Band spraying preemergence herbicides

U.^JIVERSITY OF
AT ll-i"^°'2 LIBRARY
AT URBANA CHAMPAIGN

AGRICULTUR'^

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UNIVERSITY OF /LLINOKJ
AGRICULTURE LIBRflRy

BAND SPRAYING
preemergence herbicides

JNIVERSITY OF ILLINOIS AT URBANA-CHAMPAIGN
COLLEGE OF AGRICULTURE
'-OOPERATIVE EXTENSION SERVICE

SPRAYING A PREEMERGENCE HERBICIDE
on the soil surface at planting time can provide eco-
nomical control of weeds that are sometimes difficult
to control with cultivation. Band spraying a strip 12 to
14 inches wide over the row can be particularly helpful
and less expensive than broadcast application.

Band applications should always be supplemented
with timely cultivation for complete weed control.

This circular suggests ways to help you properly
apply a liquid preemergence herbicide in a band over
the row. This is usually done while planting with a
band-spray attachment on the planter, but it may also
be done shortly after planting with a separate spraying
operation.

Equipment for band spraying

Commercial attachments for planters can be pur-
chased with the planter or the equipment can be added
later. If you have a field sprayer, especially a tractor-
mounted one, much of it can be adapted for use in
band spraying. Figure 1 is a schematic diagram of the
necessary equipment and how it can be arranged. It is
especially important that the spray nozzles have a uni-
form application rate across the band. If wettable
powders are to be used, it is essential that they be
properly mixed and then kept well agitated. A sepa-
rate line, which is not shown in Figure 1, from the
pressure side of the pump to a jet agitator is probably
most practical for agitation unless mechanical agitation
can be provided. The pump should have at least 6 to 8
gallons per minute excess flow over that needed at the
nozzles to provide adequate hydraulic agitation.

Amount of spray solution to apply

Preemergence herbicides for band spraying are com-
mercially available as liquid formulations and as wet-
table powders. Recommended amounts of a commercial
product to apply per acre can be obtained from the
container label, from your herbicide supplier, or from
your county extension adviser. The commercial prod-
uct must be mixed with water to form a spray solu-
tion or suspension. The recommended broadcast rate
for liquid formulations of most herbicides is 10 to 20
gallons of solution per acre. Application rates that are
too low can result in clogging of nozzles and screens
and in excessive drift because of small particles.

Use the proper nozzle tips
and measure output frequently

Several different types of nozzles and nozzle tips are
available for spraying herbicides. For band spraying
a nozzle with an even spray tip should be used. An
even spray tip provides uniform distribution across the
entire band width. Hollow cone or regular flat fan
nozzle tips should not be used for band spraying.

Select a nozzle tip size that will give the proper flow
rate at a pressure lietween 20 and 40 pounds i^er
square inch (20 to 30 is suggested). If the pressure
is increased above 30 pounds per square inch, the spray
particle size decreases and turbulence increases so the
spray particles drift more. Tf this reduces the amount
of herbicide in the band, decreased weed control could
be the result.

If you select your nozzle on the l^asis of 25 pounds
of pressure per square inch, you will have some leeway
in making the final pressure adjustment. It is better
to use larger nozzle tips or reduce speed to increase
the rate of application rather than to increase pressure
beyond a maximum of 40 pounds per square inch. To
double the rate of application without changing nozzle
tips or speed, you would have to make the pressure
about four times as great.

Table 2 can be used to select and check nozzles
for different combinations of ground speed and appli-
cation rates. The gallons per minute values are useful
for selecting nozzles from manfacturers' catalogs and
the ounces per minute values are useful for checking-
nozzles on your sprayer.

Example: You want to apply a herbicide in a 13-
inch band at a rate equivalent to 20 gallons per acre
broadcast while planting at a speed of 4 miles per hour.
Table 2 shows that you need nozzles that will deliver
22.4 ounces or 0.175 gallon ])er minute. Use a nozzle
manufacturer's chart to select a nozzle having this flow
rate at a pressure of a])i)roximately 25 pounds per
square inch.

After selecting the proper nozzles and mounting
them on the planter or sprayer, you should check the
flow rate of each nozzle. Table 2 can be used for this.
With water in the tank of the sprayer, start the i)umi)

Table 2. — Nozzle Flow Rates Require(

Broadcast

Gni

rate

3 4

gal. gal. oz. gal. oz.

per per per per per

acre min. min. min. min.

10 .065 8.4 .087 11.2

15 .098 12.6 .132 16.8

20 .131 16.8 .175 22.4

25 .164 21.0 .218 28.0

30 .196 25.2 .262 33.6

and adjust the pressure to the value for which the
nozzles were selected. Collect the spray in a jar or
cup marked for ounces. Use a stopwatch or a watch
with a sweep second-hand to check the time. Adjust the
pressure until you collect the correct number of ounces
per minute from a nozzle and then check all of the
other nozzles. If a nozzle fails to give the proper flow
rate or if its flow rate is significantly different from the
others, check to see if it is clogged or damaged and
replace it if necessary.

You are now ready to mix the chemical in the spray
tank and start spraying. Make sure you spray at the
speed and pressure you selected earlier. Table 1 will
help you to determine how much you should use per
crop acre and per field. After spraying an acre, and also
at regular intervals, you should check the amount actu-
ally being applied with that recommended. In the exam-
ple given, to apply the equivalent of 20 gallons broad-
cast per acre, a 13-inch band on 30-inch rows would
require 8.7 gallons per total crop acre; on 36-inch rows,
7.2 gallons; and on 40-inch rows, 6.5 gallons.

Band width

Obtain the band width of 12 to 14 inches by chang-
ing nozzle height.

Start with the nozzles 8 to 10 inches above the
ground, but make the final adjustment for the band
width in the field with the planter in planting position.
Turn the sprayer on for a few seconds ; then shut it off
and measure the width of the wetted strip. Check the
band width after the pressure has been set, because
the spray angle of the nozzle is affected by pressure.

fir 13-Inch Band Regardless of Row Spacing
'' il speed (mil es per hour)

^al.

oz.

per

per

mm.

mtn.

.109

14.0

.164

21.0

.218

28.0

.273

35 . 0

.328

42.0

gal.

oz.

per

per

mm.

mm.

.131

16.8

.196

25.2

.262

33.6

.328

42.0

.393

50.4

gal.

oz.

per

per

mm.

mm.

.153

19.6

.229

29 A

.306

39.2

.382

49.0

.458

58.8

Trouble shooting

If the flow rate of the spray pattern i.-^ faulty or
irregular, the nozzle tip or screen may be plugged or
damaged. Use an air hose to blow out particles or clean
the tip or screen with a toothpick or toothbrush.
Never use a hard object. Do not touch the Jiozzle to

Sprayed band should extend beyond the
press-wheel ridges. (Fig. 2)

Table 1. — Amount of Spray Solution to Band Spray
One Acre (With a 13-inch Band)

Broadcast

Row width (inches)

rate

30

36 38 40

gal. per

acre

gal.

per acre for hand spraying

10

4.3

3.6 3.4 3.2

15

6.5

5.4 5.1 4.9

20

8.7

7.2 6.8 6.5

25

10.8

9.0 8.5 8.1

30

13.0

10.8 10.3 9.8

Example: If you apply a spray for which the rec-
ommended broadcast rate is 20 gallons per acre in a 13-
inch band on 36-inch rows, you will actually use
13/36 X 20, or 7.2 gallons per crop acre.

Table 1 can also be used to determine the amount of
solution used per crop acre.

Cfieck ground speed carefully

Since speed affects the amount of chemical that is
applied, it should be checked carefully in the field
where the chemicals will be used. Each check should be
made with a running start. One method is to set two
markers 176 feet apart and check the time (in seconds)
required to drive between them. To determine the
speed in miles per hour, divide 120 by the travelling
time in seconds. Some examples are given below.

Time required
to drive 176 feet Speed

(seconds) (miles per hour)

40 3

30 4

24 5

20 6

17 7

Once you have established and checked the field
speed, keep the speed uniform during application. You
may want to mark the speed indicator dial or the gear
and throtde setting. Keep the throttle at the same
setting when checking the nozzles as when actually
spraying. Tractor speed indicators can be in error be-
cause of changes in tire size and wheel sHppage so do
not rely on them without checking.

SUPPLY TANKS

PRESSURE
REGULATOR

PRESSURE
GAGE

Diagram of band-spray attachment. (Fig. 1)

Preemergence herbicides need to be applied as ac-
curately as possible to provide good weed control and
to avoid injury to present or future crops. Read the
container label carefully to be sure that you know how
much herbicide to use. Unless specified otherivise, the
recommended rates are for broadcast application.

Because in band spraying you are covering only a
portion of the field, the actual amount of solution you
will use per crop acre is less than the broadcast rate.
But the amount applied to that portion of the soil that
is actually treated is the same for both banding and
broadcasting. The amount you will use is:

width of band (inches)
row spacing (inches)

X

broadcast rate
(gallons per acre)

the mouth and be sure to discard toothpicks or tooth
brushes immediately after use in such a way that chil-
dren or pets will not pick them up.

Nozzle-clogging problems are often the result oi
improper mixing, insufficient agitation, a dirty tank oi
lines, dirty water, or improper screen sizes.

If drift is excessive, reduce the pressure or usf
wind guards. Larger nozzles may be necessary to gei
pressure well below 40 pounds per square inch.

If the pressure regulator will not adjust to a low
enough pressure, it may be stuck or the bypass hose
may not be large enough.

Caufion

Some preemergence chemicals are irritating to the
skin. Heed the warnings on the containers and use
rubber gloves and goggles when and where recom-
mended. Avoid breathing mists, vapors, or dusts dur-
ing mixing and application.

Additional information

If you want additional information on the applica-
tion of herbicides, you may obtain single copies of the
following publications from the Office of Publications,
123 Mum ford Hall, University of Illinois, Urbana,
Illinois 61801, or from your county extension adviser. ^
Calibrating and Maintaining Spray Equipment. Cir-,
cular 1038.

Calibrating and Adjusting Granidar Row Applicators.
Circular 1008.

Prepared by J. C. SIEMENS, Associate Professor of Agricultural Engi-
neering, and B. J. BUTLER, Professor of Agricultural Engineering. This
circular replaces Circular 791 of the same title.

Urbane, Illinois December, 1971

Issued in furtherance of Cooperative Extension Work, Acts of May 8
and June 30, 1914, in cooperation with the U.S. Department of Agri-
culture. JOHN B. CLAAR, Director, Cooperative Extension Service,
University of Illinois at Urbana-Champaign.

8M— 12-71— 19917

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SvERSlTYOFlUlNUlS-UMANA

10471971