70th SWCS International Annual Conference July 26-29, 2015 Greensboro, NC

1. PRZM to Predict Hydrology, Atrazine
Concentrations, & BMP Effectiveness
Lula Ghebremichael, Clint Truman, Sunmao Chen, Mark White
Syngenta Crop Protection, LLC
SWCS 2015 Conference July 26- 29, 2015, Greensboro, NC

2. 2
Outline
● Goal
● Model description
● MO-07 watershed
● Model performance
● BMP effectiveness
Classification: Public

3. 3
Goal
Evaluate BMPs using a modeling approach to select effective BMPs
and enhance stewardship programs
Classification: Public

4. 4
Model Description
● PRZM (Pesticide Root Zone Model)
● Developed by U.S.EPA (Carsel et. al.1985)
● Official core model for pesticide registration at U.S. EPA
Classification: Public
Hydrological & Erosion Processes
Surface runoff SCS curve number
Water balance (Inflow = Outflow + ΔStorage)
Erosion MUSLE
Pesticide Processes
Application method Various methods
Partitioning (Sorption/desorption) Equilibrium; Linear
Degradation First-order
Plant Uptake, Runoff, Erosion, Volatilization, Foliar Wash-off
ModelFeatures

5. 5
PRZM Application for Regulatory Environmental Exposure
Assessment
● Runoff Events and Pesticide loading  Pesticide Concentration in
Standard pond
● Pesticide mass predicted for Runoff Events only
Classification: Public
PRZM EXAMS
1 hectare
(2 m pond)
10 hectare
field area

6. 6
PRZM Application On MO-07 Watershed
Classification: Public
PRZM Model
Atrazine mass from
runoff events (multiple
fields in a watershed)
Stream flow “measured”
Atrazine Concentration

7. 7
PRZM Model Inputs
Classification: Public
Land use
Soil Inputs
Precipitation (cm/day)
Pan evaporation data (cm/day)
Temperature (Celsius)
Wind speed (cm/sec)
Solar radiation (Langley)
Weather
Chemical
Legend
OM_MO07N_proj
SdvOutpu_1
1.25 - 1.5
1.50 - 2.0
2.00 - 2.4
2.4 - 2.6
2.60 - 3.0
Legend
BD_MO07N_proj
SdvOutpu_1
1.29-1.31
1.31-1.4
1.4-1.480
Legend
ST_MO07N_proj
(Surface Layer), {DCD, <}
Clay loam
Fine sandy loam
Loam
Loamy sand
Sandy loam
Silt loam
Silty clay loam
Not rated or not available
BDOM Texture

8. 8
Model Evaluations
Classification: Public
Hydrology Atrazine concentrations
Lack of field-level data for model evaluation
Runoff events aggregated from watershed
compared to “measured runoff” (baseflow
separation)

9. 9
Predicted Atrazine Concentration: 2010-2014
Limitations
● Incomplete to reflect stream
flow concentrations
● Used single atrazine
application date for all fields
in the watersheds
● Need to use crop planting
progress data to schedule
application dates across corn
fields
● Runoff timing and travel time
Classification: Public

10. 10
Best Management Practices Modeled
● Soil Incorporation (e.g. Phillips Harrow  spray followed by
incorporation in one pass, ~ 5 cm incorporation depth and complete
mixing)
● Split application (pre-, post-emergence)
Classification: Public

11. 11
Model Predicted BMPs Effectiveness
Classification: Public
Concentration vs. Mass
2010
2011
2012
2013
2014
Concentration vs. Mass

12. 12
Summary
● PRZM performances in predicting hydrology and atrazine concentration
- incomplete picture of flow and atrazine conc. in streams
- may be beneficial to add baseflow, runoff timing & travel time
components
- need refinement to model inputs (e.g. application date; rainfall)
● PRZM application for assessing BMPs effectiveness
- relative BMPs effectiveness at field-level in surface runoff
- limited number of BMP can be assessed
● BMP effectiveness
- incorporation (~43%); split application (~ variable)
- concentration vs. mass
Classification: Public