The Science Behind the Phosphorus Risk Index

1. The Science Behind the Phosphorus Risk IndexWes Jarrell, Professor and HeadNatural Resources and Environmental Sciences, UIUC March 2, 2005

2. EPA proposed Total P criteria for Upper Midwest water bodies -from Robertson et al.

3. Readilybioavailable ? Forms of P - % of total Seasonably bioavailable Water Menomonee R, Armstrong Soil 0.04% 15% 60% 25% Dissolved (PO4) 30% 3% 27% 40% e.g.,Bray Sorbed Insoluble/ inorganic Ca, Fe, Al -P ? Organic TP= 500 mg P/L TP =0.138 mg P/L

4. Load vs concentration Instantly bioavailable: dissolved PO4 and desorbable PO4 Seasonally bioavailable P: P in organic or inorganic particles that is released over a growing season

5. Sources of water to water body • Runoff - main source of P load • Direct precipitation inputs • Baseflow - seepage from groundwater: • Wisconsin: 10 - 50 ppb total P • Higher concentrations in some areas • Point sources - discharges from municipal-industrial sources

6. P Transport – Land to WaterNonpoint sources Precipitation Particles – Entrainment Dissolved Dissolution Sorption/Desorption Settling - enrichment Receiving water Settling - enrichment Field Concentrated flow Delivery zone Rusle2Bray vs totalBray vs solubleSoluble P in fert. Sedimentdelivery ratioBuffer effectiveness

7. SUMMARY Phosphorus that could cause problems in water occurs both in particles (PP) and dissolved in solution (SP) when it reaches surface water. We consider both particles and dissolved P.

8. Phosphorus Transport - Land to Water LEVEL OF DETAIL USER PI-EZ Land/water/animal manager P index/ Rusle2 APEX - field/farm PALM - field/watershed Researcher SWAT - watershed

9. Desirable Characteristics of P index • Accurately rank fields in order of their risk of supplying P to a water body • Based on best available science, easily modified to reflect improvements • Easy to use, interpret, and apply • Helps user understand factors affecting P movement to water • Direct user to improved management practices that effectively and economically lower the risk • Should be applied over the whole farm • Provide maximum flexibility to farmer, while decreasing P loading.

10. Total Risk Index for Phosphorus (PI): PI = PP + SP + LP PI = Total P index PP = Particulate P SP = Soluble P LP = Leached P

11. Total P in soils and clays, native soils, Wisconsin (Boerth and Helmke, 1997)

12. Average P concentration in particulates, mg P/kg 0 1,000 2,000 3,000 4,000 5,000 Wisconsin soils (Boerth and Helmke) Wisconsin soil clays (Boerth and Helmke) Runoff plot sediment (Bundy and Andraski) Small Wisconsin streams (Baum, WDNR) Wisconsin streams (Corsi et al., USGS) Living algal cell or crop plant leaf To 11,000+ Soil organic matter Manure Scenescent leaf Modeling land use effects (Panuska, others, WDNR)

13. PP: Depends on (1) erosion, (2) fraction of eroded particles delivered to stream, and (3) P concentration in the soil particles Calculation: Particulate P = Rusle2 * Sediment Delivery Ratio * Enrichment Ratio * BufferEffectiveness* Soil particle P concentration (from Bray P1)

14. Also: Meyer, Lyne, Avila, Barak, UW Madison, Plano silt loam: Total P = 2.5 (Bray P1) + 875

15. “It appears that most of the sediment generated by a particulate erosion event is usually deposited in small or headwater tributaries.”- Glymph and Storey, 1967

16. Sediment Delivery RatioS = SY0 e –bT (D)1/2WhereS = sediment yield at the down stream channel outlet,SY0 = sediment yield at the upstream end of the channel,b= (Beta) decay constant or routing coefficient,T = Travel time through the section in hours,D = the particle diameter in millimeters.FromJohn Panuska – J.R. Williams original model

17. Soluble P: Depends on amount of runoff, P concentration in the soil, and soluble P concentrations in P-containing amendments/fertilizers Total soluble P = SP from soil P + SP from unincorporated nutrients on unfrozen soil + SP from unincorporated nutrients on frozen soil ( + SP release from crop residues?)

18. P concentration in solution, mg/L 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 Lower target for wastewater discharge (total ) Soil solution [P] at 50 ppm Bray P-1 Lower limit for maximum crop growth in soil (soluble) Lower limit for eutrophic lake (total) Upper limit for oligotrophic lake (total) Manure: 10 - 30 mg P/L (100:1 dilution) Upper limit for oligotrophic stream (total)

19. Soluble P load in runoff: • For no fertilizer or incorporated fertilizer: • Soil solution equilibrium [P] (from Bray P1) * • Annual runoff volume (from Rusle2)

20. Bundy and Andraski

21. Soluble P load in runoff – • For surface-applied nutrients without incorporation: • Soluble P in manure/fertilizer (lb/A) / • average days between runoff-generating events

22. Soluble P load in runoff – cont’d • Soluble P in manure

23. 4 “ Rainfall 2000 Runoff Events 2000 N-S Chisel Plow Runoff Events 2000 Runoff event frequency Arlington, Wisconsin PALM output, Norman et al. Contour Ridge Till

24. Soluble P in runoff from frozen soil – • For snow-melt events with nutrients spread on frozen soil: • Soluble P in manure (lb/acre)* • Slope percentage(squared)/200

25. **NOT YET INCORPORATED INTO MODEL** • Soluble P load from crop residues • For loss from crop residue • SP = f(Soluble P in residue, • spring runoff volume, ??)

26. **NOT YET INCORPORATED INTO MODEL** LP = P lost through leaching, especially to tile lines LP = f(P concentration in soil solution, depth to tile, retention coefficient, recharge volume)

28. P index values for one field: Corn, 4% slope, 300 ppm Bray P1, 50% sol P in manure

29. Export coefficients – Model Panuska et al., WDNR

30. Preliminary Interpretation of risk associated with PI values: 0 – 2 Low risk: low probability of being a problem except for very sensitive water bodies 2 – 6 Intermediate risk: important for water bodies sensitive to P inputs 6 - 10 High risk: Likely excessive in most watersheds >10 Very high risk: Excessive for almost any water body

31. The Phosphorus Risk Index -Progressive Planning Case 1 - degradation Phosphorus Risk Index Case 2 - balance Case 3 - restoration 1 2 3 4 5 6 7 Years

32. The framework of the PI is in place. • Now it needs • ADAPTATION to specific regional conditions in Wisconsin; • EVALUATION at a variety of scales, to see if it truly measures what we intend it to measure; • USABILITY for planners and plan implementers; • COMPARISON with other states

33. Summary • The PI should be part of a Systems Approach to Phosphorus Management in Wisconsin Agriculture • It provides a framework into which we can incorporate the best existing science and extend it to users • The PI should complement and be consistent with other models • Gaps in our understanding of the system are identified through applying the PI • Adaptation, Evaluation, Usability, and Comparability are needed to apply the PI more efficiently

35. Forms of Phosphorus in Water and Their Bioavailability Wes Jarrell, Senior Scientist Discovery Farms Program

36. "A river and its plankton are a flowing soil and its crop,...." (p. 147). Forbes, S. A. and R. E. Richardson. 1919. Some recent changes in Illinois River Biology. Bull. Ill. State Natural History Survey 13:141-156. (Thanks to Erwin Van Nieuwenhuyse, CA)

37. Corollary: "A soil is benthic sediment in an intermittent stream supporting emergent vegetation.” W.M. Jarrell, 2000, and likely someone else, circa 1940.

38. “It has been suggested that God must have been a limnologist or an oceanographer …” Harris, Phytoplankton Ecology, 1986

39. Regulations will be based on Total P in water; we have no easy ways of determining bioavailable P in the particle fraction Total P (mg P/L) = Particulate P (PP) + SRP

40. Loads Total P: All P in particles and all dissolved P entering water body Bioavailable P: Phosphorus that is, or can rapidly become, the PO4 (ortho-P) form; from 10 to 90+% of total P

41. Follow the colloids! Colloid: - Particle less than 2 mm in diameter (clays, organic matter) - Settles out of water very slowly - High surface to volume ratio - Often high concentrations of nutrients

42. Total P (mg P/L) = Particulate P (PP) + SRP Total P in water is comprised of (1) Particulate P, which does NOT pass through the 0.45 mm filter, and (2) P that passes through a 0.45 mm filter, also called “dissolved P”, “soluble reactive P” (SRP), “ortho-P”, “soluble P” (reminder: colloids at usually <2mm)

43. Actual analyses Total P: strong acid dissolution of entire water sample, determine ortho-P in digest. SRP: direct determination of water passing through a 0.45 mm filter

44. SRP - Immediately bioavailable - Where did it come from? - How can we control it? Units ppb: mg/L (for water), mg /kg (particles, soil); or ppm: mg/L (for water) or mg/kg (particles, soils)

45. Minimum solution concentrations from which plants can extract P in flowing solution: Algae: 0.3 - 0.6 - 1 mg P/L (ppb), 0.001 ppm Rye: 3 mg P/L (ppb), 0.003 ppm Oats: 7 mg P/L (ppb), 0.007 ppm

46. Bioavailability Critical P concentrations and trophic state in water Periphyton streams (low flow) Trophic state Total P mg P/L Eutrophic 0.020

47. Bundy and Andraski

48. PARTICULATE PHOSPHORUS - Particulate P (PP) in water is organics, aluminum, iron, and calcium phosphates - How much PP is bioavailable in a given situation? - Where did it come from? - How can we control it?

49. To estimate average P concentration in suspended particles in water: (1) Calculate Particulate [P]: PP(mg P/L) = TP - SRP (2) Divide PP concentration by TSS concentration: (Total suspended solids (TSS) in water: mg solids/L) PP (mg P/L) TSS (mg solids/L) mg P mg solids P concentration in suspended solids = =

50. P concentrations in water particulates