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My Field has High Soil Test P. Now what?

My Field has High Soil Test P. Now what?. John A. Lory, Ph.D. Division of Plant Sciences Commercial Agriculture Program University of Missouri. P Assessment Scale Field. Nutrient Management Scale Farm. Water Quality Scale Watershed. P Assessment Scale Field. Nutrient Management

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My Field has High Soil Test P. Now what?

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  1. My Field has High Soil Test P. Now what? John A. Lory, Ph.D. Division of Plant Sciences Commercial Agriculture Program University of Missouri

  2. P Assessment Scale Field Nutrient Management Scale Farm

  3. Water Quality Scale Watershed

  4. P Assessment Scale Field Nutrient Management Scale Farm Water Quality Scale Watershed

  5. Lake 3 – MU Dairy Farm Lake: 6 acres Watershed: 77 acres Mean soil test P: 94 lbs/a 197 ppb P

  6. Missouri Reservoirs Missouri reservoirs Water Clarity as measured by Secchi depth (m) Lake 3 Jones and Knowlton 1993

  7. Lake 1 – MU Dairy Farm Lake: 15 acres Watershed: 135 acres Mean soil test P: 69 lbs/a 223 ppb P

  8. Lake 2 – MU Dairy Farm Lake: 2.4 acres Watershed: 22 acres Mean soil test P: 91 lbs/a Lake 2 68 ppb P

  9. Understanding Edge of field P losses

  10. Effect of soil test P on runoff P in forage systems (small plot runoff) Creldon Soil Dissolved Reactive P in runoff (ppb) Bray-1 Soil Test P (lbs/acre)

  11. What are my options? 223 ppb P

  12. What are my options? Improve timing of application 223 ppb P

  13. Improve timing of surface application 200 lbs./acre phosphate applied 3/22/00 to forages Water Soluble P in Runoff (ppm) Days After Treatment Mt. Vernon, MO

  14. Effect of recently applied P on runoff P in forage systems DAP Poultry Litter Dissolved Reactive P (mg kg-1) Days after application

  15. Soil moisture at Mt. Vernon, MO 2003 Saturated soil Volumetric Water Content (%) 2 inches 4 inches Precipitation (in) Nov. Jan. Feb. Mar. Apr. May Jun. Jul. Aug. Sep. Oct. Dec.

  16. Soil moisture at Mt. Vernon, MO 2004 Saturated soil Volumetric Water Content (%) 2 inches 4 inches Precipitation (in) Nov. Jan. Feb. Mar. Apr. May Jun. Jul. Aug. Sep. Oct. Dec.

  17. Nitrogen for Tall Fescue Hay Forage yield Herd feed requirement April June August October

  18. Litter is an excellent fertilizer for fall fescue growth

  19. What are my options? Lower P index on fields 223 ppb P

  20. The importance of erosion

  21. What are my options? Lower P balance watershed Export more manure Import less manure and fertilizer 223 ppb P

  22. What are my options? Lower P balance watershed Should I raise STP on this field? 223 ppb P

  23. Raise soil test P 10 units with manure • Low testing field: 5 ppm to 15 ppm • Very high testing field: 50 to 60 ppm • Very high testing field: 500 to 510 ppm Is there a water quality benefit from choosing one field over another?

  24. Raise soil test P 10 units with manure • Low testing field: 5 ppm to 15 ppm • Improved yield and forage quality • Reduced erosion • Lower runoff volume • Very high testing field: 50 to 60 ppm • Very high testing field: 500 to 510 ppm

  25. What are my options? Follow the rules. No application on frozen or saturated soils No application on >10% slope Adhere to setback requirements 223 ppb P

  26. What are my options • Improve timing of applications • Lower field P index • Import less and export more P • Follow the rules

  27. Some philosophy • It is a lot easier to avoid a problem then to fix a problem. • The P index is best used as a educational tool, not a justification for more manure applications

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