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 62
AFM 91-19 / TM 5-629 / NAVFAC MO-314
24 May 1989
b. Sprayer and spreader outputs should be
number of acres each tankful will spray. Multi-
calibrated for each particular treatment opera-
ply this by the amount of herbicide recom-
tion. A good procedure is to make initial adjust-
mended per acre.
ments to suit the machine and job requirements,
and then to make a trial run to determine the
Example:
machine's actual output. The herbicide mixture
Tank capacity = 55 gal
should then be prepared accordingly. The cali-
Output = 6.2 gal/a
bration should be repeated frequently to guard
Recommended rate per acre = 2 pt
against nozzle orifice wear and other factors that
Herbicide needed per tank = 55 x 2 =
affect performance. This is especially important
17.7 pt, or 2.2 gal
6.2
when wettable powders and abrasive sprays are
g. In some row plantings, only narrow
used.
bands are sprayed, centered over each row, and
c. There are many methods of calibrating a
the rate of treatment is in terms of the area
sprayer. A method is given here for each of the
actually treated and not acres of the crop. The
basic types of ground and aerial sprayers. Equiv-
rate of treatment is easily converted to a rate per
alent measures are shown in attachment 30.
acre of crop, however, if this is needed to
calculate costs. With a 36-inch row spacing, if a
9-4. Boom-Type Power Sprayers:
12-inch band is treated at a rate of 1.5 lb/a, the
a. Determine that all nozzles are discharging
amount of chemical used per acre of cropland is
uniformly by spraying water through them at a
12 x 1.5 = 0.5 lb.
36
uniform pressure and catching the discharge
from each nozzle in a separate container. If the
amount of discharge varies widely, replace all
9-5. Boom-Type Hand Sprayers:
nozzle tips that give a much larger or smaller
a. Fill the sprayer to a marked point with
discharge.
water, maintain a constant tank pressure, and
b. Place the sprayer on level ground, and fill
spray while walking steadily for 330 feet at the
the spray tank completely with water. Adjust the
pace that will be used when spraying. Multiply
pressure of the sprayer to what it will be when
330 by the width of the spray swath in feet to
used in the field.
obtain the area sprayed, and divide this by
c. Drive and spray exactly one-eighth of a
43,560 (the number of square feet in an acre) to
mile (660 ft) in a field or along a road,
obtain the fraction of an acre sprayed.
ditchbank, or other typical spray area at the
b. Measure the amount of water required to
speed that will be used when spraying, usually 3
refill the tank to the marked point. Convert
to 5 mi/h. Begin measuring the distance at the
pints or quarts to gallons by dividing by 8 or 4,
point where the spraying begins. Mark the
respectively, and divide the gallons required by
throttle settings and the gear used, or make a
the fraction of an acre sprayed to find how
note of the speed, and use this when spraying.
many gallons were applied per acre.
d. Shut off the spray, return the sprayer to its
Example:
original position on level ground, and measure
Two nozzle boom, 20 inch spacing =
the water that is required to refill the tank (a
swath width of 40 inches or 3.33 ft
quart jar is satisfactory).
Water required to refill = 5.5 pt, or 0.69
e. Calculate the output per acre as follows:
gal
Gallons per acre = Number of quarts used x 16.5
Area sprayed = 3.33 x 330 = 0.025 acre
width of spray swath in feet
43,560
Example:
Applied per acre = 0.69 gal = 27.6 gal
Water used = 7.5 qt
0.025
Spray swath width = 20 ft
c. If too much spray is applied, walk faster or
Output per acre = 7.5 x 16.5 = 6.2 gal
use smaller nozzle tips. Do the opposite to
20
obtain more volume. For larger volumes, use
nozzle tips that have larger orifices. Small
f. To determine the amount of herbicide
changes in volume can be obtained with changes
needed in each tankful, divide the number of
in pressure, but too low a pressure gives a poor
gallons the tank holds by the number of gallons
spray pattern, and too high a pressure results in
per acre that your sprayer applied. This is the
fine droplets prone to drift.
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