environmental fate of herbicides and atrazine degradation ...herbicide degradation comments •new...
TRANSCRIPT
![Page 1: Environmental Fate of Herbicides and Atrazine Degradation ...Herbicide degradation comments •New EPA registrations usually require ^short herbicide half-life •Carryover issues](https://reader036.vdocument.in/reader036/viewer/2022071212/602825e7c917445a5c400305/html5/thumbnails/1.jpg)
University of Tennessee
Dr Tom Mueller
2019 IFCA Convention
January 28, 2019
Peoria, IL
Environmental Fate of Herbicides and
Atrazine Degradation in Illinois
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Most of the soils from Illinois used
in this research
were provided by Mark Bernards,
Western Illinois University
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Disclaimer• Views and Ideas expressed in this presentation do not
represent the views of the University of Tennessee
• Mention of a product does not constitute endorsement of that product to the exclusion of other similar products
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Outline of talk (30 minutes only)• Introduction
• Adsorption
• Degradation Processes• Chemical• Biological
• Factors affecting biological degradation
• Quantifying degradation
• Leaching, surface runoff (not covered, due to brevity)
• Enhanced Atrazine degradation in IL soils
• Questions (if time is available)
4
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Thomas C Mueller
Department of Plant Sciences
University of Tennessee
Knoxville, TN
Some slides used courtesy of Dr.
Scott Senseman
Herbicide Behavior in Soils
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Introduction
• Farmers do not like to use PREs• Rainfall needed to activate
• If persistent, can reduce flexibility in crops
• Cost more money, but do not always work
• But, using PREs targets the weeds at their most vulnerable growth stage (germination)
• Some PREs have no confirmed resistance (yet)
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Herbicide Adsorption to Soil• Adsorption
• Factors that affect adsorption
• What is a Kd?• Memorable demonstration
• CEC factors
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Chemical and Biological Degradation
• Terminology• Degradation – Breakdown of an organic compound
• Metabolites – Degradation products formed as a result of metabolic functions
• Sometimes called “daughter” metabolites…
• Important in product registrations….
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Biological Degradation• Dominant mechanism for degradation
• Involves microbial organisms (microbes) possessing enzymes that catalyze chemical reactions
• Microorganisms• Bacteria – Most numerous
• Actinomycetes – 5 to 20% of total bacteria
• Fungi – Less numerous
• Other – Plants, vertebrates, invertebrates
9Adapted from Paul and Clark, 1989.
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Factors Affecting Biological DegradationTemperature
10Paul and Clark, 1989.
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Factors Affecting Biological DegradationMoisture
11Paul and Clark, 1989.
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Quantifying Degradation
12
Take your observed
data and get a half-
life or DT 50
Bigger number
means herbicide
lasts longer
IL1
Days after Treament
0 10 20 30 40
Atr
azin
e in s
oil
(pp
b)
0
500
1000
1500
2000
2500
DT50 = 12.7
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What is Slow or Fast Degradation?
• Very Short < 5 days
• Short - 10 to 30 days
• Moderate - 30 to 90 days
• Long – 90 to 180 days
• Very long > 180 days
13
Based on J.B. Weber. 1993.
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Herbicide degradation comments
• “New” EPA registrations usually require “short” herbicide half-life
• Carryover issues more pronounced in northern climates (frozen soils over winter)
• Major environmental factor that changes year to year is soil moisture
• Drought can increase persistence
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Herbicide leaching
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Herbicide leaching
• For weed control, a small amount of “leaching” is often needed for weed control
• Factors affecting leaching into soil depths• A. heavy rainfall soon after application
• B. low CEC soil
• C. high water solubility of herbicide
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Herbicide Surface Runoff
• Factors affecting herb runoff• A. heavy rainfall soon after application
• B. sloping topography
• C. high soil erosion (herbicide moves with soil)
• D. higher herbicide use rates
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Herbicide in Soils
• Farmers do not like to use PREs• Rainfall needed to activate
• If persistent, can reduce flexibility in crops
• Cost more money, but do not always work
• But, using PREs targets the weeds at their most vulnerable growth stage (germination)
• Some PREs have no confirmed resistance (yet)
![Page 19: Environmental Fate of Herbicides and Atrazine Degradation ...Herbicide degradation comments •New EPA registrations usually require ^short herbicide half-life •Carryover issues](https://reader036.vdocument.in/reader036/viewer/2022071212/602825e7c917445a5c400305/html5/thumbnails/19.jpg)
Herbicide in Soils
•Questions?
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A national survey of the effect of previous atrazine use on enhanced
atrazine degradation in US soils •Thomas C. Mueller
•University of Tennessee, USA
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Thanks from Mueller
Alinna Umphres Ethan Parker
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Cooperating States• 16 states
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Soil Processing• Catalogued in upon receipt
• Stored at ~4C until use
• Soils saturated, allowed to drain
• ~ 5 g placed into 20 mL vials
• Each subsample fortified with atrazine in water
• Allowed to statically equilibrate at 22C
• -1, 0, 3, 7, 14, 21, 28, 42 DAT
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Champaign County
Top graph has > 5 years history of atrazine use
bottom graph has no atrazine use
IL12
Days after Treament
0 10 20 30 40
Atr
azin
e in
so
il (p
pb
)
0
500
1000
1500
2000
2500
DT50 = 3.4
IL13
Days after Treament
0 10 20 30 40
Atr
azin
e in
so
il (p
pb
)
0
500
1000
1500
2000
2500
DT50 = 26.9
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Carroll County
IL14
Days after Treament
0 10 20 30 40
Atr
azin
e in s
oil
(pp
b)
0
500
1000
1500
2000
2500
DT50 = 17.8
IL15
Days after Treament
0 10 20 30 40
Atr
azin
e in s
oil
(pp
b)
0
500
1000
1500
2000
2500
DT50 = 2.9
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McDonough/Henderson County
IL16
Days after Treament
0 10 20 30 40
Atr
azin
e in
so
il (p
pb
)
0
500
1000
1500
2000
2500
DT50 = 11.6
IL11
Days after Treament
0 10 20 30 40
Atr
azin
e in s
oil
(pp
b)
0
500
1000
1500
2000
2500
DT50 = 2.1
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Pike County
IL10
Days after Treament
0 10 20 30 40
Atr
azin
e in s
oil
(pp
b)
0
500
1000
1500
2000
2500
DT50 = 1.6
IL9
Days after Treament
0 10 20 30 40
Atr
azin
e in s
oil
(pp
b)
0
500
1000
1500
2000
2500
DT50 = 0.7
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Douglas County
IL8
Days after Treament
0 10 20 30 40
Atr
azin
e in s
oil
(pp
b)
0
500
1000
1500
2000
2500
DT50 = 20.3
IL7
Days after Treament
0 10 20 30 40
Atr
azin
e in s
oil
(pp
b)
0
500
1000
1500
2000
2500
DT50 = 5.2
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Washington County
NoHisDT50/HisDT50 =Enhancement Factor (EF)
IL1
Days after Treament
0 10 20 30 40
Atr
azin
e in
so
il (p
pb
)
0
500
1000
1500
2000
2500
DT50 = 12.7
IL 2
Days after Treament
0 10 20 30 40
Atr
azin
e in
so
il (p
pb
)
0
500
1000
1500
2000
2500
DT50 = 0.8
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EF <1.7
EF 1.7-3.5
EF >3.5
Soil Sample Sites
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Concluding Thoughts
➢Using atrazine many times reduces its
persistence in soil
➢Weed control from atrazine residual
expected to be less
➢POST atrazine still effective
➢Add tank-mix partners
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Concluding thoughts
➢PREs must be used.
➢No rainfall, no PRE activity
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Acknowledgments• This research was largely funded by the Tennessee Ag
Experiment Station
• Technical assistance by Alinna Umphres and Ethan Parker and several student workers
• Always read and follow all label instructions for all crop protection products
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August 5-8, 2019
Fort Collins, CO
Lory Student Center
Colorado State University
Fort Collins, CO 80523-8033
970-491-0229
Sponsored byTennessee Weed Science
Society
Tennessee Weed Science Short Course On Herbicide Modes of Action
and Resistance in WeedsIn Colorado
www.tnwss.org
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2019 TN short course Speakers
Steve Duke,USDA-ARS
Dale L. ShanerTodd A. Gaines , Colorado State University.
Patrick J. Tranel, University of Illinois
Franck Dayan, Colorado State University
Peter Sikkema,University of Guelph
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Questions?