Slide Presentation

TITLE    (click title to view slides)

Tim R. Murphy
The University of Georgia
Crop and Soil Sciences

• Slide Presentation (PowerPoint, 4.4 MB)

  1. Environmental Fate of Turfgrass Herbicides
  2. Public Concerns
  3. "Public Concerns" About Chemicals
  4. Turf Herbicide Concerns
  5. Family Circle Magazine Quote
  6. Theoretical Rate Needed for Weed Control
  7. Fate of Herbicides Applied to Turf
  8. Fate of Herbicides Applied to Turf
  9. Environmental Fate of Herbicides
  10. Herbicide Fate in the Soil
  11. Herbicide-Chemical Properties
  12. Soils - Solid Phase
  13. Soils - Colloidal Phase
  14. Soils - Gas & Liquid Phase
  15. Soils - Living Phase
  16. Microbial Degradation
  17. Herbicide Dissipation
  18. Herbicide Adsorption
  19. Soil Factors: Cation Exchange Capacity (CEC)
  20. Herbicide Particles in Soil
  21. Soil Factors: Organic Matter and Texture
  22. Amount of atrazine required to reduce giant foxtail growth by 50% at varying OM levels.
  23. Water Movement
  24. Factors That Affect Leaching
  25. Relative Movement of Herbicides
  26. Mobility of Preemergence Herbicides in Soil
  27. Mobility of Postemergence Herbicides in Soil
  28. Volatility
  29. Volatility
  30. Preemergence Herbicide Water Solubility and Relative Volatility
  31. Postemergence Herbicide Volatility
  32. Photodecomposition
  33. Herbicide Persistence - Soil
  34. Herbicide 1/2 Life
  35. Preemergence Herbicides - Avg. t-1/2
  36. Preemergence Herbicides - Avg. t-1/2
  37. Postemergence Herbicides - Avg. t-1/2
  38. Postemergence Herbicides - Avg. t-1/2
  39. Postemergence Herbicides - Avg. t-1/2
  40. Herbicide Degradation
  41. Herbicide Persistence (75% degradation)
  42. Herbicide Leaching Potential Index
  43. HLP Index
  44. HLP Index - Preemergence
  45. HLP Index - Postemergence
  46. Soil Leaching Potential - SLP
  47. SLP
  48. SLP
  49. Herbicide Selection with HLP/SLP Matrix
  50. Best Management Practices - BMPS
  51. BMPS (continued)
  52. SU Herbicide Lateral Movement
  53. SU Herbicide Lateral Movement
  54. SU Herbicide Lateral Movement
  55. SU Herbicide Lateral Movement
  56. SU Herbicide Lateral Movement
  57. Kerb
  58. Can SU Herbicides Move?
  59. 0 Residue Ain’t Possible!!!
  60. Risk Communication
  61. Facts

  1. Environmental Fate of Turfgrass Herbicides Tim R. Murphy The University of Georgia Crop and Soil Sciences
  2. Public Concerns Health Quality of Life Environment Nuclear and Toxic Waste Chemicals vs. Natural Right-to-Know
  3. “Public Concerns” About Chemicals Cause cancer Not well tested Harm animals Last forever Not “natural” Used carelessly Contaminate water Any amount is dangerous
  4. Turf Herbicide Concerns Last forever Contaminate water Affect human health Sterilize soil Use is not needed Kill all desirable organisms Degrade the environment
  5. “For the price of a green lawn, we are poisoning our children.” Family Circle magazine, 1991
  6. Fate of Herbicides Applied to Turf Water solubility - the extent to which a pesticide will dissolve in water Sorption by clay colloids and organic matter Adsorption - binding of a herbicide to the surface of a soil particle . Absorption - Penetrates into plant tissue Microbial degradation - influenced by herbicide concentration, temperature, moisture, pH, oxygen, microbial population
  7. Fate of Herbicides Applied to Turf Chemical degradation and photodecomposition Hydrolysis, oxidation, reduction, and photodecomposition under field conditions Volatilization and evaporation - Loss due to an increase in temperature, vapor pressure, and wind movement. Plant uptake and metabolism - roots, shoots, leaves
  8. Environmental Fate of Herbicides
  9. Herbicide Fate in the Soil Herbicide Chemical Characteristics Soil Physical-Chemical Characteristics
  10. Herbicide-Chemical Properties Ionic State (cation, anion, basic or acidic) Water Solubility Vapor pressure Hydrophobic/hydrophilic Partition coefficient Chemical, photochemical, microbial sensitivity
  11. Soils - Solid Phase Sand - 0.2 to 2.0 mm Silt - 0.002 to 0.2 mm Clay - < 0.002 Organic matter - decaying plant and and animal residue
  12. Soils - Colloidal Phase Consists of clay and organic matter Huge surface area Negatively charged Anions (-charge) repelled Cations (+charge) attracted Primarily responsible for binding herbicides
  13. Soils - Gas & Liquid Phase Gas - oxygen, carbon dioxide, others Liquid - water (with dissolved molecules, ions, etc.)
  14. Soils - Living Phase Microorganisms - bacteria, actinomycetes, fungi Algae Vertebrates and Invertebrates Microorganisms degrade herbicides
  15. Microbial Degradation Higher with high microbial populations May use as food source, or just degrade the herbicide Faster under warm, moist conditions Slower under cool, dry conditions
  16. Herbicide Dissipation Dosage Affinity for binding Water solubility, Leaching Microbial and chemical degradation Volatilization Photodecomposition Plant Uptake and Metabolism
  17. Herbicide Adsorption Soil texture coarse, sandy soils have few binding sites Permeability highly permeable soils low in CEC have few binding sites Soil OM and clay content increase binding Excessive moisture interferes with binding
  18. Soil Factors Cation Exchange Capacity (CEC) soils ability to adsorb positively charged compounds fine-textured, high-organic matter soils have larger CEC’s than coarse, low-organic matter soils paraquat
  19. Soil Factors Organic Matter and Texture most important for soil applied herbicides Indirectly influences all processes that affect herbicides!! the greater the organic matter and clay content, the greater adsorption of herbicides
  20. Amount of atrazine required to reduce giant foxtail growth by 50% at varying OM levels. Parochetti 1973
  21. Water Movement Surface runoff Leaching Capillary action
  22. Factors That Affect Leaching
  23. Relative Movement of Herbicides
  24. Mobility of Preemergence Herbicides in Soil
  25. Mobility of Postemergence Herbicides in Soil
  26. Volatility Volatility - physical change of a liquid or solid to gas.
  27. Volatility Related to vapor pressure Increases at high air temperatures Increases under high soil moisture conditions Higher on coarse textured, sandy soils
  28. Preemergence Herbicide Water Solubility and Relative Volatility
  29. Postemergence Herbicide Volatility
  30. Photodecomposition Photodecomposition - Breakdown of the herbicide by sunlight (primarily UV portion).
  31. Herbicide Persistence - Soil Usually expressed as the half-life (t1/2).
  32. Herbicide ˝ Life Amount of time it takes a herbicide to reach one-half (t1/2) of the originally applied concentration. Expressed in days, wks, months, yrs.. 1.0 lb. Ai/acre 0.5 lb. Ai/acre
  33. Preemergence Herbicides – Avg. t-1/2
  34. Preemergence Herbicides – Avg. t-1/2
  35. Postemergence Herbicides – Avg. t-1/2
  36. Postemergence Herbicides – Avg. t-1/2
  37. Postemergence Herbicides – Avg. t-1/2
  38. Herbicide Degradation
  39. Herbicide Persistence (75% degradation) E E E E B B B B E
  40. Herbicide Leaching Potential Index HLP – developed by Warren and Weber, NCSU Factors considered include: Binding ability Persistence (t-1/2) Application rate Amount that penetrates turf canopy and reaches soil Soil pH, O.M., type
  41. HLP Index Low potential for leaching - > 10.1 Moderate potential - 1.0 to 10.0 High potential - < 1.0
  42. HLP Index – Preemergence
  43. HLP Index – Postemergence
  44. Soil Leaching Potential - SLP Texture, O.M. and pH have greatest impact on herbicide leaching Clays retard movement, sands increase High O.M. retards, low O.M. increases Acidic pH increases degradation Neutral to alkaline pH decreases degradation, and can increase movement potential
  45. SLP S, LS, SL, L, SiL, L: 10 SCL, CL, SiCL: 6 SiC, SC: 3 C or muck: 1 S= sand, L = loam, Si = silt, C = clay
  46. SLP Can be calculated for each soil type Based on texture and pH 0 to 91 cm Based on O.M. in upper 15 cm High soil leaching potential: > 131 Moderate: 90 to 130 Low: < 89
  47. Herbicide Selection with HLP/SLP Matrix
  48. Best Management Practices - BMPS Use herbicides with low HLP Indices on high SLP soils Train employees on proper application techniques Spot treat if possible Follow label Be aware of any water advisory statements
  49. BMPS (continued) Consider mixing/loading pads, with spill containment Do not mix or apply within 100 ft. of a well head Prevent back-siphoning Calibrate sprayer Establish buffer (non-treated areas)
  50. SU Herbicide Lateral Movement Griffin, GA Lateral runoff facility 5% uniform slope Wobbler irrigation heads 1.25 inches per hour Tifway bermudagrass 0.5 inch clip height
  51. SU Herbicide Lateral Movement Plots 25 ft. long Lower 10 ft. fall-seeded with perennial ryegrass Upper 15 ft. not overseeded January 22, 2004, applied to dormant bermuda Monument at 0.33 and 0.56 oz./acre Manor at 0.5 oz./acre TranXit at 2.0 oz./acre Kerb at 2.0 lbs./acre
  52. SU Herbicide Lateral Movement Before application Applied 2.5 inches irrigation (2 hrs), 37% saturation Waited ~ 1hr, until foliage dried Applied herbicides Waited ~ 1hr, until foliage dried Applied 2.5 inches irrigation (2 hrs) Applied 0.5 inch irrigation water 24 HAT
  53. SU Herbicide Lateral Movement WHAT HAPPENED?? Kerb – moved 8 ft. (76% injury) Monument 0.33 oz. – 0.7 ft (3%) Monument 0.56 oz. – 3 ft. (14%) Manor 0.5 oz. – 0.7 ft. (1) TranXit 2.0 oz – 0.6 ft. (1) NOTE: No significant injury occurred until 48 DAT
  54. KERB Kerb Great for Poa Hell on ryegrass
  55. Can SU Herbicides Move? Yes, if: Surface film of water present at application Irrigation or rainfall immediately after application Not watering after foliage has dried Dew re-suspends and can cause tracking (prevent by watering in) Improperly adjusted irrigation heads
  56. 0 Residue Ain’t Possible!!! 1 ppm = one second in 12 days 1 ppb = one second in 32 years 1 ppt = one second in 32,000 years 1 ppq = one second in 32,000,000 years 1.0 lb. Ai/acre = 1.0 ppm in upper 3 inches
  57. Risk Communication “Everything is Poison. There is nothing without poisonous properties. The dose differentiates a remedy from a poison.” Philippus Aureolus Theophrastus Bombastus von Hohenheim 1493-1541 Better known a Paracelsus
  58. Facts 30 yrs added to lifespan in 20th century 8 yrs added since use of pesticides only 37% of land farmed in 1950 is cultivated today Dennis Avery, Hudson Institute, Wall Street Journal, August 12, 1999 deer, turkey, geese populations increasing in GA
  59. Thank you very much!!