Phosphorus Site Index

Transcription

1 Phosphorus Site Index An Introduction Fundamentals of Nutrient Management June 2, 2010 Heather Hutchinson Nutrient Management Specialist University of Maryland

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? When/where to attend in-depth training

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 disposal rates or 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 UM Soil Testing Lab Optimum plus Excessive Percent of all ag field samples

6 Soil Test P (FIV) EXCESSIVE 50 0 Agronomic OPTIMUM MEDIUM LOW OK Environmental

7 UM Soil Testing Lab 2003 Ag Samples All Regions % of soils with FIV-P > 150 % of ag field samples Allegany Anne Arundel Baltimore Calvert Caroline Carroll Cecil Charles Dorchester Frederick Garrett Harford Howard Kent Montgomery Prince George's Queen Anne's St. Mary's Somerset Talbot Washington Wicomico Worcester

8 A Misconception About Phosphorus Erosion control will eliminate P losses from a field.

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

10 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 suffocate Etc.

11 How Do We Prevent P from Entering Surface Waters? Optimize P fertilizer application rates Minimize potential for loss by adjusting management strategies

12 Field Factors Affecting P Loss in Runoff soil test P nutrient applications -rate - method - timing (relative to first few intense rainfalls)

13 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.

14 PSI: A Risk Assessment Tool Allows us to estimate potential for phosphorus losses to surface waters from specific sites.

15 Integrating Source and Transport Factors The critical source area concept: critical areas result from a high source of P and high transport High Source High Transport

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17 High

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20 High Source High Transport

21 PSI If FIV-P is 150 or greater on any field and you intend to apply any P-bearing material, it is required.

22 PSI Considers phosphorus losses due to: (A) Site and Transport Characteristics AND (B) Management Practice and Source Characteristics

23 Part A of the PSI Evaluates site and transport conditions 6 factors are evaluated

24 Maryland Phosphorus Site Index, Part A: P loss potential due to site and transport characteristics Characteristics Soil Erosion (tons/a) Phosphorus Loss Rating 2 X (tons soil loss/a/year) Value Soil Runoff Class Subsurface Drainage Leaching Potential Distance From Edge of Field to Surface Water (feet) Priority of Receiving Water September 2000 Negligible/ Very Low 0 Very Low 0 Low 0 >100 ft. 0 Category 2 0 Low 2 Low 2 <100 ft & >50 ft veg. buffer OR <100 ft & >25 ft veg. buffer & >25 ft additional no P application zone 2 Category 3 1 Medium 4 Medium 4 Medium 2 <100 ft & >25 ft veg. buffer & <25 ft additional no P application zone 4 Category 3, Selected 2 High Sum of Site and Transport Characteristics: 6 High 6 <100 ft & <25 ft veg. buffer & >25 ft additional no P application zone 6 Category 1 3 High 4 Very High Scaling Factor: X 0.02 Total Site and Transport Value: 8 Very High 8 <100 ft & <25 ft veg. buffer & <25 ft additional no P application zone 8 Category 1, Priority 4

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

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

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

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

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

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

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

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

33 PART A Soil Runoff Class Subsurface Drainage Leaching Potential

34 PART A Distance From Edge of Field to Surface Water Priority of Receiving Water

35 Maryland Phosphorus Site Index, Part A: P loss potential due to site and transport characteristics Characteristics Soil Erosion (tons/a) Phosphorus Loss Rating 2 X (tons soil loss/a/year) Value Soil Runoff Class Subsurface Drainage Leaching Potential Distance From Edge of Field to Surface Water (feet) Priority of Receiving Water September 2000 Negligible/ Very Low 0 Very Low 0 Low 0 >100 ft. 0 Category 2 0 Low 2 Low 2 <100 ft & >50 ft veg. buffer OR <100 ft & >25 ft veg. buffer & >25 ft additional no P application zone 2 Category 3 1 Medium 4 Medium 4 Medium 2 <100 ft & >25 ft veg. buffer & <25 ft additional no P application zone 4 Category 3, Selected 2 High Sum of Site and Transport Characteristics: 6 High 6 <100 ft & <25 ft veg. buffer & >25 ft additional no P application zone 6 Category 1 3 High 4 Very High Scaling Factor: X 0.02 Total Site and Transport Value: 8 Very High 8 <100 ft & <25 ft veg. buffer & <25 ft additional no P application zone 8 Category 1, Priority 4

36 Part B of the PSI Evaluates source and management practices 5 factors included

37 Part B: P loss potential due to management practice and source characteristics Characteristics Soil Test P Fertility Index Value P Fertilizer Application Rate (lbsp 2 O 5 ) Phosphorus Loss Rating 0.2 X FIV 0.6 X (lbs P 2 O 5 /A) Value P Fertilizer Application Method Organic P Application Rate (lbsp 2 O 5 ) None applied 0 Injected/ banded below surface, at least 2 15 Incorporated within 5 days of application 30 Surface applied Mar-Nov OR incorporated >5 days after application 45 PSC X (lbs. P 2 O 5 /acre) Surface applied Dec-Feb 60 Organic P Application Method None applied 0 Injected/ banded below surface, at least 2 15 Incorporated within 5 days of application 30 Surface applied Mar-Nov OR incorporated >5 days after application 45 Surface applied Dec-Feb 60 September 2000 Total Management and Source Value:

38 PART B University of Maryland Extension Fertility Index Value

39 Equivalent Phosphorus Index Threshold Levels A & L Labs (Richmond), Bray P1, P1 (ppm) Mehlich-3, P (ppm) Agri Analysis, Mehlich-3, P 2 O 5 (lb/a) 640 Brookside, Mehlich-3 (easily extractable), P (ppm) 123 Mehlich-3 (easily extractable), P 2 O 5 (lb/a) 565 Penn State, Mehlich-3, P (ppm) 129 Mehlich-3, P (lbs/a) 591 Spectrum Analytic, Mehlich-3 expressed as Bray, P (lb/a) 187 Mehlich-3, P (ppm) 134 U. of DE, Mehlich-1, P (index) 142 Waters, Mehlich-1, P (lb/a) 124

40 PART B P Fertilizer Application Rate (lbs P 2 O 5 /acre)

41 PART B P Fertilizer Application Method

42 PART B Organic P Application Rate (lbs P 2 O 5 /acre x PSC)

43 PSCs for Various Organic Sources P Source PSC swine manure 0.6 other manures, including 0.5 composted manures biosolids (BPR and BNR) 0.5 alum-treated manures 0.3 biosolids (other) 0.2

44 PART B Organic P Application Method

45 Part B: P loss potential due to management practice and source characteristics Characteristics Soil Test P Fertility Index Value P Fertilizer Application Rate (lbsp 2 O 5 ) Phosphorus Loss Rating 0.2 X FIV 0.6 X (lbs P 2 O 5 /A) Value P Fertilizer Application Method Organic P Application Rate (lbsp 2 O 5 ) None applied 0 Injected/ banded below surface, at least 2 15 Incorporated within 5 days of application 30 Surface applied Mar-Nov OR incorporated >5 days after application 45 PSC X (lbs. P 2 O 5 /acre) Surface applied Dec-Feb 60 Organic P Application Method None applied 0 Injected/ banded below surface, at least 2 15 Incorporated within 5 days of application 30 Surface applied Mar-Nov OR incorporated >5 days after application 45 Surface applied Dec-Feb 60 September 2000 Total Management and Source Value:

46 P Loss Rating Part A x Part B = P Loss Rating

47 Interpretation of P Loss Rating P Loss Rating Interpretation 0 50 LOW potential for P movement from site. N-based nutrient management planning 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 planning 1 year of 3. P-based planning 2 years of HIGH potential for P movement from site. Use P- based nutrient management planning. 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.

48 Practices That Reduce P Loss Risk Vegetated buffer size No-P application zones Application rates & methods Manure application at crop P-removal rates Crop rotations, cover crops Contour farming, strip cropping

49 PSI Classroom Session October 21, 2010 Maryland 4-H Center, College Park 9:30am 3:30pm

50 Any Questions?