The Phosphorus Management Tool

Transcription

1 The Phosphorus Management Tool Heather Hutchinson Nutrient Management Specialist June 18, 2013

2 Understanding Phosphorus Why are soils high in phosphorus? Why is phosphorus a problem? How is phosphorus loss potential measured? How can phosphorus loss potential be reduced? In-depth training opportunities

3 Why are some Soil P Levels Excessive? over application of commercial fertilizer P recs for some crops continue into the excessive range (vegetables, tobacco) using organic nutrient sources at N-based rates

4 The imbalance between required and actual application rates for phosphate when dairy manure is applied to supply the N recommendation. Total N = 366 lbs/a P Excess Required P = 38 lbs/a Excess P = 57 lbs/a lbs of nutrient applied per acre Based on corn yielding 150 bu/a, grown on soil with medium phosphorus soil test.

5 Excessive Optimum Medium Low OK

6 UM Soil Testing Lab 2003 Ag Samples All Regions % of soils with FIV-P > 150

7 Why Worry About Excess P? Phosphorus is an essential nutrient root development and plant growth grain and fruit development better resistance to stress disease pest moisture However too much phosphorus can lead to environmental problems (e.g., eutrophication)

8 Why Worry About Excess P? Eutrophication P is the limiting nutrient in fresh water systems Excess P that enters surface waters feeds algal blooms The blooms shade out underwater grasses Dying grasses (and algae) utilize oxygen in the decay process Fish suffocate Etc.

9 Sources P Sources & Transport Transport N-P-K Leaching Tile flow Subsurface flow Modified from Sharpley & Gburek, USDA-ARS

10 P Transport to Surface Waters Primarily via surface flow Dissolved P 100% biologically available Particulate P carried on eroded particles, not immediately bio-available Leaching and lateral subsurface flow in limited situations If the soil becomes saturated with P the potential for P loss increases significantly

11 How Much P is Lost? Usually less than 5% of applied P is lost but this amount often exceeds the critical values for accelerated eutrophication.

12 When do we need to worry about P? Soil test FIV-P 150

13 How do you address P? Phosphorus Management Tool (PMT) Second Generation Tool for evaluating the relative risk of P transport from agricultural fields which result from: Site characteristics Climate P sources (organic and inorganic sources) Soil test P Encourages management practices to protect water quality

14 PMT vs. PSI Phosphorus Site Index Current tool focuses on source and transport Phosphorus Management Tool Coming very soon! Focuses on source, transport and management

15 How does the PMT work?

16 Management: Critical Source Area Management Critical Source Area Transport Source

17 Determining Transport Potential Field evaluation % slope Length of slope Distance to surface water Type and width of buffer Farmer interview Tillage operations Crop rotation Planned nutrient applications (rate/type/method) Soil Tests (including P saturation ratio OR Melich-3 Al and Fe) RUSLE

18 Revised Universal Soil Loss Equation (RUSLE) RUSLE estimates average long-term soil loss caused by rainfall and runoff.

19 RUSLE Erosion slide A (soil loss) = R x K x LS x C x P

20 R = Rainfall Factor accounts for amount, timing, and intensity of rainfall differs from county to county

21 K = Erodibility Factor accounts for susceptibility of soil particles to detach and move with water differs across soil types

22 LS = Slope Length & Steepness Factor accounts for slope length and slope steepness must be measured on site

23 C = Cover & Management Factor accounts for crop rotation, tillage, and residue

24 P = Support Practices Factor Includes: contour farming strip cropping terraces

25 RUSLE Erosion slide A (soil loss) = R x K x LS x C x P

26 PMT Calculation Management Runoff + + Management Management Transport Source Transport Source Transport Source Particulate Subsurface Additive pathway factors Appropriate in areas where one pathway dominates

27 Calculation UM-PMT = Particulate + Runoff + Subsurface Drainage Each pathway has 3 components High P-source and high transport potential are necessary for a high score Management can significantly improve the phosphorus loss score

28 Particulate P Source = Soil test P Transport = RUSLE Management: Covered by RUSLE and combined distance buffer factor

29 Distance-Buffer Factor Table 1. Distance from edge of field to surface water and resulting distance factor. Distance from Surface Water Distance Factor >500 feet to 500 feet to 349 feet to 199 feet 0.8 <100 feet 1.0 Surface water includes any permanent, continuous, physical conduit for transporting surface water, including permanent streams and ditches even if they only flow intermittently during the course of the year. Table 2. Types of buffers and resulting buffer factors that will modify the Distance Risk Factor to yield the combined Distance Buffer Factor. Type of Buffer Buffer Factor >50 feet Riparian Zone 0.7 >50 feet Permanent Vegetated Buffer Meeting USDA-NRCS Standards 0.8 >35 feet Permanent Vegetated Buffer 0.9 <35 feet Vegetated Buffer or No Buffer 1.0 Permanent vegetated buffers do not receive any phosphorus applications.

30 Phosphorus Saturation Ration (PSR) 80 (more informative than Soil Test P) Dissolved Reactive P (mg/kg) High P soil Keyport sandy loam Donlonton sandy loam Matapeake silt loam Mattapex silt loam P Degree of P Saturation (%) ox / 0.5 (Fe ox + Al ox ) Butler & Coale, 2003

31 Runoff: Surface Dissolved P Source = Soil s PSR + Available P in nutrient source Assumes equal contribution from nutrient source and soil Penn State and A&L, VA will provide Al and Fe from archived Melich-3 analyses for a fee Waters uses Melich-1 Transport = Factor of soil permeability class and slope Management = Application method & timing and combined distance-buffer factor

32 Surface Application Methods & Timing Table 4. Phosphorus application method factor for surface transport component (AM r ). Application Method Value None Applied 0 Subsurface placement or immediate full incorporation (>90% residue) 0.2 Incorporated within 5 days of application ( 50% residue) 0.4 Surface applied March - Nov. OR incorporated after 5 days OR <50% residue 0.6 Surface applied or incorporated after 5 days Dec. - Feb. 0.8

33 Subsurface Drainage: Subsurface Dissolved P Source = Soil s PSR + Available P in nutrient source Assumes equal contribution from nutrient source and soil Transport = Soil drainage class x Hydrologic soil group Management = Application method & timing Only necessary when artificial drainage is used

34 Subsurface Application Methods & Timing Table 3. Phosphorus application method factor for subsurface transport component (AM sub ). Application Method Value None Applied 0 Incorporated within 5 days with soil mixing (precludes straight aerator) March - Nov. Incorporated within 5 days with soil mixing (precludes straight aerator) Dec. - Feb Surface applied and subsurface placement without soil mixing (includes banded fertilizer and injection without soil mixing) March - Nov. Surface applied and subsurface placement without soil mixing (includes banded fertilizer) Dec. - Feb

35 Score > 100 Interpretative categories in the revised PSI Generalized Interpretation of P Loss Rating LOW potential for P movement from this site given current management practices and site characteristics. Soil P levels and P loss potential may increase in the future due to continued nitrogen-based nutrient management. Total phosphorus applications should be limited to no more than a three-year crop removal rate applied over a three year period. MEDIUM potential for P movement from this site given current management practices and site characteristics. Practices should be implemented to reduce P losses by surface runoff, subsurface flow, and erosion. Phosphorus-based nutrient management planning should be used for this site. Phosphorus applications should be limited to the amount expected to be removed from the field by crop harvest or soil-test based P application recommendations. HIGH potential for P movement from this site given current management practices and site characteristics. No phosphorus should be applied to this site. Active remediation techniques should be implemented in an effort to reduce the P loss potential from this site.

36 Example Recommendation PMT Score Low Crop and Yield Goal Corn Grain 150 bu/ac Medium Corn Grain 150 bu/ac High Corn Grain 150 bu/ac Allowed P2O5 Application per Year 180 lbs/ac (60 lbs x 3 yrs) Tons Litter/yr (avg analysis) 3.3 Ton 129 lbs/n 177 lbs/p2o5 Gals liquid dairy/yr (avg analysis) 10,822 gal 150 lbs/n 108 lbs/p2o5 60 lbs/ac 1.1 Ton 5,988 gal None 0 0

37 Summary P is vital to crop productivity Repeated over-application presents environmental hazard Most P export comes from a small portion of the watershed as a result of relatively few storms if water or soil do not move from a field or below the root zone, then P will not move Management plays a significant role in reducing P losses and must be addressed

38 PMT Field Training Practical Experiences in Nutrient Management September 12, 2013 at Western Maryland Research and Education Center in Keedysville Explanation of the PMT Field Measurements for the PMT Other educational sessions including manure spreader calibrations, yield checks, PSNT/FSNT, etc.

39 Questions?