1. Iowa P-Index Relationship to Feedlots Steve Brinkman CCA Nutrient Management Specialist USDA / NRCS steven.brinkman@ia.usda.gov 515-323-2243

2. Why!!! 300 head finishing Cattle open lot 4 ton / head /year 1200 tons / year produced Manure analysis Total N – 14 # / ton P2O5 -- 11 # / ton 16800# Nitrogen- 13200# P2O5

3. Why!!! 35% N availability 30% application loss 100% P availability 156 bu corn 44 bu beans 125# N 36.4 ton Nitrogen Rate =33 acres + 33 acres = 66 acres 8.5 ton P- removal rate = 141.2 acres + 141.2 acres = 282.4 acres

4. Purpose of the P-Index Assess the Risk of Phosphorous delivery to surface waters Tool to be used by Conservation Planners, Landowners and Land Users Used to Help Make Management Decisions in Developing ways to Reduce Risks

5. Iowa Phosphorus Index Tool to assess potential for P loss from field to surface water More comprehensive than soil test Integrates many soil and field characteristics Integrates many management and conservation practices P-Index looks at source and transport factors

6. When is the P-Index Required NPDES – NMP’s > 1000 animal units found to have discharged and need a permit or declared a CAFO DNR – MMP Confinement feeding operations over 500 animal units

7. When is the P-Index Required EQIP funds are used for waste water and manure handling needs NRCS -- CNMP NRCS – NMP’s if

8. P-Index Use Required -- NRCS Animal Manure or Organic By-Products applied ID as designated P related impairment (DNR 303D List) http://www.iowadnr.com/water/tmdlwqa/wqa/3 03d.html Current Soil Test P is very high Soil Losses exceed T

9. Phosphorus Index Characteristics ¨ Source Factors soil test P, (STP) total P, rate, methods, and timing of P applications (including manure), erosion

10. Phosphorus Index Characteristics ¨ Transport Factors sediment delivery, relative field location in watershed, soil conservation practices, precipitation, runoff, tile flow/subsurface drainage

11. P-Index -Three Components Erosion Component Runoff Component Subsurface Drainage Component

12. Erosion Component ¨ (Gross Erosion X Sediment Trap) X (Sediment Delivery X Buffer) X Enrichment Factor X Soil Test Phosphorus Erosion Factor ¨ Erosion factor considers sheet and rill erosion, sediment trapped by conservation practices sediment delivery rates, enrichment, STP, and buffers

13. Runoff Component ¨ Runoff Curve Number Factor X Precipitation Factor X STP Runoff Factor ¨ Runoff Factors considers water runoff based on a modification of the runoff curve number, STP which includes rate, method, and timing of P applications

14. Subsurface Drainage Component ¨ Flow Factor (Tile or Subsurface Flux) X Precipitation Factor X STP Subsurface Transport Factor ¨ Surface Transport Factor considers the presence of tiles and index of water flow through the soil profile, STP, and precipitation

15. Looking Into the Erosion Component Total Gross soil erosion Estimated by RUSLE2 adding ephemeral and classical gullies Modified by : sediment trap and sediment delivery Filter strip factor Sediment enrichment factor Total soil P factor

16. RUSLE2 Make sure to use the Appropriate Dominant Critical Area for the P-index when Running RUSLE2 sheet and rill erosion. Should the P-Index be applied to whole fields, or portions of a field? Depends!!! Research has shown that the majority of our P runoff comes from a few of the acres in a field. So why not plan a higher level of conservation to the area of a field that shows to have the greatest risk. The P-Index can also be used as a decision tool when managing a field.

17. Dominant Critical Area Phosphorus Index: Iowa NRCS Technical Note 29 is to be used when determining dominant critical area. Small, insignificant SMU areas of 10% or less of the field are not to be used. However, since small areas are known to contribute significant phosphorus loss within a field, areas greater than 10% are to be considered when determining the soil loss for input into the P-Index since this is a resource concern. When determining this dominant critical area look at the most erosive area that is greater than 10%. To determine this area, use the following process:

18. Dominant Critical Area Consider first the SMU that is > 10% for the Dominant Critical Area. If critical area consists of several SMUs that are 10%. (i.e. 120D2, 20D2) If the sum is > 10% use the one with the largest percentage for calculating the PI. If the sum is < 10% then it is not the dominant critical area If the sum of the SMU with like slope classes is > 10% and have different erosion phases use the erosion phase with the highest percentage (i.e. 10%-120D2 and 4%-120D3 use 120D2).

22. Erosion Component Value 0.00 Gross Erosion (tons/acre) Sheet & Rill (RUSLE2) Area (ac)Tons Ephemeral0.0 Gully0.0 Factor0.0

26. Recommendations for Types of Manure in RUSLE2 Database: Iowa NRCS web site RUSLE2 Manure pdf ftp://ftp- fc.sc.egov.usda.gov/IA/technical/RUSLE2Ma nure.pdf

27. Recommendations for Types of Manure in RUSLE2 Database: “Manure, liquid” (swine from confinement, holding ponds and municipal sewage): use Equation A, “Manure, semi-solids” (includes beef, swine and dairy settling basin): Use Equation A “Manure, open lots” (beef, swine, dairy manure from open lots and buildings and poultry manure): Use Equation B, solids “Manure, with bedding” (horse, sheep packs including straw and shredded newspaper): Use Equation C

28. Recommendations for Types of Manure in RUSLE2 Database: Equation for semi-solids (lbs /ac) X (% semi-solids as a decimal) = lbs dry matter Sample calculations: (15000 lbs /ac) X (0.55) = 8250 lbs/ac dry matter RUSLE2 Conversion: 8250 lbs/ac dry matter X 0.5 = 4125 lbs/ac

29. Ephemeral Gully Erosion Definitions Ephemeral Erosion---- concentrated flow areas of erosion that can typically be filled by tillage equipment Classical Gully Erosion---- concentrated flow areas of erosion that need earth moving equipment to be repaired

30. Classic Gully

31. Ephemeral Erosion

32. Length 100ft Top width 1ft Bottom width 0.5 ft Depth 1ft Sandy loam soil 105# / cu ft 3.94 ton soil Example

33. B C Drawing Not To Scale D Ephemeral Gulley Erosion A A = Top Width in Feet B = Bottom Width in Feet C = Depth in Feet D = Length in Feet E = Soil Unit Weight* H = Number of Years * Sands, Loamy sands, Sandy loams Fine sandy loam = 105 Lb/ft 3 * Loams, Sandy clay loams, Sandy clay, Silt loam, Silty clay loam, Silty clay, & Clay = 85 Lb/ft 3 (A + B) x C x D x E = Tons/ Year 2 x 2000 x H

34. B C Drawing Not To Scale D Ephemeral Gulley Erosion A A = Top Width in FeetA = 1’ B = Bottom Width in FeetB = 0.5’ C = Depth in FeetC = 1’ D = Length in FeetD = 650’ E = Soil Unit Weight*E = 85 Lb/ft 3 H = Number of YearsH = 1 * Sands, Loamy sands, Sandy loams Fine sandy loam = 105 Lb/ft 3 * Loams, Sandy clay loams, Sandy clay, Silt loam, Silty clay loam, Silty clay, & Clay = 85 Lb/ft 3 (A + B) x C x D x E = Tons/year 2 x 2000 x H (1 + 0.5) x 1 x 650 x 85 = 20.72 Tons/year 2 x 2000 x 1

35. Gross Erosion (tons/acre) Sheet & Rill (RUSLE2)3.9Area (ac)Tons Ephemeral0.6139.350.0 Gully0.0139.30.0 Factor5.6 From RUSLE2 Total area Of Field Use ephemeral Equation from Previous slide

38. Questions??