Fig. 122

wheeled tractor shown towing the mower.

A somewhat more elabo-
rate rotary mower is the
one shownin Figure 122
and used on the Rio Grande
Projectin Texas. Pulled
by a wheeledtractor,

the commercial mower
is used to good advan-
tage inclearing wider
areas at one pass.

The outer sections of

the mower are hinged
andcanbe raisedor
loweredhydraulically.
Power for operation

of the mower is fur-
nished by the diesel-

Inaneffort

to reduce
costs and more
efficiently con-
trol the algae
andweeds,
both in the
canals and
drains, as
well as onthe
banks and side
slopes, the
heavy-duty
weedand brush
cutter shownin
Figures 123,
124, 125, and
126has been
usedin recent
years.

The machine
consists princi-

pally of large drums equipped with heavy-duty, double-edged reversible
blades, with drum and blade assembly carriedina heavy-duty towing
frame. The machine is versatile, as illustrated, and units can be used
side by side or intandem, andcan be set with or without angle, depending

onthe work to be done.
weight is desired.

The drums can be filled with water if additional

When the cutter is used to remove algae or aquatic weeds, as shownin
Figure 124, itis set up tandem and offset so that when pulled forward it


PI63-p-29245

Fig. 115

Accordingly, this limited the burned area to only part of the
canal and drain slopes. To complete the job, it was necessary
to use laborers and hand burners to extend the burning to the
bottom of the canals, to the water surface in the drains, and to
the tumble weeds generally located near the water's edge.

The project was well equipped with chemical spray equipment,
which included a 33-foot hydraulically operated sectional spray
boom. This boom was utilized with an adapter to spray a burner
oil or a like material and accomplish the job more effectively
and economically. Figure 115 is a view of the unit in operation.

The spray equipment, all mounted on a 1-ton, four-wheel drive
truck, consists of a turbine pump, direct connected to a gasoline
engine. A 4-foot extension was added to the end of the spray
boom, and with a tee and two sections of pipe, provided for the
mounting of three 6502 tee jets at 20-inch spacings. The tee
jets were drilled out to enlarge the holes and make it possible

to apply approximately 100 gallons per hour of diesel oil in small
droplets at an approximate pressure of 25 pounds per square inch.
The more detailed view of the burner in operation, Figure 116,
shows the 4-foot extension, burner tip, and bracing of the burner
tee to the extension pipe.

With the 33-foot boom and extension, and pumping facilities on

the spray truck, it is now possible to completely cover the entire
perimeter of the drains and large canals with a minimum of effort.

101


disks, or to control the direction of the disks. The disks also can be
raised over drops or other obstructions by manipulating the cables and

boom,


and steep slopes are the same problems encountered in spraying.
Access to the rights-of-way are even more important than in spray-
ing. Retention of heat on the weeds is difficult. Covers like those
used in flame cultivation are usually too cumbersome for irrigation
system burners.

Equipment Types

Liquified petroleum gases (L. P. gases) such as butane, propane,
and mixtures of the two, are supplied under pressure in tanks.
Pressures up to 200 pounds per square inch are involved. Regu-
lators are provided to supply the fuels in the gaseous or liquid
form at a pressure suitable for the particular type of burner. No
pumps are required. Pilot lights may be readily attached for
remote ignition of the burners.

Fuel oils do not require pressurized tanks, but do require pressure,
as from a pump. Certain burners are preheated to burn the oil in
its gaseous form. Others burn with an oily residue which may have
a toxic effect on plants. Still other fuel oil burners.depend on atom-
ization or spraying of the oil in a fine mist prior to ignition. A
recent adaptation of this method incorporates a blower to add air

to the atomized and ignited oil.

Liquid Gas Weed Burners

In the past few years, an effective burning program for weed con-
trol has been put in operation by Region 5 of the Bureau of Recla-
mation, on six projects in New Mexico and Texas. This was
brought about by the introduction and availability of liquid gas,
particularly butane and propane. Although other methods of grass
control in distribution systems are effective, burning still has a
place in the routine weed control program. This is more appli-
cable since liquid gas burners, mounted on both trucks and trac-
tors, have been developed.

Several important and beneficial features have been incorporated
into the burners used in Region 5, shown and described on the
following pages. These features include:

1. Vaporization of liquid at the burner;

2. Swinging of booms so that the truck may traverse either
bank of a canal; and

3. Cables or hydraulic means to raise and lower the burners
so that they can be kept in the most effective burning position.

92


has a vigorous action and

the cutting edges on the two
units overlap each other,
cutting the growth into
lengths of approximately
12inches. The vigorous
action of the cutting edges
inthe tandem offset style
tears the growth loose and

in many instances uproots
the aquatic weeds. White
roots are often seen floating
inthe lateral after the machine
passes. After the growthis
torn loose, itcanbe floated
out with the irrigation water.

Whenthe cutter is set up
with the drums side by side,
Figure 125, the unit canbe
used with one drum running
on top of the bank andthe
other drum onthe slope,
either on the inside or the
back side of the canal.

The cutter canalso be used
ona cable behinda tractor
toclean along drainage bank
slope, andwhenclosely
hitched to the drawbar ofa
tractor, thecutterisan
excellent piece of equipment
toclear wide flood channels
ofundergrowth. In this man-
ner, the machine canalso be
usedtoclear land prepara-
tory to land leveling.

A single D-8 tractor has
been used to pull the 7-foot
long cutter on much of the
work. Inclearinga lateral
choked witha growth of
algae and aquatic weeds,
Figure 124, the tandem
cutter was towed by two
largetractors. Opera-
tions ona side slope with
the cutters intandemis
shown in Figure 126.


The cutter is reported to work very effectively in gravelled substation
yards where the cutter bar is set to cut 2 or 3 inches below the surface.
In moving forward the blade slides through the gravel cutting the weeds
below the surface and bulking and freshening the packed gravel. In back-
ing, the blade drags, pulling out the weeds and leveling the gravel.

The cutter was built at a cost of $22.95, all of which was labor. Mate-
rials for construction of the device were obtained from the shop scrap
pile. It is estimated that work previously accomplished by two men in
40 hours, is now done with the cutter in about 5 hours.

Disks, Drags, and Similar Equipment

Many of the pieces of equipment used in the control of growing weeds
also are applicable to or a part of the disposal of weeds and are dis-
cussed in the section of this bulletin devoted to this subject; however,
one device, Figure 129, is typical of the devices of this type that can be
used for cutting water weeds growing in channels, in that many of them
must be operated in an "off-set'' position behind a towing device.

Operated by the Truckee-Carson Irrigation District, Newlands Project,
Nevada, the unit has been very successful in controlling water weeds in
large canals,

A boom is mounted on the back of a tractor. Two rows of heavy disks,
18 inches in diameter, are attached in tandem to the boom by adjustable
cables. The cables are controlled from the power takeoff and can be
adjusted to lengthen or shorten the distance between the boom and the

MISS JJJJI

ROAD
—_—— WIJ)
1“ Ban apes o ani =z = 7
\, oa
wa CANAL
/ a
na
elt +
Fig. 129

110



Fig. 119

Fig. 120

On the Donna Division of the Lower Rio Grande Rehabilitation
Project, Texas, Figure 120, a commercially available 60-inch
offset shredder mounted behind a small diesel tractor is shown

105


Fig. 109

A general view of another butane trailer-mounted weed burner
in operation on the Fort Sumner Project, New Mexico is shown
in Figure 109. Note the air turbine mounted to blow the flame
out the stack.

Burners constructed on trucks, half-tracks, or trailers, burn

to the side and behind the carrier, while those that are tractor
mounted, burn to the side and in front of the transporting vehicle.
The latter are used in Region 5 entirely for searing and burning
green weeds and grasses.

A project shop-constructed, tractor-mounted liquid gas weed
burner used on the Tucumcari Project, New Mexico, shown in
Figure 110, consumes about 70 gallons of liquid gas per hour
under continuous operation. The machine operates at about

2 miles per hour when burning green weeds.

Intense heat from the burning of dry weeds in front of the tractor
and butane tank makes this machine impractical for winter cleanup.
The boom of the burner on this rig is raised and lowered hydrauli-
cally and rotated with a mechanical screw device.

Another tractor-mounted liquid gas weed burner is that shown in
Figure 111. This burner is used on the Fort Sumner Project,
also in New Mexico. This burner also was constructed by project
personnel in the project shops. It is hydraulically operated.

In operation on a project lateral, the burner head works to the
side and front of the tractor, which makes it easily visible to
the tractor operator. Like the previous tractor-mounted burner
used on the Tucumcari Project, care is used in burning because
of the proximity of the tractor and the butane tank.

97


Fig. 104

lateral are being burned by the truck mounted burner constructed
in the shops of the Carlsbad Project, New Mexico, by project
personnel. In this type of burning, the truck travels about

3 miles per hour.



Vaporization of the liquid at the burners eliminates special heat
exchangers which are dangerous, expensive, and burdensome.
Many of the burners used on the equipment described were
designed and fabricated on the several projects by project per-
sonnel, They may be mounted in clusters on the burner bars.
The bars, usually, are mounted on black standard pipe which in
turn telescopes over smaller pipe attached to the boom. The
bars can be moved away from or pulled closer to the truck and
can be raised or lowered hydraulically or by the use of cables,
pulleys, and cranks, generally by one man.

The burner heads for many of the burners were constructed of

old boiler flues; however, the most durable are constructed of
seamless steel tubing. A heat generating burner head is desirable
and probably the most efficient, however, is not a necessity, as
liquid gas will burn without producing much smoke, even when
released through an open jet nozzle.

With a swinging boom, the truck can move on either bank of the
canal while burning, the burners can be swung to the rear of the
truck when burning the top of the canal bank, or the boom can be
swung to a forward position when moving from one location to
another. Burning weeds in a canal with an operating road on
only one side is made more convenient and effective and wind
conditions can be tolerated, by proper manipulation of the boom.

In order to burn canals having variable distances from the road-
bed to the waterline, most of the burners shown have easily
adjustable burner bars, which can be controlled from the
operator's seat and can be maintained in the proper burning posi-
tion at all times.

The butane weed burner shown in Figure 104 is a little more
elaborate than the usual burner of this type in use. The weed
burner shown was constructed and is owned and operated by a
custom-burning contractor in El Paso, Texas. The owner con-
tracts to burn weeds from ditches on a portion of the Bureau of
Reclamation constructed Rio Grande Project. This arrangement
has been in effect since 1949. The cost of burning with this and
similar rigs in 1956 averaged about $17.00 per mile for one canal
bank and $26.00 per mile where both banks have been burned.

There are differences in the design and construction of booms
and mountings, which reflect the ideas of the several builders.
The booms may be either manually or hydraulically controlled
and are in general 25 to 30 feet in length. There are usually
counterbalanced for ease of manipulation. The manually con-
trolled boom, such as that shown in Figure 105, is mounted ona
turntable, which permits operations from one side of the truck to
the other from the rear of the truck bed. The weeds ina small

93


in use mowing an embankment along a project canal. The shred-
der can be utilized to mow either up or down on side slopes.

Fig. 121

An unusually wet month of July caused a very heavy growth of
weeds on the canal and lateral rights-of-way of the Tucumcari
Project in New Mexico, as well as in the water prisms, since
the ditches were empty much of the month. In order to use
mower tractors and operators in the most efficient manner, a
7-foot sickle cutter bar was placed on the side of one tractor
already equipped with a three-rotor, 8-foot cut, rotary mower
mounted on the rear. This made it possible for the one machine
to cut a 15-foot swath, clearing the operating road and one bank
of a lateral in a single operation, as shown in Figure 121.

The side-mounted sickle cutter bar is driven by a hydraulic motor
while the rotary mower is driven from the tractor power takeoff.

The machine operated very smoothly and covered a lot of ditch-
bank ina short time. The project is so well pleased with the
operation of this machine that a second one has been purchased.
Both the rotary mower and the hydraulically-driven sickle mower
are available commercially. The price of the hydraulic mower is
about $900.

106


P23-509-3036
Fig. 107

Figure 107 illustrates the use of a burner mounted on a 2-ton
truck equipped with a 30-foot swinging boom with a series of
burners attached. The boom is regulated by a cable-control
system, and the burners use a propane-butane mixture. This
and three other similar burners are used on Las Cruces Branch
of the Rio Grande Project, Texas-New Mexico.

Fig. 108

Burners mounted on trailers are shown in Figures 108 and
109. Figure 108 is a view of a trailer-mounted liquid gas weed
burner in operation on small lateral on the Balmorhea Project,
Texas. A third burning of the year is in progress.

96


Portable Mist Sprayer

A motor-driven mist sprayer adapted for local application of insecti-

88

cides such as for mos-
quito control is shown
in Figure 99. Use of
equipment of this type
may replace handwork
in areas inaccessible
to wheeled or track
type vehicles, and on
sites so located that
drift of a highly con-
centrated herbicide

on to adjacent crops
or other valuable
plants is not a factor.

Hand Spray Shield

The light-weight
shield for use ona
hand-boom when
spraying various
weed control mate-
rials shown in.Fig-
ures 100 and 101,
was fabricated by
project forces on
the Central Valley
Project, California.

The shield reduces
the drift of weed
control materials

by excluding the

wind from part of

the spray fan. It

is particularly
adapted for use in
spraying weed oils
under overhanging
branches of shrubs
and trees. The
shield effectively
prevents the branches
from being sprayed by
the drifting weed con-
trol material.


when the green plants reach a height of 8 to 10 inches, weedy
grasses and undesirable vegetation on the inside slopes of ditches
have been successfully controlled.

A weed burning program has been employed on a part of the

Rio Grande Project, Texas-New Mexico, for several years. In

1949 and 1950 five to six burnings were necessary to keep the
Johnson grass suppressed to the extent it did not retard the flow

of the water in the canals and laterals. Following the same proce-
dure for Johnson grass control during the years, only four burnings
were necessary in 1954, and it was indicated that only three burnings
would be required in 1955.

In 1954, the average cost for burning green weeds onthe inside of
small ditches onthe Carlsbad Project, averaged $8.78 per mile per
burning, and the cost of burning 35 miles of small ditches on the
Balmorhea Project, Texas, averaged $7.80 per mile of burning.

Oil Type Weed Burners

Several projects are now using fuel oilinthe burning of weeds. One
such machine usedonthe Middle Rio Grande Projectis shown in Fig-
ure 112, The boom onthe burner is 20 feetinlength, and the burner
uses about 150 gallons of fueloil during an 8-hour work period.



Fig. 111

Cost of burning varies from project to project and depends on the
amount of liquid gas consumed per hour of operation and the num-
ber of burnings required to suppress the vegetation. Ordinarily,
liquid gas weed burners operated on a tank pressure of about

100 pounds per square inch, and each burner head will consume

8 to 12 gallons of liquid gas per hour. The efficiency of liquid gas
burners is considered very high as little smoke is evident.

On ditches heavily infested with weeds and grasses, two burnings
are ordinarily recommended. The first burning being accomplished
with the equipment moving at a rate of about 3 mph. This searing
results in an effective top kill even though there is little immediate
change in plant appearance. The second burning, made about a
week to 10 days later, consumes the old dead tops and retards any
regrowth of new plants. By continuously burning and reburning

98


Fig. 106

Another burner that is very universal in operation, easily adjust-
able to meet unusual conditions, andvery mobile, is that shown in
Figure 106. This rig was constructed by project personnel in the
shops of the Tucumcari Project, New Mexico. It is hydraulically
operated, and hydraulic mechanism from an old pull grader was
used for the controls on this machine. The operator sitting on the
truck bed turns with the boom, which also is controlled hydrauli-
cally in its horizontal and vertical movement.

The burner consumes about 70 gallons of liquid propane fuel per
hour under continuous operation. The truck ordinarily travels

1 to 3 miles per hour in burning green weeds and grasses, the

rate of travel varying with the height of the canopy and the smooth-
ness of the road. In burning dry weeds, the rig travels 5to6 miles
per hour.

A 400-gallon tank has been mounted across the truck frame and the
liquid butane is piped from the tank to the burners. A high-pressure
regulator set at 50 pounds pressure is used to control the flow of
butane to the burners.

The swinging boom is made of pipe and is mounted on a mast pipe.
The mast pipe consists of two pieces of pipe, actually, with the
smaller top pipe mast fitting inside the larger lower pipe. Roller
bearings at the top and bottom of the mast pipe provide for easy
movement. A support made also of pipe and mounted on the front
bumper of the truck is provided for the boom to rest upon when
traveling from one location to another, or when the rig is not in
use.

95


A simple weed cutter which can be used very effectively in substation
yards to reduce maintenance costs has been constructed by the power
O&M crews of the South Platte River District, Region 7. The device
was constructed for attachment to the front bumper of the truck as
shown in Figures 127 and 128.

Fig. 127

Power winch and
cable reel~.

37Angle iron clips
bolted to bumper

Power wagon bumper--~

“-Set screw for adjusting

-----2" Pipe with i$" pipe dapth: oF Gut

inside for reinforcement

5 Ft. long used grader

poe" 4" Bolt with cotter pin
blade, sharpened-._

I$ Pipe--

: , s--1f! Pipe
£ Bolt welded to 1° pipe----- a z

~2"x2"x tT Angle iron
Angle clips bolt to

existing holes
in bumper --

2"xt Strap iron
Malle GT Weld

Pipe 10" long

POWER-WAGON MOUNTED WEED CUTTER

Fig. 128

109


In this way one strip sprayed with the logarithmic sprayer will take
the place of a large number of dosage plots. Such a trial plot is
shown in Figure 103 of a roadside weed control test area in Yolo
County, California.

Further information on the principles of design and construction of
this sprayer may be obtained by addressing the Regional Director,
Region 2, Bureau of Reclamation, Sacramento, California.

Burning Equipment for Control of Land Weeds

Weed burning may be divided into two phases: (1) that of control
which involves the burning of green weeds during the growing sea-
son, and (2) that of disposal which involves the burning of dry
weeds, before and after the irrigation season, or at any time of

the year. Because the heaviest use of burning equipment is in those
areas of green weed control, the burning of dry weeds will be treated
in the third section of this release, as a weed disposal practice.

Weed burning is a major weed control practice in those geographic
areas which have one or more of the following problems:

1. Non-weedy grasses are difficult to establish, as competition
to weeds.

2. Effective herbicides are not available, are too expensive, or
are prohibited because of hazard to crops.

3. The combined economic and physical factors favor burning
over the cost of change to non-weedy vegetation.

The Problem

Weed burning requires fuel, manpower, and somewhat specialized
equipment. Burning usually requires more travel over the rights-
of-way than spraying of the hormone-like herbicides. Where burn-
ing is feasible, equipment, fuel, and manpower must be available
at a reasonable cost.

Irrigation season burning which may cause ground fires on dry
rangeland in some areas, would not be a limiting factor on a fully
developed irrigation project which surrounds the canals and laterals.
The most important problem is in the design of mechanical devices
suitable for putting the flame where the weeds are. Long reaches

91



Fig. 116

While the use of oil as a catalyst for burning debris and willows

is no innovation, this burner constructed by the Middle Rio Grande
Project forces is accomplishing a far better job than formerly
accomplished by the use of a propane burner. The modified

burner has improved the efficiency of the operation by 20 to 30 per-
cent, and, although the greatest improvement has been on the’ drains
and larger canals, some further savings are being realized by being
able to burn the entire section of smaller canals.

A combination trailer-mounted weed sprayer and burner was
designed and constructed by personnel of the Lower Colorado River
Indian Agency, Parker, Arizona, Figure 117. Units of the size and



Mowers

Wheel-type farm tractors with hydraulic and mechanical con-
trol of conventional cutter bars are used on many projects in
maintaining canals and laterals. Heavy-duty equipment of simi-
lar type is also available commercially. One such commercially
available mower is shown in Figure 118. The mower is com-
pletely hydraulically operated. The cutter bar is extendable and
retractable. Contractors clearing drains for rehabilitation on
the Middle Rio Grande Project, New Mexico, used the mower
with various degrees of success. The cutting of phreatophyte
fringe growths along canals and drains requires a machine that
is much more durable than for grass cutting. The cutter is
designed to mow plants up to 3 inches in diameter.

The Middle Rio Grande Project has acquired a machine of the
above design and mounted it on a crawler-type tractor, Fig-
ure 119. With the cutter bar in the partially raised position as
shown, obstacles and structures can be easily cleared.

104


Fig.



t

oa
ZZ + 9
je NOZZLE i

|

. mS ie

/ fe \ if f
/ ‘ who?
TM. SPRAY FRN --7 IZ |
y . | !

\

S—— SHIELD~ made ef \ { |

| 46" sheet aluminum ; |

I} os

— iL

| SIDE VIEW END

Special Sprayers

A great deal of testing of herbicides on land weeds is done by the
State Universities, the State Agricultural Extension Service, or
Branches of the U. S. Department of Agriculture. Where these
data are not available, or do not apply it may be necessary for
irrigation projects to participate in trials which reflect the local
weed, soil, and climatic conditions.

No chemical formulation is likely to kill a given weed with a given
formulation and dosage under all environments. Best use of the
chemical demands that knowledge be obtained from local trials.

Where such trials can be made by local representatives of the
agricultural agencies, or in cooperation with them, the log-
arithmic sprayer, Figure 102, is useful and saves time in appli-
cation and evaluation of trials.

First, all the dosages (amount of chemical per acre) may be
applied in one continuous swath. Second, the exact dosage for a
given section of the plot can be calculated by measuring from one
end of the swath. Third, the subdivision of dosage is infinite. For
example, 2,4-D may be applied at a dosage range of 1 ounce to

40 pounds per acre in mixed vegetation. Results may range from
no damage to complete kill of all the vegetation, including various
points of selective control. The dosage can be calculated at any of
these points.

89



Burning of weeds ona
California Project using
a commercially available
burner mvuunted in the
back of a 1-1/2 1 flat-
bed truck is shown in
Figure 113. Note the
spray rig at right center
of illustration. Proj-
ects on which there is
dry native vegetation
beside the canal right-
of-way must maintain
adequate fire control
apparatus to prevent

the spread of fire to
adjacent lands.

P2i4-D-29247

Fig. 113 A somewhat similar

but smaller burner is
that shown in Figure 114
used by the Kennewick
Irrigation District on
the Yakima Project,
Washington.

There are approximately
350 miles of large river-
side and interior drains
and 200 miles of rela-
tively large main canals
on the Middle Rio Grande
Project in New Mexico.
As arule, these water-

L “+ gp :
P33-D-29246 ~ — 5 eee ways and drains are
—— ~ — 8 to 12 feet in depthwith
Fig. 114 comparatively long side

slopes. Willows, salt
cedar and other native vegetation grow profusely on these side slopes.

The weed control procedure in the past had included chemical spray-
ing of this vegetative area using a 33-foot hydraulically operated
spray boom. After the brush had been killed or controlled, the next
step consisted of mowing with a heavy duty mower leaving the tops of
the dead vegetation and other debris in place until it had dried suffi-
ciently and could be burned. Burning of the vegetation and tumble
weeds that accumulate throughout the perimeter of the drains and
waterways was accomplished largely by the use of propane-butane
burners mounted on trailers pulled behind trucks or tractors.

Unfortunately, the length of the boom used was limited to about 10 to
15 feet of area; the radius of the boom from the edge of the trailer.

100


design shown have proved very useful for spraying or burning
undesirable weed growths on farm ditches, along fence lines,
and other places. Similar light compact machines can be used
advantageously on irrigation projects which have narrow and
inaccessible ditchbank operating roads.

The tank, engine and pump combination, and boom pedestal
can be constructed as one unit on a frame which is detachable
from the trailer. A positive means of agitation has been
included in later models of this machine. A sprayer with
an agitator is required for successful application of oil-water
mixes, emulsions, suspensions, and for proper stirring of
most herbicides or insecticides with the diluent being used.

A small gasoline engine was used to drive the pump on the unit
pictured, but other models have the pump attached to the tractor
power takeoff shaft.

A gear, piston, or centrifugal pump which develops from 40 to
90 pounds pressure per square inch is satisfactory for spraying,
but for burning, higher pressures are preferred. A pressure
regulator and pressure unloader should be installed with the
pump so discharge to the nozzles is constant and unvarying.

Thé boom is constructed of double strength steel tubing rein-
forced with struts and turnbuckles. Oil resistant hose and high
pressure fittings are used on the pictured machine. The boom
pedestal can be moved to either side of the trailer which allows
the operator to direct the boom into the ditch.

Mechanical Equipment For The Control Of Land Weeds

Various types of mechanical equipment have been used in the
control of land weeds. Some equipment is relatively simple
and inexpensive and other equipment is expensive and costly.
Some newer machines such as mowers and shredders are now
on the market and many of these accomplish a great deal of
work in a short while.

Until very recently, farm-type equipment fulfilled the needs

on most projects, although in some instances inefficiently.
Mowers, brush cutters, drags, disks, and other special

pieces of equipment to accomplish a particular job are included
in the list of mechanical equipment used by various organizations
and agencies in the control of land weeds. New equipment now
available commercially has contributed to increase efficiency
and made it possible to do work previously only accomplished at
very high cost, if at all.

103