It is the minimum soil manipulation necessary
to meet tillage requirements for crop production
Strip Tillage
It is a tillage system in which only isolated
bands of soil are tilled.
Rotary Tillage
It is the tillage operations employing
rotary action to cut, break and mix the soil.
Mulch Tillage
It is Preparation of soil in such a way
that plant residues or other mulching materials are specially left
on a near the surface.
Combined Tillage
Operations simultaneously utilizing two
or more different types of tillage tools or implements to simplify,
control or reduce the number of operations over a field are called
combined tillage. Tillage is performed by tool, implement or machine.
Tool
It is an individual working element such
as disc or shovel.
Implement
It is equipment generally having no driven
moving parts, such as harrow or having only simple mechanism such
as plough.
Machine
It is a combination of rigid or resistant
bodies having definite motions and capable of performing useful work.
A mouldboard plough is very common implement used for primary
tillage operations (Fig. 2).
This plough performs several functions at a time.
Functions
cutting the furrow slice
lifting the soil
turning the furrow slice and
pulverising the soil.
Components
M.B. Plough consists of (Fig. 3):
Share (b) Mouldborad (c) Land side (d) Frog and (e) Tailpiece.
Share
It is that part of the plough bottom which penetrates into the soil
and makes a horizontal cut below the surface.
Mouldboard
It is the curved part which lifts and turns the furrow slice.
Land side
It is the flat plate which bears against and transmits the rear side
lateral thrust of the plough bottom to the furrow wall.
Frog
It is the part to which other components of the plough bottom are
attached.
Tail piece
It is an adjustable extension, which can be fastened to the rear
of a mould board to help in turning a furrow slice.
Share
It penetrates into the soil and makes a horizontal cut below the soil
surface (Fig. 4).
It is sharp, well-polished and pointed component. Different portions
of the share are called by different names such as:
(1) Share point (2) Cutting edge (3) Wing of share (4) Gunnels (5)
Cleavage edge and
(6) Wing bearing.
Share point
It is the forward end of the cutting edge which actually penetrates
into the soil (Fig. 4)
Cutting edge
It is the front edge of the share which makes horizontal cut
in the soil (Fig. 4). It is beveled to some distance.
Wing of share
It is the outer end of the cutting edge of the share. It supports
the plough bottom (Fig. 4).
Gunnel
It is the vertical face of the share which slides along the
furrow wall. It takes the side thrust of the soil and supports
the plough bottom against the furrow wall (Fig. 4).
Cleavage edge
It is edge of the share which forms joint between mouldboard
and share on the frog (Fig. 4).
Wing bearing
It is the level portion of the wing of the share, providing
a bearing for the outer corner of the plough bottom.
Material of share
The shares are made of chilled cast iron or steel. The steel
mainly contains about 0.70 to 0.80% carbon and about 0.50 to 0.80%
manganese besides other minor elements.
Type of share
Share is of different types such as:
Slip share
Slipnose share
Shin share and
Bar point share.
Slip share
It is one piece share with curved cutting edge, having no additional
part.
It is a common type of share, mostly used by the farmers, It is
simple in design, but it has got the disadvantage that the entire share
has to be replaced if it is worn out due to constant use (Fig. 5a).
Slipnose share
It is a share in which the point of share is provided by a small detachable
piece.
It has the advantage that share point can be replaced as and when
required.
If the point is worn out, it can be changed without replacing the
entire share, effecting considerable economy (Fig. 5b).
Shin share
It is a share having a shin as an additional part.
It is similar to the slip share with the difference that an extension
is provided to it by the side of the mouldboard (Fig. 5c).
Bar point share
It is a share in which the point of the share is provided by an adjustable
and replaceable bar.
This bar serves the purpose of point of the share and land side of
the plough (Fig. 5d).
Mouldboard
The mouldboard is that part of the plough which receives the furrow
slice from the share.
It lifts, turns and breaks the furrow slice.
To suit different soil conditions and crop requirements, mouldborad
has been designed in different shapes.
The mouldboard is of following types: (a) General purpose (b) Stubble
(c) Sod or Breaker and (d) Slat.
General purpose
It is a mouldboard having medium curvature lying between stubble and
sod.
The sloping of the surface is gradual (Fig. 6a).
It turns the well-defined furrow slice and pulverizes the soil thoroughly.
It has fairly long mouldboard with a gradual twist, the surface being
slightly convex.
Stubble type
It is a short but broader mouldboard with a relatively abrupt curvature,
which lifts breaks and turns the furrow slice used in stubble soils.
It curvature is not gradual but it is abrupt along the top edge
(Fig. 6b).
This causes the furrow slice to be thrown off quickly, pulverising
it much better than other types of mouldboard.
This is best suited to work in stubble soil that is under cultivation
for years together. Stubble soil is that soil in which stubble of the
plants from the previous crop is still left on the land at the time
of ploughing.
This type of mouldborad is not suitable for lands full of grasses.
Sod or Breaker type
It is a long mouldboard with gentle curvature which lifts and inverts
the unbroken furrow slice (Fig. 6c).
It is used in tough soil of grasses.
It turns over thickly covered soil.
This is very useful where complete inversion of soil is required by
the farmer.
This type has been designed for use in sod soils.
Slat type
It is a mouldboard whose surface is made of slats placed along the
length of the mouldboard so that there are gaps between the slats (Fig.
6d).
This type of mouldboard is often used, where the soil is sticky, because
the solid mouldboard does not scour well in sticky soils.
Land side
It is the flat plate which bears against and transmits lateral
thrust of the plough bottom to the furrow wall.
It helps to resist the side pressure exerted by the furrow slice on
the mouldboard.
It also helps in stabilizing the plough while it is in operation.
Land side is fastened to the frog with the help of plough bolts.
The rear bottom end of the land side is known as heel which rubs
against the furrow sole.
Frog
Frog that part of the plough bottom to which the other components
of the plough bottom are attached (Fig. 7).
It is an irregular piece of metal. It may be made of cast iron for
cast iron ploughs or it may be welded steel for steel ploughs.
Tail piece
It is an important extension of mouldboard which helps in turning
a furrow slice.
Plough accesories
There are a few accessories necessary for ploughs such as: (i)
Jointer (ii) Coulter (iii) Gauge wheel (iv) Land wheel and (v) Furrow
wheel.
Jointer
It is a small irregular piece of metal having a shape similar to an
ordinary plough bottom.
It looks like a miniature plough. Its purpose is to turn over a small
ribbon like furrow slice directly in front of the main plough bottom.
This small furrow slice is cut from the left and upper side of the
main furrow slice and is inverted so that all trashes on the top of
the soil are completely turned down and buried under the right hand
corner of the furrow slice is cut from the left and upper side of the
main furrow slice and is inverted so that all trashes on the top of
the soil are completely turned down and buried under the right hand
corner of the furrow.
Coulter
It is device used to cut the furrow slice vertically from the land
ahead of the plough bottom.
It cuts the furrow slice from the land and leaves a clear wall.
It also cuts trashes which are covered under the soil by the plough.
The coulter may be: (s) Rolling type disc coulter or (b) Sliding type
knife coulter.
Rolling type disc coulter
It is a round steel disk which has been sharpened on the edge and
suspended on a shank and yoke from the beam.
The edge of the coulter may be either smooth or notched.
It is so fitted that it can be adjusted up-down and side ways.
The up-down adjustment takes care of depth and sideways adjustment
is meant for taking care of width of cut.
Sliding type knife coutler
It is a stationary knife fixed downward in a vertical position on
the beam.
The knife does not roll over the ground but slides on the ground.
The knife may be of different shapes and sizes.
Gauge wheel: It is an auxiliary wheel of an implement to maintain
an uniform depth
of working.
Gauge wheel helps to maintain uniformity in respect of depth of
ploughing in different soil conditions.
It is usually placed in hanging position.
Land wheel
It is the wheel of the plough which runs on the unploughed land.
Front furrow wheel
It is the front wheel of the plough which runs in the furrow.
Rear furrow wheel
It is rear wheel of the plough which runs in the furrow.
It is a plough which cuts, turns and in some cases breaks furrow
slices by means of separately mounted large steel discs.
A disc plough is designed with a view to reduce friction by making
a rolling plough bottom instead of sliding plough bottom.
A disc plough works well in the conditions where mouldboard plough
does not work satisfactorily.
Advantages of disc plough
A disc plough can be forced to penetrate into the soil, which is
too hard and dry for working with a mouldboard plough.
It works well in sticky soil in which a mouldboard plough does not
occur.
It is more useful for deep ploughing.
It can be used safely in stony and stumpy soil without much danger
of breakage.
A disc plough works well even after a considerable part of the disc
is worn off in abrasive soil.
It works in loose soil also (such as peat) without much clogging.
Disadvantages of disc plough
It is not suitable for covering surface trash and weeds as effectively
as mouldboard plough does.
Comparatively, the disc plough leaves the soil in rough and more
cloudy condition than that of mouldboard plough.
Disc plough is much heavier than mouldboard plough for equal capacities
because penetration of this plough is affected largely by its weight
rather than suction.
There is one significant difference between mouldboard plough and
disc plough i.e. mouldboard plough is forced into the ground by the
suction of the plough, while the disc plough is forced into the ground
by its own weight.
Types of disc plough
Disc ploughs are of two types:
(i) Standard disc plough and (ii) Vertical disc plough.
Standard disc plough
It consists of steel disc of 60 to 90 cm diameter, set at a certain
angle to the direction of travel. Each disc revolves on a stub axle
in a thrust bearing, carried at the lower end of a strong stand which
is bolted to the plough beam (Fig. 8).
The angle of the disc to the vertical and to the furrow wall is
adjustable.
It action, the disc cuts the soil, breaks it and pushes it sideways.
There is little inversion of furrow slice as well as little burying
of weeds and trashes.
The disc plough may be mounted type or trailed type. In mounted disc
plough, the wheels of the tractor take the side thrust.
Sometimes a rear wheel is fitted to take side thrust of the plough
to some extent.
It trailed type; the furrow wheel of the plough takes side thrust.
Disc is made of heat-treated steel of 5 mm to 10 mm thickness.
The edge of the disc is well sharpened to cut the soil.
The mount of concavity varies with the diameter the disc.
The approximate values being 8 cm for 60 cm diameter disc and 16 cm
for 95 cm diameter.
A few important terms connected with disc plough explained below:
Disc
It is a circular, concave revolving steel plate used for cutting
and inverting the soil.
The rotovator
It consists of 16 curved tines bolted on a horizontal power
driven shaft.
On this shaft 8 times are bent at edge in right hand side and
another eight in the left hand side.
The times are so arranged to give uniform cutting load on the shaft.
Rotovator ploughs, pulverises mixes and levels dry and wet lands.
Rotovator is used for pudding also in the previously ploughed land.
It replaces cultivator, disc harrow and puddler.
It converts crop residuals as manure.
Rotovator offers a package of benefits to the farmers like getting
a better seed bed, weed control, improvement of humus content and soil
structure.
As with moldboard ploughs, disc ploughs are also classified by (1)
their method of hitching to the tractor (i.e., direct mounted, semi-mounted
and trailing) and (2) whether to plough is reversible or not.
Integral mounted ploughs
They are usually to the tractor by three-point linkages.
They can be raised or lowered by the hudraulic system.
Most can be attached in less than a minute.
They are usually rear-mounted and have a rear wheel to absorb
the side thrust.
But some are mounted ahead of the rear wheels.
A rear furrow wheel on an integral mounted disc plough may serve to
counteract side pressures, hold the plough in alignment, and act as a
gage wheel for ploughing depth.
The depth in some makes is controlled by adjusting the hydraulic lift.
Semi-mounted disc plough
The semi-mounted disc plough is also called a direct-connected blow.
The front of this plough is connected to and mounted on the tractor,
thus diminating the front furrow wheel and the land wheel (See Figure
120).
A furrow steel supports the rear end.
This close-coupled plough is compact and easy to handle.
It is easy to maneuver because short turns can be made, enabling
the operator to close to fences.
It can also be backed into corners.
The rear wheel is automatically controlled from the steering mechanism
at the front of the plough hydraulic lift raises the front of the plough
high enough so it can be turned and transported easily.
Development History
Although there has been a marked increase of interest in rotary plough
and tillers in the United States during the last few years, the principle
of rotary tillage is not new.
Patents on devices of this type were issued as early as 1850-1860,
but it was not until about 1910 that a successful rotary tiller using
the elastic-claw principle with a staggered arrangement, was developed
by Von Meyenberg of Switzerland.
Swissrade rotary ploughs or tillers were introduced into the United
States in about 1930, and soon afterwards several American manufacturers
started making this type of equipment.
It has only been rather recently that this type of tillage has experienced
any real interest. The reason for the lack of interest was high cost,
high power requirements and poorer weed control.
A harrow is an implement that cuts the soil to a shallow depth
for smoothening and pulverising the soil as well as to cut the weeds
and to mix materials with soil.
It is an implement used to break the clods after ploughing, to collect
trash from the ploughed and to level the seed bed.
Harrowing
It is secondary tillage operation which pulverises, smoothens
and packs the soil in seed bed preparation and / or control weeds.
There are several types of harrow used in India, such as:
Disc harrow
Triangualr harrow
Spring tooth harrow
Bodela
Spike tooth harrow
Zig-zag harrow
Blade harrow (Bakhar)
Bindha
Guntaka
Other harrows.
Disc harrow
It is a harrow which performs the harrowing operations by means
of a set (or a number of sets) of rotating steel discs, each set being
mounted on a common shaft. Disc harrows are of two types depending upon
the sources of power. (a) Tractor drawn
(b) Animal drawn.
Tractor drawn disc harrow
Disc harrow is found very suitable for hard ground, full of stalks
and grasses.
It cuts the lumps of soil, clods and roots. Discs are mounted on one,
two or more axles which may be set at a variable angle to the line of
motion.
As the harrow is pulled ahead, the discs rotate on the ground.
Depending upon the disc arrangements, disc harrows are divided into
two classes: (a) Single action and (b) Double action.
Single action disc harrow
It is a harrow with two gangs placed end to end, which throw the
soil in opposite directions.
The discs are arranged in such a way that right side gang throws the
soil towards right, and left side gang shows the soil towards left (Fig.
11).
Double action harrow
A disc harrow consisting of two or more gangs, in which a set of one
or two gangs follow behind the set of the other one or two, arranged
in such a way that the front and back gangs throw the soil in opposite
directions (Fig. 11).
Thus the entire field is worked twice in each trip.
It may be of two types: (a) Tandem and (b) Off-set.
Tandem disc harrow
It is a disc harrow comprising of four gangs in which each gang can
be angled in opposite direction (Fig. 12).
Off-set disc harrow
It is a disc harrow with two gangs in tandem, capable of being off-set
to either side of the centre line of pull.
Two gangs are fitted one behind the other (Fig. 12).
The soil is thrown in both directions because discs of both gangs
face in opposite directions.
It is very useful for orchards and gardens.
It travels left to right of the tractor.
The line of pull is not in the middle, that's why it is called off-set
disc harrow (Fig. 13).
Off-set disc harrow is based on the basic principle that side thrust
against the front gang is opposed by the side thrust of the rear gang.
Hence the gangs are arranged at suitable angles so that both thrusts
are counter balanced with each other.
It is an implement used for churning the soil in standing water.
Puddler is used for preparation of paddy fields with standing water
after initial ploughing.
It breaks up the clods and churns the soil.
The main purpose of puddling is to reduce leaching of water, to kill
weeds by decomposing and to facilitate the transplanting of paddy seedlings
by making the soil softer.
Puddling is done in a standing water of 5 to 10 cm depth.
A common puddler used in this country has three puddling units, each
having four paddles mounted on a axle (Fig. 14).
The axle with the puddling units is freely mounted on two bearing,
fitted on a frame, made of metal or wood.
The weight of the puddler including its beam is within range of 30
to 40 kg only.
Tillage is the preparation of the soil for planting and the process
of keeping it loose and free from weeds during the growth of crops.
The primary objectives of fundamental purposes of tillage are divided
into three phases: (1) to prepare a suitable seedbed, (2) to destroy
competitive weeds and (3) to improve the physical condition
of the soil.
The basic tillage operation is the breaking of the soil in the
preparation of a suitable seedbed.
The breaking and loosening of the soil is the oldest phase of village
as it includes the various types of plows.
Prehistorically, it is assumed that man used crude tools of wood or
other material with which he could loosen the soil.
Perhaps a broken branch of a tree was the first tillage tool available.
Later he learned to use fire or stone hand tools to fashion a soil-strirring
tool from a fork of a tree by burning or hacking off one branch, leaving
the longer for the beam and the trunk part for a handle.
Still later, he was able to use miral power to pull the plow.
History of the Plow
The plow is probably the oldest agricultural tool.
The recorded history in the form of hieroglyphs and cuneiform characters
shows that the ancients had a plow thousands of years B.C.
It is recorded that about 900 B.C.
Elisha as found "plowing with twelve yoke of oxen before him".
The wooden plow with a metal share has been used for many centuries,
and millions of wooden plows are still is use today.
The parts of the wooden plow were usually held together by animal
thongs as there were no nails, bolts, or haywire available.
The Roman plow which was improved by the Dutch, was imported into
England about 1730.
The Ensex plow of about 1756 had an iron moldboard.
The Norfolk sheel plow of 1721 had a cast-iron share and an iron rounded
moldboard.
A curved moldboard made its appearance in 1760 on the Suffolk swing
plow.
The Rotherham plow was improved by James Small, who wrote a book on
plow design in 1984.
The close of the eighteenth century saw the chage in England from
the wooden plow to the iron plow.
In American, Thomas Jefferson and Daniel Webster were among the
first to advance improvements of the plow.
Charles Newbold of Burlington, New Jersey, secured the first patont
on a cast-iron plow in 1797.
Farmers rejected this iron plow because say thought it poisoned the
soil; Jethro Wood developed a moldboard in 1814 of such curvature as
to turn the soil in even furrows.
The first steel plow was made from three sections of an old handsaw
by John Lane about 1833.
He also secured in 1868 a patent for soft-center steel, which is
used at the present time in making moldboard for plows. In 1837, John
Deere at Grand Detour, Illinois, made a steel plow (share and moldboard
in one piece) from an old sawmill saw.
Ten years later be established factory at Moline, Illinois.
James Oliver was granted a patent in 1868 for hardening cast iron
which was own as chilled iron.
In 1856, M. Furley patented a single-bottom sulky or wheel plow
which permitted the operator to ride.
In 1864, F.S. Davenport patented a riding two-bottom horse drawn
gang plow.
Three-and four-bottom gang plows often required ten to twelve horses
to pull them.
The large ten-to fifteen-bottom plows were pulled by steam tractors
in the 1890's by the large, slow, cumbersom gasoline-engine tractors
from about 1900 to 1910.
The early two-to five-bottom trailing-tractor plows were equipped
with hand-lever lifts.
In the early twenties, mechanical power lifts were developed.
They were used until the hydraulic lift was introduced in the forties.
The integral tractor-mounted unit assembly and unit-lifted plow were
developed in the early forties by Ferguson.
This type of plow is now becoming popular on small and average sized
farms.
The disk-plow
was probably developed about 1890. Models were listed in implement
catalogues by 1895.
One of the earliest patents for a disk plow was secured by M.A. and
I.M. Cravath, Bloomington, Illionois. J.K. Underwood, D.H. Lane, and
M.T. Hancock made improvements on the disk plow and made it practical.
Since 1900, the development of the disk plow has followed trends similar
to that of the moldboard plow.
Influence of the Plow on Man
When man grasped a crooked stick and began to till the soil, he took
his first step toward civilization.
With each phase in the development of the plow, there has been a
corresponding advance in civilization.
In the beginning, one man, even though he gave all his time and energy
to the task, could till only a small acreage.
Later, animal power was applied and the acreage per man was increased.
Now, with the large amount of mechanical power available, the acreage
per man has been very materially increased.
Thus, man can now produce more foods tuff than is necessary for his
own sustenance and can furnish food to many who are working at other
tasks.
Hence, we can say that the flow is the foundation of civilization.
In the production of all kinds of crops and in the preparation of
a seedbed for them, the plow is the first tool used, and it is thus
the basic tool of the farm.
With the plow the ground is broken and pulverized into small particles,
trash on the surface may be left on the surface or completely covered.
One not familiar with the nature of the soil, the influence of water,
air, and temperature upon its physical condition, and the action of
the plow upon it may think that the plow is a very simple tool, requiring
very little adjustment and practically no care at all.
But those who are familiar with soil conditions and the plow adjustments
necessary to obtain the best results know that good planning is not
a simple matter.
Optimum plowing requires the consideration of numerous factors.
The following paragraphs suggest ways in which minimum tillage
can be accomplished.
Primary and secondary tillage, as well as planting, are operations
that an be accomplished simultaneously under certain conditions.
It is economically convenient and less soil compaction occurs, but
some other factors may indicate the convenience of performing these
operations at different times.
plough Packer
This minimum tillage operation uses a roller packer behind the
mouldboard plough, Both implements are operated by the same tractor.
The plough-packer works best on loam and lighter soils having some
cover other than heavy sod.
The plough packer does as little tillage as any of the once-over implements.
Experiments, however, have shown that it is sufficient as long as
adequate crop stands are obtained.
This tiller is especially good for heavy soils.
The blades press the furrows down and exert some packing below the
surface.
At the same time, the tune does some smoothing.
This action does more to correct ploughing defects than the plough packer.
Draft is about twice that needed for the packer.
The packer can also be used in front of the planter during the
next operation, but it is not so effective because the clods are drier
and harder to break.
A spite harrow can also be used instead of the packer.
It can do a good if its width is twice that of the plough so as to cover
the soil twice.
The spike harrow is known by all farmers, and most of them have one
probably discarded.
One section makes a good light-draft minimum tillage implement.
The teeth must be set slanting so the frame drags and levels the
soil.
It is convenient to hitch the harrow in such a way that it is lifted
together with the plough.
It is important because spike harrows collect trash.
The rotary hoe, run backward, serves very wall as a minimum tillage
tool.
It crumbles lumps and presses down partly turned furrows.
The rotary hoe, run backward, does a little presenting of furrows
and breaks soft lumps.
In amount of tillage performed and in draft, it compares favorably
with the plough packer.
The circular tiller
Ttills and firms the soil by the turning action of a wheel which lies
almost flat on the ground.
The slight pitch of the wheel causes it to turn.
A small gauage wheel holds it in position.
Figure 39.
This circular tiller revolves as it is pulled behind the plough.
You can add weight to the wheel for more firming.
The spring tooth harrow
it does not do a satisfactory job because it pulls up trash and grass.
On the other hand, the draft is considerably higher than for any of
the tools described above.
plough packer with grain drill
A grain drill covering just the width of the plough is hitched behind
the plough packer unit described before.
It works well when ploughing can be done at planting times. In some
cases the soil may be too dry at that time for ploughing.
Heavy compacted soils may have to be ploughed some time before planting
in order to store some water for germination and the first stage of
plant growth.
self-propelled units (two wheel, 8 to 30 inches wide and 6 to 15
H.P. engines).
The garden-type rotary tillers have proved themselves practical and
effective for preparing seedbeds from unploughed ground for nurseries,
greenhouses, vegetable crops, lawn planting, and similar jobs.
These narrow machines are also suitable for shallow cultivation and
weed control between rows of certain crops.
Trailed or tractor-mounted units with p.t.o. drives
This type is usually 3 to 4 feet wide and requires 10 to 15 horesepower
for each foot of width.
The cutting knives or tines are generally mounted on a horizontal
power driven shaft which operates at about 300 r.p.m.
The knives on some machines are provided with a shock-cushioned friction
clutch that prevents the knives from breaking when they come in contact
with a rock o solid obstacle.
Trailed units with auxillary engines
This rotary tiller is pulled forward by a tractor but has the cutting
knives driven by an auxillary engine mounted on the frame of the plough.
This type of plough is made in 4 to 7-foot sizes and requires 60 to
100 horsepower.
The cutting knives are mounted on a horizontal power-driven shaft.
Field-type, self-propelled machines (0 to 8 ft. cut, with
engines as large as 180 h.p.
Rotary tillers may also be classified by the position of the soil
engaging rotor.
Most of the rotary tillers used in the United States have a horizontal
axis for the rotating knives
In Europe, tillers with a vertical axis for the rotating knives are
also common
There are some differences in the designers of frame work and
drive mechanism to the two types.
There are also some slight differences in their particular use of
operation, but basically they do the same job and have the same limitations.
Development
The disc tiller is also called the disc-plough, vertical disc-plough,
one-way disc-plough, harrow plough, Wheatland plough, cylinder plough, tiller
disc-plough and one-way disc. i.e. consider "disc tiller" the most suitable
name.
The disc tiller was developed in the Great Plains area of the United
States about 1927. It was designed primarily as a one-way disc harrow.
As its use spread, farmers began to adopt it for shallow ploughing. Improvements
have made the tool into a popular and widely used plough.
The speed of the plough should not be over 4 m.p.h. High-speed operation
increases the power requirements, causes too much pulverizing of the
surface soil, and does not leave trash on the surface to prevent wind
erosion.
This implement is about halfway between the standard disc-plough and
the disc harrow in its soil working actions.
It carries the discs at approximately a 45-degree angle to the travel
direction cutting the throwing all the soil in the same direction. The
discs are smaller than on a disc-plough, usually 16 to 24 inches in diameters,
and have no scrapers to assist in inverting the soil.
They cut shallower and narrower than those on the disc-plough, usually
making a cut approximately 4-inches in width. They mix the soil with
the trash instead of inverting the furrow slice and covering the trash.
This mixing action retards drifting and blowing and keeps the soil
in excellent condition to receive and hold moisture. Because the disc
tiller is primarily a mixing tool, the draft is lower per foot than
with the disc-plough.
Thus the same power, can pull a wider implement, cover more ground,
and work faster than with the disc-plough. Where trash mixed through the
top soil is not objectionable and where it is not necessary to work
the soil deeply, a disc tiller can be substituted for a disc or moldboard
plough.
As the name Wheatland suggests, these implements were originally developed
for the preparation of wheat land. The disc tiller is not a universal
tool like the moldboard plough; it is limited to certain regions.
The term secondary tillage in this discussion
means stirring the soil at a comparatively shallow depth (0 to 6 inches).
The action of the plough does not usually prepare an ideal seedbed.
Unless the plough is working in an ideal, mellow soil, further pulverization
of the soil will generally be necessary before planting.
As the young plants develop certain amounts of cultivation and weed
eradication will be required.
The equipment used to perform these operations are known as secondary
tillage implements.
The first implements to prepare the soil for sowing probably originated
simultaneously with primitive ploughs.
They were dry branches of various shapes drawn by men or occasionally
by animals.
It was not until the Roman era that the toothed harrow with wooden
teeth (Fig. 151) appeared.
In time, the shape of the harrow frame was altered.
In the Middle Ages, harrows consisting of several bars tied crosswise
were used. at the beginning of the nineteenth century, wooden harrows
with rigid tines were produced on the pattern of harrows with spring
tines.
At the end of the nineteenth century cultivators for deep tillage
were designed and were used to replace ploughs to some extent.
The first patent for a disc harrow in the United States was obtained
in 1867.
About then the Higganum Corporation at Higganum, Connecticut, began
making disc harrows commercially.
The disc blades used before 1886 were all plain, perfectly smooth
around the edge.
In that year, George N. Clark, president of the Higganum Corporation,
cut curved ntoches in the rim of the discs and used the term "cutway"
to describe this disc harrows.
Regular disc harrows, had become quite popular by 1900.
In 1925, the offset disc harrow was designed to work under the branches
of fruit trees.
The general objectives are
To improve the seedbed by greater pulverization of the soil.
To conserve moisture by summer-fallow operations to kill weeds and
reduce evaporation.
To cut up crop residue and cover crops and mix vegetable matter with
the top soil.
To break up clods, firm the top soil and put it in better tilth for
seeding and germination of seeds.
To destroy weeds on fallow lands.
In general a good secondary tillage operation is possible after proper
adjustment. An even better job is dependent upon the attention shown
to the operation by the operator. The pictures below give an idea of
a desirable soil consistency after harrowing.
