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Managing
Atrazine Application |
| Introduction |
IntroductionAtrazine,
as one of major agricultural herbicides, has been used for weed control
in corn production for more than three decades. Atrazine is a valuable
herbicide for corn growers because it can effectively control weeds and
its cost is relatively low. However, atrazine is also susceptible to
leaching and runoff which may cause water pollutions. Frequent detection
of atrazine in water supplies has led the U.S. Environmental Protection
Agency (USEPA) to implement more restrictive guidelines for atrazine
use. Atrazine has frequently been found in Michigan waters with some
samples exceeding the drinking water standard. The St. Joseph River
watershed was labeled by USEPA as the largest contributor of atrazine to
Lake Michigan. Technical assistance and information about atrazine use
risks are needed for corn growers to archive high corn productivity
while keeping their drinking water safe. This
project uses the models developed by the U.S. Department of Agriculture
(USDA) and Geographic Information System (GIS) technology to produce
user-friendly risk assessment maps. St. Joseph County was selected as
the study area in this risk mapping project. Factors associated with
atrazine leaching and runoff are considered in risk assessment. By
having risk maps readily available for coops, consultants, applicators,
corn growers, the high potential risk areas can be identified when a
decision is being made about herbicide application. Risk maps can also
help farmers for record keeping on high risk areas where best management
is in place in compliance with environmental regulations. Methodology
Risk
Assessment Models: Two
models developed by the U.S. Department of Agriculture were used to
assess the risk of atrazine movement to water bodies (lakes, streams,
and groundwater): the Windows Pesticide Screening Tool (Win-PST) and the
Revised Universal Soil Loss Equation (RUSLE). Win-PST
uses qualitative ratings to classify the relative likelihood of
pesticide loss from field boundaries via runoff and from root zone via
percolation. The algorithm used for the screening procedure was
developed by Goss and Wauchope (1990) in the USDA. The procedure uses
the soil database provided by the USDA and pesticide database provided
by the US Environmental Protection Agency. The overall risk ratings are
based on the interactions of ratings for pesticides and soils using a
rule-based algorithm. These basic ratings are then adjusted by
site-specific conditions such as the method and rate of pesticide
application, field slope, soil macropores, water table, and probability
of rainfall. The risk ratings are classified as “high”,
“intermediate”, “low”, and for leaching, “very low”. The
results from Win-PST were used to generate the risk maps for atrazine
leaching potential to groundwater. The risk maps are color coded to
represent the different levels of risks. The
Institute of Water Research has worked with Win-PST approach in the past
three years. We have evaluated Win-PST with another USDA pesticide risk
assessment model National Agricultural Pesticide Risk Analysis (NAPRA).
We found that Win-PST can provide consistent and comparable assessment
with other risk assessment model. Our previous studies have also shown
that Win-PST is conservative regarding the risk of pesticide losses for
pesticides with high toxicity and low application rates (Da Ouyang,
1999). In
addition to assess the risk of atrazine loss to groundwater which is the
primary concern in St. Joseph county, we have provided the risk
assessment for surface water using RUSLE. RUSLE is a widely used soil
erosion model developed by the USDA. We used RUSLE to estimate the
potential risk of atrazine loss to the surface water from runoff and
sediment. RUSLE takes into account the following factors: A
= R * K * LS * C * P Where A
= estimated average soil loss in tons per acre per year The
risk maps for potential atrazine loss to surface water from runoff and
sediment-bound compound was generated based on soil loss in tons per
acre per year. Data
Source:
Soil
properties database and digital soil data were provided by the Natural
Resource Conservation Service, U.S. Department of Agriculture. Pesticide
properties database were from the U.S. Environmental Protection Agency (USEPA).
Soil and pesticide properties databases were included in Win-PST
program. Atrazine application and tillage management data were obtained
from Michigan State University Extension office and NRCS County Office
in St. Joseph, Michigan. GIS Technology: Maps were generated by using ArcView and
ArcExplorer GIS (Geographic Information System). This technology allows
us to generate geo-referenced maps, overlay different layers such as
soils, roads and county boundaries, and color code the risk areas.
Digital images with 4-meter resolution from the U.S. Geological Survey (USGS)
were used as the backdrop. Results and Products
The
main result for this project is to produce risk assessment maps for
atrazine application in the study area St. Joseph County. Map
products: Risk
maps are produced in both printed and digital format. Various scales of
maps (county, township, field-size level) are available based on the
user’s need. Map layers include soils, roads, streets with street
names, water systems (lakes, rivers, streams), digital photographs, and
risk ratings. By using a GIS software (ArcView or Arc Explorer), users
can easily zoom in/out the area of their interest and
select/deselect/overlay different data layers. Sample maps are attached
as appendix. Evaluation: Initial
map products in a selected township in Phase I have been presented to
the advisory team. Map products in Phase II have been completed in Fall
of 2000 with feedbacks from advisory team from Phase I, and more digital
soil data provided by NRCS. Phase II maps cover the entire St. Joseph
County and have again been evaluated by the advisory team in December
2000. Advisory team members include Rich Hodupp, Agricultural Agent in
St. Joseph County (now in Kalamazoo County), Jon Silsby, a certified
crop advisor in Michigan Wilbur-Ellis Company, Bill Foster, United Agri
Products (UAP), a ConAgra Company, Marcy Strefling, St. Joseph County
Agricultural Agent, and Bruce MacKellar, Van Buren County Agricultural
Agent. Map
Applications: With overlaying risk ratings and digital images
and other data layers, the risk map can help identify the important
information such as whether or not a field/residential area is in a high
risk area, and how far it is to the water body, etc. The information can
then be used to aid decision makers (e.g. corn growers and applicators)
in herbicide application if additional precautions need to be taken.
Corn growers can also use the risk maps to help record keeping for
atrazine use in their corn fields, especially when the field is labeled
high risk area. The risk assessment mapping system may help crop
consultants provide science-based recommendations in herbicide selection
and application methods to minimize the environmental risks. Combined
with GIS/GPS technology, the digital risk mapping program can be used as
a guiding system for herbicide application in corn production. Distribution: Color
coded risk maps are available in 8.5” x 11” paper hardcopy and in
CD-ROM. A free commercial GIS software ArcExplorer is distributed on the
CD with the risk map data to display the maps. Technical assistance will
be provided to users who want to use the risk maps in digital format on
our distributed CDs. Future Study:
This
project has demonstrated corn industry’s proactive and environmentally
conscientious herbicide use philosophy. As the risk assessment /mapping
technology is deployed for atrazine, it will provide a proof of how the
technology can help corn growers to achieve profitability and maintain
safe drinking water. With additional funding made available, the risk
mapping system can be applied to other compounds and other counties.
Using this technology in corn production will assist in assuring
continued availability of cost effective herbicide products to corn
growers, and therefore benefits the corn industry in Michigan. ReferencesBagdon,
J., E. S. Hesketh, S. Plotkin, and M. S. Hugo (1994). NAPRA Technology
Transfer Overview: An Introduction. NAPRA Technical Notes. Goss,
D., and R. D. Wauchope (1990). The SCS/ARS/CES Pesticide Properties
Database: II Using it with soils data in a screening procedure. In:
Proceedings of the Third National Research Conference on Pesticides.
NRCS, USDA. Hornsby,
A. G., R. D. Wauchope, and A. E. Herner (1995). Pesticide Properties in
the Environment. Springer-Verlage New York, Inc. Keisel,
W. G., R. A. Leonard, and F. M. Davis (1992). GLEAMS Users’ Guide. Ouyang,
D., and J. Bartholic (2001). The web-based application for soil erosion
prediction. An International Symposium – Soil Erosion Research for the
21st Century. January 3-5, 2001. Honolulu, HI. Ouyang,
D. (1999). Evaluation of the Windows Pesticide Screening Tool. Report to
Institute for Agriculture and Trade Policy. Ouyang,
D., J. Bartholic, and E. Hesketh (1998). Risk-based Analysis of
Pesticide Applications in Agricultural Cropland. In: Proceedings of
Watershed Management: Moving from theory to implementation. May 3-6,
1998. Denver, Co. pp 1089-1096. Ribaudo,
M. O., and A. Bouzher (1994). Atrazine: Environmental Characteristics
and Economics of Management. Agricultural Economic Report 699, USDA. Ribaudo,
M. O., and A. Bouzher (1994). Banning atrazine would increase costs to
farmers and consumers. Summary report #AER-699, USDA. Shaffer,
R. D. (1989). Evaluation of Leaching Prediction Models for Herbicide
Movement in the Soil Vadose Zone. PhD Dissertation, Michigan State
University. U.S.
Department of Agriculture, NRCS, 1983. Soil Survey of St. Joseph County,
Michigan. Vickery,
J. (1999). Decision Tool for Integrated Pesticide Selection and
Management. The Institute for Agriculture and Trade Policy. Minneapolis,
MN. Zacharias,
S., and C. D. Heatwole (1994). Evaluation of GLEAMS and PRZM for
prediction pesticide leaching under field conditions. Transactions of
ASAE. Vol. 37(2): 439-451. AcknowledgementsThis project was supported in part by the Michigan Corn Growers Association (MCGA) and Corn Marketing Program of Michigan (CMPM). We thank Rich Hodupp, Agricultural Agent in St. Joseph County (now in Kalamazoo County), for his technical assistance and coordination with local corn growers and crop consultants. We also thank our technical advisory team, especially Jon Silsby, a certified crop advisor in Michigan, Marcy Strefling, St. Joseph County Agricultural Agent, and Bruce MacKellar, Van Buren County Agricultural Agent, for their advice and feedback.
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