Aquatic Herbicide Applicator
Certification Training
Math/Calibraton
Ken Langeland
UF/IFAS
Agronomy Department
Center for Aquatic and Invasive Plants
Math Symbols
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Unknown value: a, b, ----- x, y, z
Equals: =
Multiply: x, (value 1)(value 2)
Example: 2x2=4, (2)(2)=4
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Divide: ÷, /
– Example: 4÷2=2, 4/2=2
Things You’ll Have to Do
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Determine areas
Determine volumes
Determine amount of herbicide
Determine sprayer output
Determine speed
Calibrate sprayer
KNOW!
•One mile = 5,280 ft
•One acre = 43,560ft2
•One gallon = 4 quarts, 8 pints, 128 oz
•Acre-feet=Average Depth x Surface Acres
Length: The distance between two points
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Units: inches (in), feet (ft), miles (mi)
Area: Surface enclosed by connected lines
Height
Width
Diameter
Length
Base
Area=length x width
Area=3.14 x (radius)2
(radius=diameter/2)
Area=1/2base x heigth
Units: square feet (in2, ft2, mi2, acres)
One acre=43,560 ft2
Area=Length x Width
Area=900 ft x 600 ft
Area=540,000 ft2
600ft
Example: Determine the area in acres of a
rectangular pond that measures 900 ft by
600 ft.
900ft
Convert answer to acres
Acres=540,000ft2÷43,560ft2
Acres=12.4
Area=3.14 x radius2
Area=3.14 x 902
Area=25,434 ft2
Acres=ft2/43,560
Acres=0.58
radius=diameter/2
radius=180ft/2
radius=90ft
180ft
Example: Determine the area in acres of a
round pond with a diameter of 180 feet.
Area=1/2base x height
Area=270ft/2 x 1200ft
Area=162,000ft2
1200ft
Example: Determine the area in square feet
of a triangular-shaped cove that has an
opening (base) of 270 ft and the distance
from the opening to the shoreline (height) is
1200 ft.
270ft
How Much Herbicide
• Pounds or gallons of herbicide per acre
• Concentration of herbicide in treated water
• Dilutions, percent solutions
Determining Amount of Herbicide Needed
Surface Area Applications
Herbicide needed=
recommended pounds per acre x surface area to be treated
or
recommended gallons per acre x acres to be treated
Example: How many pounds of granular herbicide are
needed to treat a rectangular pond that measures 120
ft by 40 ft if the herbicide label recommends
application of 120 pounds of product per acre.
Area=120ft x 40ft
Area=4,800ft2
Acres=4,800ft2÷43,560ft2
Acres=0.11
Pounds of herbicide=0.11 x 120=13.2
120ft
40ft
Area=3.14 x radius2
Area=3.14 x 4002
Area= 502,400ft2
Acres=502,400ft2 ÷ 43,560ft2
Acres=11.5
Gallons=2 x 11.5
Gallons=23
800ft
How many gallons of herbicide are needed to
treat a circular pond that measures 800 ft
across (diameter) if the herbicide label
recommends application of 2 gallons of product
per acre.
length
Depth w
id
t
h
Volume: Capacity measured in three dimensions
Volume=length x width x depth
Units: in3, ft3, acre-ft, pints, quarts, gallons
Acre-ft=surface acreage x depth (ft)
4ft
2ft
6ft
9ft
8ft
10 ft
9ft
12 acres
Acre-ft=surface acres x average depth
Acre-ft=12 acres x (9ft+10ft+9ft+8ft+6ft+4ft+2ft)/7
Acre-ft=82.3
Application Based on Herbicide
Concentration in Treated Water
• One acre-ft of water weighs 2,700,000 lbs or 2.7
million lbs
• Therefore, 2.7 lbs per acre-ft is 1ppm
• Lbs ai needed=recommended ppm x acre-ft x 2.7
• Lbs product=lbs ai ÷ % ai in product
• Gallons product needed=lbs ai ÷ lbs ai per gallon
Determine how much herbicide product,
which contains 2 lbs active ingredient (ai)
per gallon, to apply to a pond that is 1.6
acres in surface area and has an average
depth of 4 ft to result in a concentration of
0.37 ppm of the ai.
Acre-ft=average depth x surface acreage
Acre-ft=4ft x 1.6 acres
Acre-ft=6.4
Pounds a.i. needed=recommended x acre-ft x 2.7
Pounds a.i. needed=0.37 x 6.4 x 2.7=6.39
Product needed=6.39÷2lb ai/gal=3.2 gal
Determining Amount of Herbicide Needed
for Proportion or % Solution in Spray
Solution
• If recommendation is given as herbicide volume
per final spray volume
– Herbicide volume=(Given herbicide ÷
Given spray volume ) x spray volume
• If recommendation is given as percent solution
– Herbicide volume=Spray volume x (%
recommended ÷ 100)
Example: Four gallons of spray mix are to be
prepared for application in a backpack sprayer.
How many ounces of herbicide product should
be included in the final spray mix if the label
recommends using 2 gallons product in 75
gallons of spray mix?
Herbicide volume=(Given herbicide ÷ Given
spray volume ) x spray volume
Herbicide volume=(2 gal ÷ 75 gal) x 4 gal
Herbicide volume=0.1 gal
Ounces=0.1 gal x 128 oz/gal = 13.7
Four gallons of 1.5% spray mix are to be
prepared for application using a backpack
sprayer. How many ounces of herbicide
product should be included in the final
spray mix?
Herbicide volume=Spray volume x (% recommended ÷ 100)
Herbicide volume=4gal x (1.5% ÷ 100)
Herbicide volume=.06gal
Herbicide volume=.06gal x 128oz per gal
Herbicide volume=7.68oz
KNOW!
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GPA = GPM/Acres per minute
GPM = GPA x Acres per minute
GPA = Gallon sprayed/Acres treated
LBPA = PPM/Acres per minute
LBPM = PPA x acres per minute
Calibration for Mix Tank Application
1. Measure gallons per minute (GPM)
2.
3.
4.
5.
– Gallons sprayed ÷ Minutes elapsed
Determine acres per minute
– Acres per minute=Acres sprayed ÷ Minutes elapsed
Determine gallons per acre (GPA)
– GPA=GPM ÷ Acres per minute
Determine acres per tank
– Acres per tank=Tank volume ÷ GPA
Determine herbicide per tank
– Acres per tank x Product per acre
Determining Acres per Minute
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Acres per minute=Acres treated ÷ Minutes elapsed
Acres per minute=swath (ft) x speed (ft per min) ÷ 43,560
Acres per minute=swath (ft) x speed (mph) ÷ 495
Acres per minute=2 x swath (ft) x speed (mph) ÷ 1000
Example: How much herbicide should be
added to each full 100-gallon spray tank for
a system that delivers 5 GPM, covers a 16ft swath, and travels 218 ft per minute if the
recommended herbicide rate is 2 gallons
product per acre?
1. GPM given
2. Determine acres per minute
3. Determine GPA
4. Determine acres per tank
5. Determine product per tank
How much herbicide should be added to each full
100-gallon spray tank for a system that delivers 5
GPM, covers a 16-ft swath, and travels 218 ft per
minute if the recommended herbicide rate is 2
gallons product per acre?
Determine acres per minute:
Acres per minute=swath (ft) x speed (ft per min)/43,560
Acres per minute=16 ft x 218 ft per minute ÷ 43,560
Acres per minute=.08
Determine GPA:
GPA=GPM ÷ Acres per minute
GPA=5GPM ÷ .08 Acres per minute
GPA=63
Example: How much herbicide should be added to
each full 100-gallon spray tank for a system that
delivers 5 GPM, covers a 16-ft swath, and travels
218 ft per minute if the recommended herbicide
rate is 2 gallons product per acre?
Determine acres per tank:
Acres per tank=Tank volume ÷ GPA
Acres per tank=100 gallons ÷ 63 GPA
Acres per tank=1.6
Determine product per tank:
Product per tank=Acres per tank x Product per acre
Product per tank=1.6 Acres per tank x 2 gal per acre
Product per tank=3.2 gallons
Calibration for Direct Metering Systems
Determine required product per minute:
1. Determine acres per minute
2. Determine product per minute
Product per minute=Product per acre
(recommended) x acres per minute
Determine product delivered per acre for measured
product per minute:
1. Measure product delivered per minute
2. Determine acres per minute
3. Determine Product per acre
Product per acre=product per minute ÷ acres per
minute
Example: How many ounces should be withdrawn per
minute by a direct metering system to apply 1.5 gallons
of herbicide product per acre if swath is 15 feet and
speed is 105 feet per minute.
Determine acres per minute:
Acres per minute=swath (ft) x speed (ft per min)/43,560
Acres per minute=15 ft x 105 ft per min ÷ 43560
Acres per minute=.036
Determine product per minute needed:
Product per minute=Product per acre x acres per minute
Product per minute=(1.5 gal x 128 oz/gal) x .036
Product per minute=6.9 ounces
Example: If a direct metering system known
to deliver 8 ounces of herbicide product per
minute is used “as is” on a boat that treats
0.04 acres per minute, how many gallons of
herbicide product will be applied per acre?
1. Product per minute given
2. Acres per minute given
3. Product per acre=product per minute ÷ acres per minute
Product per acre=8 oz ÷ 0.04 acres per minute
Product per acre=200 oz
4. Convert ounces to gallons
Product per acre=200 oz ÷ 128 oz per gallon
Product per acre=1.6 gal
Calibrating for Granular or Pellet Applications
Determine how much product to deliver per minute for
given application rate and speed
1. Determine acres per minute
2. Determine Lb per minute required
Lbs per minute=lbs per acre recommended x acres per minute
Example
How many pounds of herbicide pellets should be
delivered per minute from a spreader if swath is 40
feet, acres per minute is determined to be 0.32 and
the label recommends 40 pounds per acre?
1. Acres per minute is given
2. Determine pounds per minute required
Lbs per minute=lbs per acre recommended x acres per minute
Lbs per minute=40 pounds x 0.32 acres per minute
Lbs per minute=12.8
BE CAREFUL !