clemson landscape professional certificationmedia.clemson.edu/public/turfschool/wq and...
TRANSCRIPT
2/12/16
1
Dara Park, Ph.D., Clemson University
Carrier Water Quality Influences Pesticide Efficacy
Dara Park [email protected]
Clemson Landscape Professional CERTIFICATION
¨ COMING THIS FALL ¨ Completely online ¨ MODULES:
ü General information ü Tree care ü Water ü Herbaceous plants & shrubs care ü Plant identification ü Turfgrass ü IPM ü Calibrations and Maintenance ü Low Impact Development Strategies
Learning Objectives LO1: What influences water composition? LO2: Common water quality issues that influence pesticide efficacy. LO3: How to measure pH.
2/12/16
2
What influences water quality
FACTORS • Mineralogy • Climate • Weathering Management practices!
• Use of acid-forming N fertilizers • Application of chemicals • Soil disturbance • Irrigation practices
Minerals influences water chemistry • Naturally occurring due to release of Ca, Mg, Fe and HCO3 from carbonate-rich sedimentary rock.
Sources of components
2/12/16
3
Sources of components
What influences water quality?
• Reliance on lower quality water sources due to increased pressure on potable water sources
Increased Use of Alternative Water
• Pathogens • Elevated nutrient concentrations • Heavy metals • Suspended solids • Dissolved organic matter
2/12/16
4
Common Issues with Water Quality and Pesticide Efficacy
• pH • Hardness (presence of Ca, Mg and Fe) • Alkalinity • Iron • Turbidity
What is pH?
• AKA Per hydrogen, Power of the hydrogen, potential of hydrogen
• Concentration of H+ ions in water • Water equilibrium: H2O <=> H+ + OH-
Measure of the [H+] and [OH-]
Logarithmic scale: pH of 6 is 10X more H+ than pH=7
pH of 5 is 100X more H+ than pH=7
2/12/16
5
<< acidic << >> alkaline >>
neutral = 7
Examples of a pH litmus strips.
Example of a pH meter.
2/12/16
6
Common pH’s
Driven by biological activity: • photosynthesis • aerobic respiration • anaerobic respiration
Diurnal changes in water pH
May June July Aug pH: 6.5 7.2 7.8 8.5
Example of seasonal change in water pH
2/12/16
7
Example: Hydric pine flatwoods
Plant community influences pH
Where to purchase meters & litmus strips • Many pool and aquarium stores sell pH kits.
• Online: www.forestry-suppliers.com www.coleparmer.com www.amazon.com www.fishersci.com www.benmeadows.com
Monitoring pH • Most turfgrasses want soil pH ~5.5-6.5 • Optimum pH is species dependent
• If out of range, indicates other problems • Nutrient availability • Hardness • Bicarbonates • Salinity
2/12/16
8
pH effect on element availability
Pesticides and pH • Most pesticides are stable at pH 4 to 6. • Some pesticides “decompose” pH > 7.
-alkaline hydrolysis
Pesticides and pH: alkaline hydrolysis Postemergent herbicides are weak acids: release H+ ions in water
• Glyphosate (Roundup) • Bentazon (Basagran) • Carbamates • 2,4-D (amine form)
• Partially dissociate when mixed with high pH water • The part that does not dissociate is readily absorbed by leaves • The part that is dissociated is – charged and can bind with cations.
• antagonize most of the time • Work best at pH of 4-6 Exception: Sulfonylurea herbicides: Certain herbicides are susceptible to acid hydrolysis Keep the pH above 6.0
2/12/16
9
Alkaline hydrolysis • Loss of pesticide efficacy: pesticide is chemically denatured. -examples:
-Dylox insecticide (half-life 4 days in pH 8.0) -Polyoxin D (Endorse) fungicide -Thiophanate methyl (Cleary’s 3336)
Always refer to product MSDS and label for
pH stability information.
Always check the MSDS…
…and the label.
2/12/16
10
Case Study
0
2
4
6
8
10
4 5.5 7 8.5 10 Untr.Water Carrier pH
Dol
lar
Spot
(#
Infe
ctio
n C
ente
rs)
Bellewood GC, creeping bentgrass (~fairway), July 11, 2006.
b b b b
Banner MAXX @ 0.5 fl oz/M
b
a
0
10
20
30
40
50
5 7 9 Untr.Water Carrier pH
Dol
lar
Spot
(#
Infe
ctio
n C
ente
rs)
Rutgers, creeping bentgrass (~green), July 19, 2007.
b b b
Banner MAXX @ 1 fl oz/M
a
2/12/16
11
0
2
4
6
8
10
4 5.5 7 8.5 10 Untr.Water Carrier pH
Dol
lar S
pot
(# In
fect
ion
Cen
ters
)
Bellewood GC, creeping bentgrass (~fairway), July 11, 2006.
d d d
b
Daconil Ultrex @ 1.8 oz/M
ab a
0
10
20
30
40
50
5 7 9 Untr.Water Carrier pH
Dol
lar
Spot
(#
Infe
ctio
n C
ente
rs)
Rutgers, creeping bentgrass (~green), July 19, 2007.
b b b
Daconil Ultrex @ 3.2 oz/M
a
• A way to compare how long pesticides take to break down. • A half-life is the period of time it takes for one-half (50% hydrolysis) of the amount of pesticide in the water to degrade.
• Each half-life that passes reduces the amount of pesticide in the water one-half: 100% to 50% to 25% to 12.5%, etc.
Half-life
Chemical pH =6 pH= 7 pH=8 pH=9
Carbaryl 100-150 days 24-30 days 2-3 days 1-3 days
Captan 8 hours 10 min 2 min
Diazinon 70 days 29 days
Chlorpyrifos 35 days 22 days
trichlorfon 3.7 days 6.5 hours 63 min
2/12/16
12
Suitability pH 3.5-6.0 Satisfactory for most spraying & can be
stored for 12-24 hrs. Not suitable for sulfonyl urea herbicides.
6.1-7.0 Adequate for immediate spraying. Short
term storage only (1-2 hrs). >7.0 Add buffer or acidifier.
What can you do? • acids • chelating agents • surfactants • ammonium sulfate
Buffering agents: will resist change in pH Spray immediately after mixing.
ALWAYS CHECK THE LABEL!
Plants can uptake cationic and anionic N chemical species.
• Two main forms: • NO3
-
• NH4+
Roots interior rhizosphere
NO3-
HCO3- and or OH-
(nitrate ion)
H+
2H+
NH4+
NH4+
(ammonium ion)
Form of N taken up by plants influences soil pH
2/12/16
13
Acid injection: principles
Acids that are typically used include: • Citric • Nitric • Phosphoric • Sulfuric
H+ (from acid) + HCO3- (in the water) è CO2 é + H2O
Comparison of acids Acid Amount to add for
each meq/L of alkalinity to result in water pH=5.8
Relative Cost
Relative Safety
Citric (granular) 9.1 oz /1000 gal $$$ minor
Citric (liquid) 14.5 fl oz / 1000 gal $$$ minor
Nitric 6.6 fl oz / 1000 gal $ severe
Phosphoric 8.1 fl oz / 1000 gal $$ moderate
Sulfuric 11.0 fl oz / 1000 gal $ severe
• High mineral content (especially Ca, Mg, and Fe) in the water • Reported as equivalent quantity of CaCO3
Water hardness
Classification Mg/l or ppm Grains / gal
Soft 0 – 17.1 0 – 1 Slightly hard 17.1 – 60 1 – 3.5 Moderately hard
60 – 120 3.5 – 7
Hard 120 – 180 7 – 10 Very hard > 180 > 10
2/12/16
14
• Ca and Mg bind with HCO3 to form insoluble salts • Impacts soil pH • Forms scales changing flow rates
Water hardness
These cations attach to – charged dissociated herbicide molecules (due to high pH) and form insoluble salt precipitates. Examples: • Extremely hard water (600 ppm) can almost completely render 2,4-D at the low rate (4 -8 oz/A) ineffective
• Dicamba • Glyphosate • Clopyralid (Lontrel)
Water hardness
Use ammonium sulfate: • to keep pH low, • SO4 binds up with the hard minerals
Organic acids (ex. Citric): • a weak acid in which the conjugate base reacts with water cations. • adds H+ ions too (lowers pH)
In both cases, add to tank before the herbicide.
Common ways to counter water hardness
2/12/16
15
Is dilution the solution? NO
1 hard water ion can bind up ≥ 2 herbicide molecules
Instead: Decrease the volume of water used to apply • Lower volumes means less antagonistic cations present. • Use maximum label rates AS A LAST RESORT • Non-ionic surfactants enhances herbicide efficacy but does not overcome the antagonism!
Common ways to counter water hardness
• The concentration of CO32-
and HCO3- in water.
• bicarbonate (pH < 8.3, HCO3) • carbonate + bicarbonate (pH > 8.3, CO3 + HCO3)
Water alkalinity
• Buffering capacity:
• how well it resists or causes a change in water pH. • measure of the ability of water to change pH of growing media • high alkalinity will increase soil pH over time
Water alkalinity
2/12/16
16
High alkalinity indicators
Alkalinity and pesticides
• Certain herbicides are less effective at high concentrations (>300 ppm)
• Example: • 2,4-D amine: >500 ppm
Alkalinity treatment options
• Reduce water volume • Reduce lime substrate
amendment rate • Use an acid reacting
fertilizer • Acid injection • Reverse osmosis or
deionization Alkalinity calculator – < http://extension.unh.edu/Agric/AGGHFL/Alkcalc.cfm>
2/12/16
17
Acid injection
Bailey and Bilderback. 1998. Alkalinity. NCSU HIL #558
Iron (Fe)
• Normal Range: 0-0.3 ppm
• >0.2 ppm stimulate iron reducing bacteria
• > 0.3 ppm = stains • > 5 ppm, begin to have
films on plants
• 6th most abundant element in the universe, 4th in the earth’s crust!
Iron • Bacteria slime clog boreholes, pumps and fittings • Rust clog nozzles, filters, and lines. • Brown leaf coatings reduce photosynthesis
• Minimal problem for turfgrasses but is a problem for ornamentals
2/12/16
18
Managing Iron
Dependent on type of problem that exists • Keep pH greater than 7.0 • Aeration, then sediment filtration • sediment filtration, then water softener • KMnO4 , then sediment filter • Chlorination, then sediment and carbon filtration
Turbidity
Suspended Solids • organic particulate matter • fine mineral fraction • animal and plant material
Organic matter benefits and potential problems
2/12/16
19
Adsorption
Portion of the label of RoundUp Pro:
Certain pesticides bind with soil (ex. Many post-emergent herbicides)
Microbial degradation
• Degradation of pesticide by microorganisms (bacteria, fungi, algae, protozoa, etc).
• Microbial degradation is a natural process, and at most times it is beneficial to the environment. The end products are mostly CO2, H2O and other organic and inorganic matters.
Turbidity Kd and Koc: Coefficients that deescribe the binding strength of herbicides
• The ratio of herbicide bound to the soil when mixed with a water/soil slurry. Kd: soil sorption coefficient • Dependent on soil characteristics
Koc: soil organic carbon coefficient • independent of soil type
2/12/16
20
Some Koc values
Herbicide Koc (mg/L) Turbidity effect Glyphosate 24,000 Y Paraquat 1,000,000 Y 2,4-d amine 100 N Dicamba 2 N
The higher the number, the more tightly bound, less effective
Test & Manage for turbidity
Options: • Wait until clear • Use a filter • Determine best place in water
column to withdrawal • Blend sources • Use an additive to precipitate
Quick test: If you can see a quarter in the bottom of a 5 gal bucket of carrier water, then should be ok.
Saline water
• Salts in irrigation water. A problem more along
the coast. • Atlantic Intracoastal Waterway • Tidally influenced creeks, streams, and rivers • Saline aquifers
• Can be assessed as water hardness too • All glyphosate labels recommend adding
ammonium sulfate (AMS).
2/12/16
21
Measuring Salinity Electrical Conductivity (EC)
Normal range: 0-0.78 dS/m 1dS/m = 1mmhos /cm = 1000 µS/cm
Total Dissolved Salts (TDS) Normal range: 0-500 ppm
Case Study: Irrigating with salt water affects the biology of soil-inhabiting insects
• Can subsurface drip irrigation with salt water affect: • the life history of insects? • development? • survival rate?
• Salt concentrations: • fresh water ( 0.1 ds m-1) • saline water (~5 ds m-1)
• Insects investigated: • ground beetles – surface predator • scarab beetle – underground organic feeder • billbug – underground root feeder
Saline irrigation water did not affect biology of surface feeder
0
0.5
1
1.5
2
2.5
3
5/15/2007
5/29/2007
6/12/2007
6/26/2007
7/10/2007
7/24/2007
8/7/2007
8/21/2007
9/4/2007
9/18/2007
Sampling dates
gro
un
d b
eetl
es
freshsaline
2/12/16
22
Saline irrigation water did not affect the biology of underground OM feeder
02468101214161820
5/15/2007
5/29/2007
6/12/2007
6/26/2007
7/10/2007
7/24/2007
8/7/2007
8/21/2007
9/4/2007
9/18/2007
Sampling dates
Sca
rabs
freshsalt
Saline irrigation water affected biology of root feeders
00.20.40.60.81
1.21.41.61.82
5/15/2007
5/29/2007
6/12/2007
6/26/2007
7/10/2007
7/24/2007
8/7/2007
8/21/2007
9/4/2007
9/18/2007
Sampling dates
# b
illb
ug
s
freshsalt
Summary
Before applying a pesticide: • Check the label and MSDS for water quality compatibility issues. When in doubt call the company rep. • Always test water pH before you add pesticide • If the carrier water needs to be adjusted, do it before adding the pesticide • Keep a log what you do.
Same goes for the irrigation water if needing to irrigate the pesticide in!