Tools for Phosphorus Management
Andrew SharpleyWater to Worth: Spreading Science and
SolutionsDenver, CO; April 1 – 5, 2013
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
ARS Land Grant
National P locations
• 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
Learning from the past
..it was mobile
Arkansas
Illinois
Virginia
New York
Outreach
Soil P & runoff P
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
P loss affected by many factors177
14444
4620
1
<1
97
55
DP
8
DP78
92
0
Tony Buda, ARS, PA
Soil P – ppmP added – kg P/ha/yrRunoff – litersP loss – kg P/ha/yr
HighsourceHigh
source
Hightransport
Hightransport
Critical Source AreaCritical 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)
Factors in P Index
• Runoff potential
• Erosion potential
• Leaching potential
• Proximity to stream
TransportSource• Soil P content
• Added P• Rate, method,
timing of fertilizer & manure
• Manure P solubility
1
0
2
3
P index value for the site0 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 high
High
Med
Low
Testing the P Index
Soil P, mg/kg
P loss is controlled by many factors
• 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
Where was the breakdown
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 LowV.
HighHigh
4.0 Low High Med. Low LowV.
highHigh
5.8 LowV.
highV.
highLow Med.
V. high
High
10.9 LowV.
highV.
highLow Med.
V. high
High
23.7 LowV.
highV.
highLow High
V. high
High
Southern P Indices
Osmond et al., 2012
• 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
P Indices should …
• 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
Database development
• 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
Model use
Farm gateBMPsDietary P mgt. &
use of enzymes enhances nutrient
absorption & reduces excretionManure
additivescan reduce P
solubility & NH3 loss
Manure treatmentSolid-liquid separation,
struvite, zeolite
Struvite
Subsurface injectionreduces P runoff & N
volatilization
Soil & manure testing
to tailor rates of P to apply
Source BMPs4 R’sAppropriate rate, method timing, &
placementof P can increase crop
uptake & decrease runoff loss
Rotational grazingreduces P runoff & N
leached
Stream bank
fencingDecreases P deposition in
streams
Transport BMPs
Conservation tillage
reduces P runoff
Riparian buffers
trap particulate nutrients
Cover cropsreduces P runoff
BMP Credit
Diversion 5%
Terrace 10%
Pond 20%
Fenced Pond 30%
Filter Strip 20%
Fenced Filter Strip 30%
Grassed waterway 10%
BMP effectiveness
BMPCredi
t
Fencing 30%
Riparian Forest Buffer 20%
Fenced Riparian Forest Buffer 35%
Riparian Herbaceous Cover 20%
Fenced Riparian Herbaceous Cover
30%
Field Borders 10%
BMP effectiveness
-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
BMP effectiveness
-40%
-15%
Farm pond (12)
-50%
-28%
-65%
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
River P @ HWY 59
Maumee River watershed
Sandusky River
watershed
MICHIGAN
Lake ErieLake Erie
OHIO
Lessons from Lake Erie Basin
Trends in P – Maumee River
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
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
Trends in P – Maumee River
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
Trends in P – Maumee River
• 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 …….
• Researchers need to step back and look at the big picture
The bottom line
Thank you
Questions ??
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