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IV. Developments in Cultivating Equipment
RECENT DEVELOPMENTS IN AGRICULTURAL MACHINERY
3/16 inch thick, they are self-sharpening and can be used without other
care until worn out.
Hydraulic controls have replaced nearly all of the mechanical lift
equipment. Double-acting cylinders permit positive penetration under
hard-ground conditions. In some instances the units on each side of the
tractor can be lifted or lowered independently. This provides a great
advantage when cultivating along grass waterways, variable-width contour strips, and terraces. In tractors equipped with both front- and rearmounted units, delayed-action valves are being used to permit the rear
gang to stay in the soil until they have moved forward to the field edge,
where the front gang was raised.
There have been many modifications in plant-shield design. Rotary
shields and floating self-adjusting stationary shields permit much closer
operation to the row. To improve this further, one company has developed an electronic control mechanism that automatically senses the
position of the cultivator in relation to the plant and then transmits this
to an automatic power-steering mechanism. This system virtually eliminates the hazards of human error in guiding the tractor in close-cultivation work.
The rotary hoe, and a number of its modifications, has been in use
for many years, Recent improvements in design and construction has
placed new emphasis upon its use. A major design change has been the
sectional and individual suspension of the spiders in place of the single,
rigid axle mounting. This has resulted in maximum flexibility, allowing
the unit to conform to surface irregularities, and thus doing away with
the problem of excessive depth of penetration on high spots and weeds
left in depressions. Rea (1954) has shown that excellent results can be
obtained with such equipment at speeds up to 18 miles per hour. R. W.
Wilson (1956b) has also shown that this equipment has considerable
promise in early cultivation of tobacco.
Sectional units consisting of three or four rotary-hoe wheels have
been mounted on conventional planters directly over the crop row in
order to break crusts and dislodge small weeds that could not be reached
with conventional cultivating attachments. Rotary cultivating units, in
which the row middles are stirred by units driven from the power takeoff that have various-shaped knives and blades mounted parallel to the
axis of rotation, have been developed for cultivating special crops. The
degree of soil pulverization can be controlled by adjusting the relative
speed of rotation to the rate of forward travel.
There is continued effort to find better ways of controlling weed
growth in the row where it is difficult to reach without injuring the crop.
T. W. EDMINSTER AND H. F. MILLER, JR.
Liljedahl et n2. (1956) proposes the use of heat, ultrasonic and impact
energy to damage weed seeds in the soil before planting. They developed experimental equipment for picking up the soil in the immediate
area in which the seeds are to be planted, treating it, and then replacing
it immediately in front of the planter. Initial results indicate that such
an approach should be given thorough study, particularly where special
high-value crops are to be seeded.
Flame control of weeds on ditch banks and rights-of-way has become a standard practice. Its application to weed control between plants
under cultivation was first considered in the early 1940’s.
Major attention has been given to the use of flame cultivators in
cotton growing. Stanton ( 1954) and Stanton and Tavernetti (1956) have
outlined in detail the development of more precise and uniform seedbeds, This, together with uniform seed depth, results in a plant uniformity that permits close adjustment of the flame with minimum plant
damage. Several burner designs involving various shapes, slopes, and
types of flame deflectors have been developed. Staggered mounting prevents the flames from striking each other and thus being deflected up
the plant. In some areas, particularly California, there is growing interest
in this equipment.
Weed control specialists have made tremendous strides in the development of chemicals for the control of weeds in cultivated crops.
Equipment for the application of these chemicals has passed through
many stages of development. Basically, it consists of standard assemblies of tanks, pumps, pressure-control regulators, and application nozzles. Engineers have been challenged to develop units that can be used
in conjunction with planting and mechanical cultivation equipment.
Nozzle designs that will give a uniform, precisely placed application
with a minimum gallonage have been the major objective.
Most of this equipment is rather standard in design and application,
and hence will not be discussed in detail. Excellent discussions of its
development, design, and use are to be found in the reports of Akesson
and Harvey (1948), Fairbanks (1951), Page (1952), and Yeo (1955).
Many crops such as sugar beets, cotton, and vegetables have low
and unreliable emergence rates. To assure a good stand, these crops
are planted thick and then thinned to desired spacing and stand. AS
RECENT DEVELOPMENTS IN AGRICULTURAL MACHINERY
hand-labor costs have increased, many types of mechanical blockers and
thinners have been developed. The simplest device is the cross-blocker
with a series of rotating knives or sweeps of selected length that is driven
across the row to cut out unwanted plants. Down-the-row thinners follow the direction of the row but have rotary knives that are geared to
the rate of forward movement in such a way as to remove the unneeded
This latter type has received much attention from design engineers.
Blade speed, design, and orientation have been carefully worked out to
provide a high degree of precision and uniformity in the thinning operation. A detailed analysis of the design factors included is given by Richardson (1958). British studies are reviewed by Maughan et al. (1959).
Flame and chemical thinners have been developed but have not been
extensively used. Baggette ( 1949) describes equipment that suspends a
cover over one or more plants at the selected plant-spacing interval; the
remaining plants are then burned out by a flame or sprayed with a direct
The thinners discussed above are all of the random selection type.
One selective-type thinner uses an “electric eye” to locate and examine
the plants. A windowed box containing the phototube is passed over
the row. Light reflected from the first plant actuates the tube. This, in
turn, puts a thinning knife into operation until the tube has located the
next plant at the required distance. The knife then moves aside until it
has passed this “selected” plant. Holmes (1950) indicates that by adjusting the phototube it can be made to select only the larger crop plants,
thus duplicating, to a’degree, the selective ability of a human thinner.
This is a costly device; however, it indicates the unlimited possibilities
that exist for further automation in the field of farm equipment,
V. Developments in Spraying and Dusting Equipment
The increased use of both ground machines and aircraft for the application of agricultural chemicals has been phemonenal in the past
decade, with an estimated use of approximately 260 million dollars worth
of these chemicals on United States farms annually. Major uses are for
insect, disease, weed and brush control, and defoliation.
The type of chemical used has changed in the past ten years from
predominantly dust to spray. An example of the phenomenal growth
in spray equipment is shown by the fact that in 1947 approximately
3000 tractor power-take-off sprayers were manufactured, whereas in 1957
about 60,000 were manufactured. An average of approximately 50,000
T. W. EDMINSTER AND H. F. MILLER, JR.
were manufactured during each of the intervening years. In 1947 one
buyers’ guide listed only five manufacturers of tractor-mounted powertake-off sprayers, but a hundred manufacturers were listed in 1957.
The airplane is considered an agricultural machine for applying spray
and dust materials, since an estimated 5000 planes treat over 60 million
acres annually for pest control, A U. S. Department of Agriculture
(1958~)report on the pesticide situation for 1957-1958 stated: “The
acreage treated by aircraft for pest control in California rose from 296,059
in 1946 to 5,611,000 in 1956, with the area in 1956 almost twice that in
1951.” The U. S. Department of Commerce (1957) gives a breakdown
of aviation application uses for agriculture. The U. S. Department of
Agriculture (1958d) also gives a selected list of references on aircraft
Much progress has been made in the manufacture of spray equipment for both ground machines and aircraft by the use of better materials and manufacturing techniques. Improved nozzles, pumps, valves,
as well as longer-lasting tanks and lines, have come about by the use of
higher-grade metals or newly developed synthetic materials. For instance,
as many as six different types of stainless steel are used in the manufacture of present-day spray equipment. Detailed discussion of the use and
development of spray and dusting equipment is given by Smith (1955)
and Bainer et al. (1955).
Considerable work has been done on the effect of particle and droplet
size when using different chemicals for various purposes. However, researchers are still working for a method to control droplet size and to
produce sprays with a large percentage of droplets in a narrow range
of sizes. Other problems concern methods of increasing the percentage
of material which actually sticks to the plant stem and leaf surfaces, and
ways of measuring these amounts quickly and accurately.
A new photographic and electronic counting method of measuring
spray droplet size has been reported by Farnham (1958) to be a hundred times faster than presently used methods. Brittain et al. (1955)
discuss a relatively simple method of evaluating the deposit on plants,
and Kromer (1949) relates the engineering challenge of spray application. Black (1956) reports on the corrosion and abrasion effects of pesticides on application equipment.
Sprayers for field crops are primarily of three types-tractor-mounted,
tractor-trailed, and high-clearance self-propelled. Orchard sprayers are
generally classified as high pressure or blower (mist) types. Recent developments have been the increased use of self-propelled sprayers for