med. V. high High23.7 Low V. high V. high Low High V. high HighOsmond et al., 2012
  19. 19. • Appropriately account for major sources& processes determining P loss & rank riskof loss for any given site• Directionally and magnitudinally correct• Interpretations based on assigned risk areequivalent across state borders, givensimilar site & water resource conditions• Where inadequacies exist, the causes canbe identified & addressed
  20. 20. •At a minimum this should include Site runoff, management, climate,water quality Event, planning / rotation period &annual loss Natural rainfall• Network of sites and data exchangebeing developed – Kleinman et al.• MANAGE – Daren Harmel
  21. 21. •Select appropriate model APEX, APLE, DrainMod Locally calibrated (within state) Event, planning / rotation period &annual loss• Model & Index must estimate P loss &simulate P mobilization & transportover same time scales
  22. 22. Dietary P mgt. & useof enzymes enhancesnutrient absorption &reduces excretionManure additivescan reduce Psolubility & NH3 lossManure treatmentSolid-liquidseparation, struvite,zeoliteStruvite
  23. 23. Subsurface injectionreduces P runoff & NvolatilizationSoil & manuretestingto tailor ratesof P to apply4 R’sAppropriate rate, methodtiming, & placementof P can increase cropuptake & decrease runoffloss
  24. 24. Rotational grazingreduces P runoff & NleachedStream bankfencingDecreases Pdeposition instreamsConservationtillagereduces P runoffRiparian bufferstrap particulatenutrientsCover cropsreduces P runoff
  25. 25. BMP CreditDiversion 5%Terrace 10%Pond 20%Fenced Pond 30%Filter Strip 20%Fenced Filter Strip 30%Grassed waterway 10%
  26. 26. BMP CreditFencing 30%Riparian Forest Buffer 20%Fenced Riparian Forest Buffer 35%Riparian Herbaceous Cover 20%Fenced Riparian Herbaceous Cover 30%Field Borders 10%
  27. 27. -100 1000Effect on total P loss, %Decreased loss Increased lossManure mgt. system (14)Nutrient mgt. plan (14)Stream fencing (3)Vegetated buffers (34)Dinnes et al., 2004 & Gitau, 2005-40%-15%Farm pond (12)-50%-28%-65%
  28. 28. AR Water Resources Center, 2012Dissolved P Total P2000 0.224 0.3772003 0.148 0.2442011 0.070 0.130Mean annual concentration, ppm
  29. 29. Maumee RiverwatershedSandusky RiverwatershedMICHIGANLake ErieOHIOLessons from Lake Erie Basin
  30. 30. Annual flow-weighted total P, ppm1975 1985 1995 20050.80.60.400.250% decreaseDave Baker & Peter Richards, OH
  31. 31. Adoption of mulch and no-till soybeans, %1975 1985 1995 20050.120.090.0600.03Annual flow-weighted dissolved P, ppm75% decrease80604020
  32. 32. 1975 1985 1995 20050.120.090.0600.03Adaptive management mayhave reduced nutrient loss Incorporation of fertilizer andmanure Winter cover crops Spring fertilization
  33. 33. • Spring workload is huge with moretime-sensitive tasks• Fertilizer usually costs more in spring• Less soil compaction on frozen groundBut the reality is …….
  34. 34. • Researchers need tostep back and lookat the big picture

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