1. Phosphorus Index Based Management Douglas Beegle Dept. of Crop and Soil Sciences Penn State University dbb@psu.edu http://panutrientmgmt.cas.psu.edu

2. Why do we need a P Index? Why not just agronomic recommendations? NP2O5P2O5 K2OK2O Nitrogen Based Corn/Dairy Manure Regional P Balance ¼ ¾ Manure Crops Soil Animals Feed Eutrophication Nutrient flows in modern ag P Index ? Field P Balance NP2O5P2O5 K2OK2O Phosphorus Based Corn/Dairy Manure P Index

3. SourceTransport Critical Source Area P Index Critical Source Area Management Overlap of Source & Transport Indicators Identify and manage the critical source areas Evaluate environmental risk Target effort and resources

4. Critical Areas of P Export 90% of annual P export comes from 10% of land area Mahantango Creek Watershed, USDA-ARS 90% of P Loss comes from 10% of the watershed

5. Managing Phosphorus Pollution Subsurface flow Tile flow Leaching Sources Transport Erosion Runoff N P K Hydrology Water Body

6. Mehlich-3 soil P, mg/kg 0 200400600800 P loss, lb P 2 O 5 /A Soil Test vs P Loss R 2 =0.80 0.8 0 1.62.4 Sharpley, USDA-ARS Crop P Optimum P Threshold No recent P inputs

7. Managing Phosphorus Pollution Subsurface flow Tile flow Leaching Sources Transport Erosion Runoff Hydrology Water Body N P K

8. Mehlich-3 soil P, mg/kg 0 200400600800 P loss, lb P 2 O 5 /A 75 kg P/ha TSP 112 kg P/ha swine slurry 150 kg P/ha poultry manure 75 kg P/ha TSP 112 kg P/ha swine slurry 150 kg P/ha poultry manure Soil Test vs P Loss - with applied P Soil Only R 2 =0.80 For all data points R 2 =0.40 0.8 0 1.62.4 Sharpley, USDA-ARS

9. Phosphorus Index P Source Site Characteristics –Environmental Soil Test P Same soil test different interpretation Sampling Questions? P Saturation? –P Fertilizer Rate and Appl. Method –Organic P Rate and Appl. Method P Source Coefficient (PSC) –Direct availability of manure P to runoff –Based on WEP in manure

10. Managing Phosphorus Pollution Subsurface flow Tile flow Leaching Sources Transport Runoff N P K Hydrology Water Body Erosion

11. Phosphorus Transport by Erosion Erosion reduced 95% 198019851990 1995 Conventional till wheat Converted to no-till Total P mg/L 6 4 2 0 - - Sharpley, USDA-ARS

12. Managing Phosphorus Pollution Subsurface flow Tile flow Leaching Sources Transport Erosion N P K Hydrology Water Body Runoff

13. Zone of Interaction with Runoff 100 0 100 200 300 400 500 600 0 20 40 60 80 Mehlich 1 P (mg/kg) Depth (cm) Data from Mozaffari and Sims, 1994 Zone of interaction with runoff Plow depth  Location of applied P  Interaction with runoff P on surface Soil test at surface High P Saturation at surface P sat = P / Al + Fe Oxalate extr. or Mehlich 3 extr.

14. Soluble P Transport in Runoff Conventional till wheat 1980 1985 1995 1990 Algal-available P, mg/L 0.5 1.0 0 Converted to no-till Sharpley, USDA-ARS

15. Managing Phosphorus Pollution Subsurface flow Tile flow Sources Transport Erosion Runoff N P K Hydrology Water Body Leaching

16. Soluble P Loss by Sub-surface flow Very Dependent on soil properties –Hydrology Piston flow Macro pores –Texture –Soil Chemistry (Fe, Al, Ca) –P loading/saturation –Artificial Drainage Data from: Bolton et al., 1970 Culley and Bolton, 1983

17. P Loss is a Complex “Landscape” Process Subsurface flow Tile flow Leaching Sources Transport Erosion Runoff N P K Hydrology Water Body

18. Modified Connectivity: Direct Connection Landscape Transport Modified Connectivity: Riparian Buffer Distance Runoff Return Period Hydrology

19. Phosphorus Index P Transport Site Characteristics –Soil Erosion –Runoff Class –Leaching Potential Sub-surface Drainage –Contributing Distance –Modified Connectivity Erosion Runoff Drainage Distance

20. PA Phosphorus Index v 2.0

21. 0.4 0 0.81.2 P loss, kg/ha P index value for the site 0 50100150200 75 kg P/ha TSP 112 kg P/ha swine slurry 150 kg P/ha poultry manure 75 kg P/ha TSP 112 kg P/ha swine slurry 150 kg P/ha poultry manure P Index describes P loss potential Very high High MediumLow Sharpley, USDA-ARS R 2 =0.79

22. Phosphorus Index Low P Index –N Based Management Medium P Index –N Based Management High P Index* –P Based: Crop removal Very High P Index* –No P: Manure or Fertilizer High and Very High* –Modify Management based on P No or reduced manure Change time or method of application Conservation practices Buffers Etc.

23. Phosphorus Nutrient Management Plan Develop N based plan –Usually means excess P will be applied Use P Index to evaluate the N based plan –Is the risk of P loss acceptable Acceptable risk –Apply @ N rate, excess P Unacceptable Risk –Modify N based plan, where necessary, to address P loss risk NP2O5P2O5 K2OK2O Nitrogen Based Corn/Dairy Manure NP2O5P2O5 K2OK2O Phosphorus Based Corn/Dairy Manure or

24. P Index Application Eventually, all fields will have a high P index P Index is not the solution –Tool to buy time to solve problem –Minimizes negative impact of P while we come up with a sustainable solution –We need to get the system into better balance

25. NRCS/EPA P Index Issues Proposed change in NRCS 590 Std. –P soil test only – No more P Index Easy to regulate Very strict limits Not supported by the science - Source/Transport Unrealistic for animal agriculture to comply with in short term Better soil P balance is a good long term goal –Withdrawn, under further review

26. College of Agricultural Sciences Department of Crop and Soil Sciences