The Rural Voice, 1985-11, Page 32vim
MERVYN ERB
The nozzle makes the difference
Last March while attending a week-
long course at Michigan State Univer-
sity, I and the others in attendance
spent an entire day in the Engineering
Department's workshop. The day
was filled with films on spray applica-
tions, nozzle performance, infrared
photography of distribution of spray
material in soil, and hands-on work
with nozzle settings and spray pans.
One of the most interesting nozzle
tips we worked with was the new twin
orifice flat fan tip from Spraying
Systems. As the name implies, this tip
has two slots cut into it. One faces
forward at a 45° angle and the other
faces backward at a 45° angle. The
idea behind this is to obtain move-
ment of the crop and weed canopy
when doing post -emergent spraying,
so as to "flop" the vegetation back
and forth.
You're probably using the right
pesticide in the right amount, but are
you using the right nozzle? Using the
correct nozzle for foliar work can
make the difference between excellent
and poor results, especially with low-
volume applications.
Spray coverage and canopy
penetration determine the effec-
tiveness of many foliar pesticides
(herbicides and insecticides). Spray
Mervyn Erb,
a regular
contributor
to the Rural
Voice, is
crop
specialist at
the Hensall
District
Co-op
coverage refers to the number of
droplets per unit area. The most im-
portant variable determining
coverage is droplet size. For a given
application volume, smaller and more
uniform droplets result in more
droplets per square inch.
Canopy penetration is the degree at
which spray droplets penetrate the
canopy and make an impact on the
foliage. Variables which include
droplet size, air velocity, canopy den-
sity, and nozzle orientation affect the
ability of pesticide droplets to
penetrate the plant canopy.
Laboratory techniques are
available to measure both spray
coverage and canopy penetration.
S.L. Pearson and L.E. Bode
presented a study at Urbana, Illinois
last January in which they reported
results of a field test conducted to
compare lab results with actual spray-
ing conditions. Seven nozzles were
tested.
Weed control was evaluated in an
area infested with both grass and
broadleaf weeds, specifically oats,
foxtail, and velvetleaf. Gramoxone at
1 1/2 litres per acre was applied with
each of the seven nozzles being com-
pared.
The most consistent control of
both types of weeds resulted from ap-
plications with the twin orifice flat
fan nozzle. The use of this nozzle
resulted in 95 per cent weed control at
application rates of both 10 and 20
gallons per acre.
Nearly as effective as the twin
orifice nozzle was the regular flat fan
nozzle. The use of this nozzle resulted
in weed control as high as 90 per cent.
The twin orifice and the regular flat
fan nozzle were on 20 -inch spaces.
Both were operated at 40 psi at the
nozzle.
The Micromax rotary nozzle at a 2
gallons/acre rate gave good control
of the oats and foxtail — 85 to 90 per
cent — and fair control of the
velvetleaf — 50 to 65 per cent. Little
difference in control was noted bet-
ween 2,000 and 3,500 rpm disc
speeds.
The two flood jet nozzles, TK 1.5
and TK 2, also gave good control of
the oats and foxtail — 70 to 85 per
cent — and fair control of the
velvetleaf — 50 to 75 per cent. The
TK 1.5 flooding nozzles were
mounted at 30 -inch centres. The TK 2
flooding nozzles were mounted at
40 -inch centres. Both were operated
at 40 psi pressure.
The Deere and Company elec-
trostatic nozzle performed poorly in
control of both the grass and
broadleaf weeds. Non-uniform
distribution patterns resulted in weed
streaking from the electrostatic unit.
Weed control of 5 to 10 per cent was
noted.
The Spraying Systems air assist
nozzle also performed poorly in con-
trol of both types of weeds. The air -
assist nozzle uses liquid pressure to
meter the chemical to the nozzle and
additional air pressure to break up
the spray and form the nozzle spray
pattern. It is an experimental nozzle
and performance should improve
with adjustments in the air and liquid
pressure.
The study demonstrates that using
the same pesticide, Gramoxone, on
the same weeds (oats, foxtail, and
velvetleaf), can result in strikingly
different results. Pearson and Bode
noted a range of weed control from a
high of 95 per cent to a low of zero.
In every case, the nozzle made the dif-
ference. ❑