Annual P Loss Estimator (APLE) - University Of Maryland APLE...APLE Properties Excel spreadsheet model that estimates (lb/ac) annual, field-scale, dissolved and sediment P loss in

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


Phosphorus input to water bodiescontinues to be an issue


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

11,664

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


Models make us nervous, cont…


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


Current P loss model options

Complex, quantitative

Simple risk assessment

SWATAPEX

Bay Model

P Index

User friendly, quantitative

APLE

Farm to Watershed

Field Field


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


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)


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)


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


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)


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


APLE Output


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


APLE Soil P Validation

APLE P Loss Evaluation

y = 1.01x + 0.03r² = 0.78

0

5

10

15

20

25

30

0 5 10 15 20 25 30

Est

imat

ed

P L

oss

(kg

/ha

)

Measured P loss (kg/ha)

0

5

10

15

20

25

30

0 5 10 15 20 25 30

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?


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


0

2

4

6

8

10

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

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29

Run

off P

loss

(lb/

ac)

Year

P Loss in RunoffSoluble P from ManureSoluble P from SoilSediment P

0

50

100

150

200

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 PTop LayerBottom LayerWhole Topsoil

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29

Run

off P

loss

(lb/

ac)

Year

P Loss in Runoff

0

50

100

150

200

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


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


http://www.ars.usda.gov/Services/docs.htm?docid=21763

Documents

Annual P Loss Estimator (APLE) - University Of Maryland APLE...APLE Properties Excel spreadsheet model that estimates (lb/ac) annual, field-scale, dissolved and sediment P loss in