This document summarizes a presentation about tools for phosphorus management. It discusses the history of phosphorus risk assessment and revisions to nutrient management standards. It also outlines outcomes from national phosphorus research projects, including standardized rainfall runoff study methods. Additionally, it provides an overview of phosphorus indices used for risk assessment and nutrient planning, and discusses best management practices to reduce phosphorus loss from agricultural lands.

1. Tools for Phosphorus
Management
Andrew Sharpley
Water to Worth: Spreading Science and Solutions
Denver, CO; April 1 – 5, 2013

2. History risk assessment
Revision of the NRCS 590 Nutrient
Management Standard & P Indices
Its use & misuse for P management
BMPs and their assessment
The way forward
Today’s presentation

3. ARS
Land Grant

4. • National P Research Project outcomes
 Standardized methods for rainfall – runoff studies
 Established relationships between STP and runoff
 Integrated into P Indices
 Incorporated into NMP process
• Success partly due to
 Group effort – Land Grant & ARS
 Flexibility to adapt to State needs

6. ..it was mobile

7. Arkansas

8. Illinois

9. Virginia

10. New York

11. Outreach

13. Dissolved P
mg L-1
Mehlich-3 P, mg kg-1
FD-36 watershed - PA
1
0
2
3
0 200 400 600 800
R2 = 0.86
Crop response
200 mg L-1
Change point

14. P loss affected by
many factors177
144
44
4620
1
<1
97
55
DP
8
DP78
92
0
Tony Buda, ARS, PA
Soil P – ppm
P added – kg P/ha/yr
Runoff – liters
P loss – kg P/ha/yr

15. High
source
High
transport
Critical Source Area
Led to the 80/20 rule:
80% of P comes from
20% of land area
Risk assessment used by most states for
nutrient management planning (CPS 590)

16. • Runoff potential
• Erosion potential
• Leaching potential
• Proximity to stream
TransportSource
• Soil P content
• Added P
• Rate, method, timing
of fertilizer & manure
• Manure P solubility

17. 1
0
2
3
P index value for the site
0 50 100 150 200
R2=0.80
75 kg P/ha TSP
112 kg P/ha
poultry litter
150 kg P/ha
poultry manure
Runoff P,
g/ha
Very highHighMedLow
Soil P, mg/kg

18. 

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P loss is controlled by many factors

19. • Disparity among Indices across the country
 Varied with soils, topography, & state priorities
• Often, not leading to a decline in STP nor
improvement in water quality
 Legacy effects
• Perceived as farmer friendly
• The P Index was never meant to be the
solution to P management issues

20. P loss
kg ha-1
AL AR GA MS NC TN TX
0.5 Low Low Low Low Low High Med.
2.7 Med. High High Low Low V. High High
4.0 Low High Med. Low Low V. high High
5.8 Low V. high V. high Low Med. V. high High
10.9 Low V. high V. high Low Med. V. high High
23.7 Low V. high V. high Low High V. high High
Osmond et al., 2012

21. • Appropriately account for major sources
& processes determining P loss & rank risk
of loss for any given site
• Directionally and magnitudinally correct
• Interpretations based on assigned risk are
equivalent across state borders, given
similar site & water resource conditions
• Where inadequacies exist, the causes can
be identified & addressed

22. •At a minimum this should include
 Site runoff, management, climate,
water quality
 Event, planning / rotation period &
annual loss
 Natural rainfall
• Network of sites and data exchange
being developed – Kleinman et al.
• MANAGE – Daren Harmel

23. •Select appropriate model
 APEX, APLE, DrainMod
 Locally calibrated (within state)
 Event, planning / rotation period &
annual loss
• Model & Index must estimate P loss &
simulate P mobilization & transport
over same time scales

24. Dietary P mgt. & use
of enzymes enhances
nutrient absorption &
reduces excretion
Manure additives
can reduce P
solubility & NH3 loss
Manure treatment
Solid-liquid
separation, struvite,
zeolite
Struvite

25. Subsurface injection
reduces P runoff & N
volatilization
Soil & manure
testing
to tailor rates
of P to apply
4 R’s
Appropriate rate, method
timing, & placement
of P can increase crop
uptake & decrease runoff
loss

26. Rotational grazing
reduces P runoff & N
leached
Stream bank
fencing
Decreases P
deposition in
streams
Conservation
tillage
reduces P runoff
Riparian buffers
trap particulate
nutrients
Cover crops
reduces P runoff

27. BMP Credit
Diversion 5%
Terrace 10%
Pond 20%
Fenced Pond 30%
Filter Strip 20%
Fenced Filter Strip 30%
Grassed waterway 10%

28. BMP Credit
Fencing 30%
Riparian Forest Buffer 20%
Fenced Riparian Forest Buffer 35%
Riparian Herbaceous Cover 20%
Fenced Riparian Herbaceous Cover 30%
Field Borders 10%

29. -100 1000
Effect on total P loss, %
Decreased loss Increased loss
Manure mgt. system (14)
Nutrient mgt. plan (14)
Stream fencing (3)
Vegetated buffers (34)
Dinnes et al., 2004 & Gitau, 2005
-40%
-15%
Farm pond (12)
-50%
-28%
-65%

30. AR Water Resources Center, 2012
Dissolved P Total P
2000 0.224 0.377
2003 0.148 0.244
2011 0.070 0.130
Mean annual concentration, ppm

31. Maumee River
watershed
Sandusky River
watershed
MICHIGAN
Lake Erie
OHIO
Lessons from Lake Erie Basin

32. Annual flow-weighted total P, ppm
1975 1985 1995 2005
0.8
0.6
0.4
0
0.2
50% decrease
Dave Baker & Peter Richards, OH

33. Adoption of mulch and no-till soybeans, %
1975 1985 1995 2005
0.12
0.09
0.06
0
0.03
Annual flow-weighted dissolved P, ppm
75% decrease
80
60
40
20

34. 1975 1985 1995 2005
0.12
0.09
0.06
0
0.03
Adaptive management may
have reduced nutrient loss
 Incorporation of fertilizer and
manure
 Winter cover crops
 Spring fertilization

35. • Spring workload is huge with more
time-sensitive tasks
• Fertilizer usually costs more in spring
• Less soil compaction on frozen ground
But the reality is …….

36. • Researchers need to
step back and look
at the big picture