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 AFM 91-19 / TM 5-629 / NAVFAC MO-314
24 May 1989
63
d. Determine the amount of herbicide re-
Feet per mile = 5,280
quired for each tankful by multiplying the area
Area sprayed = 75 x 5,280 x 40 x 0.017
in acres that each tankful will spray by the
= 6.18 acres
43,560
recommended application rate per acre.
Example:
Applied per acre = 12.5 = 2.0 gal
Tank capacity = 3 gal
6.18
Output = 27.6 gal
Area per tank = 3 = 0.1 acre
Herbicide needed per tank = 120 x 3 = 180
27.6
pt, or 22.5 gal
2.0
Recommendedrate per acre = 2 pt
b. Before spraying, equipment should be cali-
Herbicide needed per tank = 2 x 0.1 = 0.2
brated for swath width, volume and distribution
pt
of spray particles, and droplet size. Swath
widths and droplet distribution patterns may be
determined during calibration and at the applica-
9-6. Single-Nozzle Hand Sprayers. Fill the
tion sites by using water-soluble marking dyes
sprayer with water and apply it uniformly, in the
and rolls or sheets of white paper. The same
same manner the herbicide will be applied, to a
drift-retardant additive should be used during
1/100 acre area. An area measuring 43.6 feet by
the calibration as will be used during the actual
10 feet is suitable. Determine the gallons applied
application. A spray mixture of 8 ounces of
per acre, and the amount of herbicide required
nigrosine black per 50 gallons of water provides
per tankful, in the same manner as explained for
a distinctive pattern. With the boom and nozzle
boom-type hand sprayers.
dispersing systems employed on mist aircraft,
the effective swath width for uniform coverage
9-7. Aerial Sprayers:
is about the same as the wingspan, and should
a. To determine the rate of flow per acre and
not exceed 1.5 wingspan width.
per minute, put a known amount of spray or
water in the tank or mark the level in the tank.
9-8. Dry Granule Spreaders. To obtain accept-
Spray for a timed interval, for example 60
able accuracy, mechanical broadcasters or
seconds (0.017 hours), while flying straight and
spreaders for applying dry herbicide formula-
level at the speed that will be used for spraying.
tions must be calibrated with the actual material
Subtract the velocity of any headwind (or add
to be used and under the conditions that will be
any tailwind) from the airspeed to obtain the
encountered in the field. Calibration is a simple
groundspeed. When the airplane lands, either
procedure when calibration pans are available to
measure the liquid remaining in the tank or
catch the material for weighing during trial runs.
measure the amount required to refill the tank
A more complicated and wasteful procedure is
to the same level. Compute the rate of spraying
required for spreaders that are not so equipped.
and the amount of herbicide needed as follows:
a. Mechanical Spreaders With Calibration
Area sprayed =
Pans:
groundspeed (mi/h) x ft per mile
x swath width x time in hours
(1) Use a calibration pan, or, if one is not
43,560 ft2 per acre
available, make one by cutting house gutter to
the proper length, blocking the ends, and hang-
Applied per acre = gal used
ing it under the spreader with string or wire.
acres sprayed
(2) Fill the spreader at least half full of the
Herbicide needed per tank =
material to be applied. With the calibration pan
tank capacity in gal x application rate per acre
in place, push or pull the spreader at the speed
gal spray per acre
that will be used during application. Do this
over terrain that is typical of that which will be
Example:
treated, and go far enough to cover 1/100 acre,
Groundspeed = 75 mi/h
or 435.6 ft2. For a spreader 3 feet wide, the
Width of effective swath = 40 ft
distance should be 435.6 divided by 3, or 145.2
Time sprayed = 60 sec, or 1 min, or 0.017
ft. For a spreader 8 feet wide, the distance
hr
would be 435.6 divided by 8, or 54.45 ft.
Gal used = 12.5
(3) Weigh the material in the calibration
Tank capacity = 120 gal
pan and multiply the weight by 100 to find the
Recommended rate per acre = 3 pt
amount applied per acre.
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