Phosphorus Site Index (PSI) and the Phosphorus Management Tool (PMT)

Transcription

1 Phosphorus Site Index (PSI) and the Phosphorus Management Tool (PMT) Patricia Steinhilber Department of Environmental Science & Technology Agricultural Nutrient Management Program University of Maryland

2 Understanding Phosphorus Issues Why are some soils high in phosphorus? Why is phosphorus a problem? When is P risk assessment required? What aids exist to assist calculation of the risk assessment tools?

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

4 Why Worry About Excess P? Eutrophication 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 and shellfish suffocate.

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

6 When are P Risk Assessments Required? If FIV-P is 150 or greater on any field and grower intends to apply any P-bearing material, it is required.

7 Soil Test P (FIV) EXCESSIVE OPTIMUM MEDIUM LOW OK Agronomic Environmental

8 Phosphorus Soil Test Correlation Potential Environmental Problems 0 LOW MED HIGH/OPTIMUM VERY HIGH/EXCESSIVE

9 The P Risk Tools Phosphorus Site Index (PSI) in use for a number of years gradually being phased out Phosphorus Management Tool (PMT) required on some farms in 2018 phase-in on all farms by 2022

10 Feature PSI PMT erosion x x runoff x x leaching potential subsurface drainage x x distance to surface water x x buffers x x priority of watershed soil test x x* P applications (fert & organic) x x timing and method of application x x x x

11 Information Tied to Soil Determine dominant map unit (or soil type) Web Soil Survey map of each field with map unit summary Essential properties soil erodibility drainage class permeability class hydrologic soil group (HSG)

12 Dominant Map Unit (or Soil Type) soil map unit (or soil type) with the greatest percentage area in a field multiple map units of the same type? combine areas of same types GgA 30%; GgB 30%, MaB 40% add same soil types together and use the map unit with higher slope as dominant map unit - GgB copy of map and map unit summary should be in client s file

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14 Information from Grower crop rotation type and timing of all tillage operations all nutrient sources with timing and method of application presence and width buffers presence of water features

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16 Estimating Erosion (average long-term soil loss) USLE Universal Soil Loss Equation RUSLE Revised Universal Soil Loss Equation RUSLE2 Revised Universal Soil Loss Equation v.2 currently the most accurate tool

17 Abbreviation RUSLE Factors R * K * LS ** C P rainfall quantity and intensity soil erodibility slope length and gradient crop and residue management conservation practices

18 Download at:

19 Phosphorus Site Index (PSI) Paradigm site features transport pathways management practices High Transport High Source (Part A) (Part B) source characteristics

20 PSI Interpretation P Loss Rating Interpretation 0 50 LOW potential for P movement from site. N-based recommendation is satisfactory MEDIUM potential for P movement from site. Limit P applications to amount expected to be removed from field by harvest or to soil test P recs. N-based recommendation 1 year of 3. P-based recommendation 2 years of HIGH potential for P movement from site. Use P-based recommendation. Limit P applications to expected removal or soil test P recs. > 100 VERY HIGH potential for P movement from site. No P should be applied to this site. Implement active remediation techniques to reduce P loss potential.

21 Phosphorus Management Tool (PMT) Paradigm Management Subsurface Drainage + + Management Management Transport Source Transport Source Transport Source Runoff Particulate (Erosion)

22 UM-PMT Interpretation Score low (0-50) medium (51-100) high (>100) Interpretation P applications shall not exceed P removal over the three-year period; can t exceed N rec of crop to which it is applied P removal the year of application No P can be applied

23 Stand-alone version Recommendations and PMT combined

24 Let s review June 2015 Reg Update no P application if field s FIV-P is 500 determine both PSI and PMT for other fields gradual phase-out of PSI replaced with PMT only

25 P Risk Assessment Tools If you do not need them now, keep it that way.