for Watershed Planning Laura Ward Good UW-Madison Soil Science Department February 8, 2011

Transcription

1 Wisconsin P Index Basics for Watershed Planning Laura Ward Good UW-Madison Soil Science Department February 8, 2011

2 Wisconsin P Index Basics for Watershed Planning What it is What makes it change How it varies across watersheds

3 Wisconsin P Index Calculated P lb/acre/year delivered with average weather Dissolved P soil Dissolved P manure/fertilizer Eroded sediment P Field Stream

4 County Soil Type Soil Test P and Organic Matter Rotation Average WI P Index Field Slope Field Slope Length Tillage Rotation oa o crops copsand yields Manure Applications P Fertilizer Applications Downfield Slope to Surface Water Distance to Surface Water Phosphorus Index County Relative indicator of the potential for runoff Pfromagivenfieldto field contaminate surface water (lbs P/ac/yr)

5 Phosphorus h Index Equations Dissolved P from soil Dissolved P from manure and fertilizer Eroded sediment P [P] x Transport = P delivered

6 County Soil Type Soil Test P and Organic Matter Field Slope Field Slope Length Available P on Field Surface Soil total P Soil soluble P Tillage Rotation oa o crops copsa and yields Manure Applications P Fertilizer Applications Downfield Slope to Surface Water Distance to Surface Water Manure & fertilizer soluble P

7 Field Transport Potential County Soil Type Soil Test P and Organic Matter Weather databases Erosion - RUSLE2 Field Slope Field Slope Length Tillage Rotation crops and yields Manure Applications P Fertilizer Applications Downfield Slope to Surface Water Distance to Surface Water Rainfall runoff Frozen soil runoff

8 County Soil Type Soil Test P and Organic Matter Field Slope Field Slope Length WI P Index Calculations for Nutrient Management Planning Field is uniform Dominant critical soil, slope, and slope length High erosion estimate Tillage Rotation crops and yields Manure Applications P Fertilizer Applications Field

9 Fields lose P with runoff and erosion Average winter (W, frozen soil) and nonwinter (NW) runoff, sediment and phosphorus loss for monitored fields and pastures, Runoff inch Sediment T/a ton/acre inch Phosphorus lb/a lb b/acre W NW W NW W NW W NW Dissolved Particulate

10 Testing Source Components of P Index Equations WI Total P Index compared to measured runoff losses for 86 site years using measured sediment and runoff volume in the equations P Index WI y = 0.81x R 2 = Measured Measured total P in lb runoff acre -1 lb/acre/yr -1

11 Year-to-year variability in precipitation means annual P Index values will not match measured loads P Index WI y = 0.28x r² = Measured total P in surface runoff lb/p/yr Measured total P in runoff lb/acre/yr

12 P Index Varies with Management: Driftless Area Example Soil test P = 70 ppm Fall chisel in 10,000 gal/acre dairy manure 5 T/a/yr erosion No till, fall apply 10,000 gal/acre dairy manure 2 T/a/yr erosion No till, winter apply 7,000 gal/acre dairy manure 2 T/a/yr erosion

13 P Index Varies with Management: Eastern Wisconsin Example Soil test P = 70 ppm Fall chisel in No till, fall apply No till, winter apply 10,000 gal/acre 10,000 gal/acre 7,000 gal/acre dairy dairy manure dairy manure manure 1.3 T/a/yr erosion 0.5 T/a/yr erosion 0.5 T/a/yr erosion

14 P Index over time with continuous corn silage Marathon County, Loyal silt loam, 4% slope. Initial soil test P is 100 ppm. Corn silage, 18 in rows. Fall chisel plowed or no till. With and without 12,000 gallons/acre liquid dairy manure in Fall.

15 County Soil Type Soil Test P and Organic Matter Field Slope PD Delivery Factor Field Slope Length Tillage Rotation crops and yields Manure Applications P Fertilizer Applications Downfield Slope to Surface Water Distance to Surface Water Stream Field

16 P Index: P Index: Estimate of annual storm flow delivery potential to nearest surface water

17 P Loss Potential Varies Across A Watershed Acres WI P Index

18 Similar watersheds have similar PI Index distribution Paired watersheds in Driftless Area cropland, intensive grazing Acr res % acres above 6 Average soil test P: ppm Average soil loss: ~ 2.5 T/acre/yr Average WI P Index: WI P Index 17% acres above 6 Acres WI P Index

19 Dane County N. Fork Pheasant Branch Cropland Average soil test P: 93 ppm Average soil loss: 2.5 T/acre/yr Average WI P Index: Acr res % of acres have PI greater than WI P Index Source: Corey Anderson

20 Lake Montello, Marquette County Cropland Average soil test P: 64 ppm Average erosion: 1.2 T/a/yr Avgerage WI P Index:1 Acres % of acres are over WI P Index

21 Acres 7000 Initial distribution WI P Index Acres 7000 All fields managed to PI of 6, Results in 26% load reduction WI P Index

22 Need to quantify other sources of P delivery to stream Storm loads: Dry lots, night pastures Barnyards Bank erosion Base loads: Groundwater Cattle in stream channels Phosphorus sorption and release from sediments Tile drains

23 Wisconsin P Index Basics for Watershed Planning Reasonable field rating tool Fields vary Watersheds vary