Annual P Loss Estimator (APLE) - University Of Maryland APLE...APLE Properties Excel spreadsheet...
Transcript of Annual P Loss Estimator (APLE) - University Of Maryland APLE...APLE Properties Excel spreadsheet...
Annual P Loss Estimator (APLE)
User-friendly Model for Annual,Field-Scale Phosphorus Loss
Peter VadasUSDA-ARS Dairy Forage Research Center
Madison, WI
Dairy Forage Research Center
Agriculture continues to be identified as important sourceof non-point phosphorus
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Phosphorus input to water bodiescontinues to be an issue
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What do we need to know about P loss from farms?
How much is lost?
How much is transferred?
What’s the impact?
How do we estimate how much P is lost?We measure.
Scenarios to monitor?Soil (clay, OM) 4Soil P status x 3Erosion rate (land use, tillage) x 4Runoff amounts x 3P application rate x 3P application type (fertilizer, animal species) x 3P application method (surface, injected) x 3Years of weather x 3
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We can’t possibly measure everything everywhere.How should we identify fields or practices that need attention?
Computer models are an important tool.
Models can be cost and time-effective
Runoff
Erosion
soil
landscapeweather
management
soil P
manure
fertilizerDrainage Soluble P
Sediment P
We know P loss is complex, but our decisions are limited by ability to process only a few interactions at a time. Models allow us to …
1. Map out all interactions to see how they influence P loss
2. Find practices with greatest impact, negative and positive
3. Identify the most important knowledge gaps (research)
4. Make decisions based on information beyond our own experiences
They are black boxes
Models make us nervous
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Models make us nervous, cont…
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When should we use a model?
We feel models improve our ability to make decisions because we …
Understand and agree with science and data behind them
Understand and agree with how they work and generate output (transparency)
Agree with how they are used given their structure and processes
Need monitoring and modeling – whole greater than sum of parts
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Current P loss model options
Complex, quantitative
Simple risk assessment
SWATAPEX
Bay Model
P Index
User friendly, quantitative
APLE
Farm to Watershed
Field Field
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APLE Properties
Excel spreadsheet model that estimates (lb/ac) annual, field-scale, dissolved and sediment P loss in surface runoff
Intended to function like a P Index
Estimate P loss for given set of management, soil P, erosion, runoff conditions
Be more process-based than most P Indexes, but much more user-friendly than APEX, SWAT type models
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APLE Inputs
APLE Inputs
Dissolved P Loss from Surface Manure, Fertilizer
All P not lost in runoff goes into soil
X
Available P on Surface
P on surface
P applied - P into soil from tillage, liquid manure infiltration
Availability factor
Precip.
Runoff Distribution FactorX X
Dissolved P in Runoff
Fertilizer: 100%Manure: % WEP
(Vadas, 2006)
(Vadas et al, 2009)
(Vadas et al., 2004, 2005, 2008)
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Dissolved and Sediment P Loss from Soil
Dissolved Soil Runoff P = (Soil Labile P) (0.005) (Annual Runoff)
Sediment P Loss = (Eroded Sediment)(Soil Total P)(P Enrichment Ratio)
Menzel et al. (1980) Sharpley (1980)
Vadas et al. (2005)
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Soil Total P
Organic P
+ LabileP
Active P
Stable P
++
From OMFrom
Mehlich-3 P
PSP
P Sorption Parameterfrom soil OM, clay, Labile P
(Vadas and White, 2010)
From Active P
Jones et al. (1984) Sharpley et al. (1984)
From Labile P and PSP
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P Leaching out of topsoil
P in Soil(mg/kg)
P concentration in leachate (mg/L)
Soil P = (a)(ln Leachate P) + b(Vadas, 2001)
MAX. (Nelson et al.,
2005)
P Leaching out of topsoil
% precip. leaching through topsoil
Layer depth (inches)Nelson et al. (2005)
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Soil P changes over time
Manure P
Organic P
5% 95%(100% fertilizer P)
Active P
Stable P
Labile P
Distribute P based on PSP
Two layers simulated within topsoil for P stratification
P mixed between layers based on degree of mixing
Crop P uptake from topsoil layers in proportion to relative soil P amounts
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APLE Output
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APLE P Loss and Soil P Evaluation
For P loss, used measured data from 24 studies from 13 different states, Australia, and Ireland
Used reported management data, measured soil P, runoff, erosion as inputs
For soil P, used measured data from 19 studies
Monitored changes in soil P from 1 to 25 years
Used reported management data as inputs
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APLE Soil P Validation
APLE P Loss Evaluation
y = 1.01x + 0.03r² = 0.78
0
5
10
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0 5 10 15 20 25 30
Est
imat
ed
P L
oss
(kg
/ha
)
Measured P loss (kg/ha)
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APLE
Measured P loss
correctlowhigh
050
100150200250300350400450
0 5 10 15 20 25 30P
Inde
x
Measured P lossr2 0.78 0.15
Correct 83% 53%
Low 10% 11%
High 7% 35%
High erosion, low P application
Low runoff, erosion high P application
APLE vs P Index
What is Proper Use for APLE?
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Best use of APLE
Appropriate
Education about factors of P loss, in format that makes sense and is conceptually correct
Directionally correct – If I do “X”, will P loss go up or down?
Quantitative uses
Designed to estimate actual P loss
Dynamic changes in P loss and soil P over time
Specific sources and pathways of P loss
Not Appropriate
Event-based, spatial, beyond edge-of-field evaluations
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2
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Case 1 Case 2 Case 3 Case 4 Case 5 Case 6
Run
off P
Los
s (lb
/ac)
Manure Soluble PSoil Soluble PSediment P
Case 1: 50 STP, 1 ton/ac erosion, 3 in runoff, 45 lb P/ac liquid on surfaceCase 2: 50 STP, 3 ton/ac erosion, 6 in runoff, 45 lb P/ac liquid tilledCase 3: 50 STP, 5 ton/ac erosion, 9 in runoff, 45 lb P/ac liquid tilledCase 4: 100 STP, 1 ton/ac erosion, 3 in runoff, 45 lb P/ac liquid on surfaceCase 5: 100 STP, 3 ton/ac erosion, 6 in runoff, 45 lb P/ac liquid tilledCase 6: 100 STP, 5 ton/ac erosion, 9 in runoff, 45 lb P/ac liquid tilled
Keeping P Loss Low
Feeding Less P0.5 % 0.3 %
3 ton/ac erosion
6 in runoff
45 lb P/ac liquid on surface
9% less P loss; 20% less soil P
Soil P Buildup and Decline1.5 ton/ac erosion5 in runoff45 lb P/ac
No-till
Manure applied (180 lbP/ac) and tilled once every 4 years
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0.50
1.00
1.50
2.00
2.50
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3.50
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Run
off P
loss
(lb/
ac)
Year
P Loss in RunoffSoluble P from ManureSoluble P from SoilSediment P
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Meh
lich
3 So
il P
(ppm
)
Year
Mehlich 3 Soil PTop LayerBottom LayerWhole Topsoil
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
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Run
off P
loss
(lb/
ac)
Year
P Loss in Runoff
0
50
100
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250
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29
Meh
lich
3 So
il P
(ppm
)
Year
Mehlich 3 Soil P
APLE Summary
Attributes
User-friendly, requires same inputs as P Index
Represents most recent research in soil P, P loss algorithms
Based entirely on research data, no professional judgment
Easily accessed output on forms, source, quantity of P loss
Rapid assessment of P loss for given management and transport scenarios
Challenges
Requires runoff and erosion as input
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Current APLE Applications
Since 2011, downloaded by >600 users in 48 states, 42 countries
Integrated into widely-used watershed models to evaluate impact of agriculture on water quality (SWAT, EPIC, IFSM, Agro-IBIS, Chesapeake Bay Model)
Incorporated into P-Indexes for WI, KY, OR, WA, MD, Canada
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http://www.ars.usda.gov/Services/docs.htm?docid=21763