SECONDARY TILLAGE

SECONDARY TILLAGE
Tillage operations following primary tillage which are performed to create proper soil
tilth for seeding and planting are secondary tillage. These are lighter and finer operations,
performed on the soil after primary tillage operations. Secondary tillage consists of
conditioning the soil to meet the different tillage objectives of the farm. These operations
consume less power per unit area compared to primary tillage operations. Secondary tillage
implements may be tractor drawn or bullock drawn implements.
1. Harrow
Harrow is a secondary tillage implement that cuts the soil to a shallow depth for
smoothening and pulverizing the soil as well as to cut the weeds and to mix the materials
with the soil. There are several types of harrow used in India such as disc harrow, spike tooth
harrow, spring tooth harrow, acme harrow, patela, triangular harrow, bade harrow, guntaka
and reciprocating power harrow.
1.1. Disc harrow
It is a harrow, which performs the harrowing operation by means of a set, or a
number of sets of rotating slat discs, each set being mounted on a common shaft. Disc harrow
is found very suitable for hard ground, full of stalks and grasses. It cuts the lumps of soil,
clods and roots. Disc 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 throws the soil towards left (Fig. 1).
Fig.1. Types of disc harrow
Double action disc 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.1). Thus the entire field is worked twice in
each trip. It may be of two types a) Tandem and b) Off-set.
a) Tandem disc harrow - It is a disc harrow comprising of four gangs in which each gang
can be angled in opposite direction (Fig.2).
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b) Off-set disc harrow- It is a disc harrow with two gangs in tandem, capable of being offset
to either side of the centre line of pull. Two gangs are fitted one behind the other. the soil
is thrown in both directions because discs of both gangs face in opposite directions. (Fig.3).
Fig.2. Tandem disc harrow Fig.3. Offset disc harrow
A disc harrow mainly consists of disc, gang, gang bolt, gang central lever, spool or
arbor bolt or spacer, bearings, transport wheels, scraper and weight box.
i. Disc: It is a circular concave revolving steel plate used for cutting a inverting the soil.
Disc is made of high glass heat-treated hardened steel. Tractor drawn disc harrows have
concave discs of size varying from 35-70 cm diameter. Concavity of the disc affects
penetration and pulverization of soil. Usually two types of disc are used in disc harrows, plain
disc and cut away disc.
ii. Gang: Each set of discs that are mounted on a common shaft is called the gang.
iii. Gang bolt or arbor bolt: It is a long heavy of square headed bolt from the other end,
a set of discs are mounted on the gang bolt. The spacing between the discs on the gang bolt
ranges from 15 to 25 cm for light duty and 25 to 30 cm for heavy-duty harrows.
iv. Gang control lever: A lever, which operates the gang mechanisms of the disc
harrow, is called the gang control lever.
v. Spool or spacer: The flanked tube, mounted on the gang bolt between every two
discs to prevent the lateral movement of the disc on the shaft is called the “spool’ or `spacer’.
vi. Bearing: Bearing is essential to counter act the end thrust of the gang due to soil
thrust. The harrow bearings are subjected to heavy radial and thrust roods chilled cast iron
bearings are used to heavy radial and thrust loads and they are also used due to their
durability.
vii. Transport wheel: In trailing type disc harrow, the transport wheels are provided for
transport work on roads and for preventing the edges of the discs from damage. Mounted
type disc harrows do not require wheels for transport work.
viii. Scraper: It prevents disc from clogging. It removes the soil that may stick to the
concave side of the disc.
ix. Weight box: A box like frame is provided on the main frame of the harrow for
putting additional weight on the implement. Additional weight helps in increasing the
penetration of the disc in the soil.
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A sharp edged disc has more effective penetration compared to blunt edged disc. It is
observed that penetration is better in low speed than in high speed. The following are a few
adjustments for obtaining higher penetration
i. By increasing the disc angle
ii. By adding additional weight in harrow
iii. By lowering the hitch point
iv. By using the sharp edged discs of small diameter and losses concavity
v. By regulating the optimum speed.
1.2. Spike tooth harrow
It is a harrow with peg shaped teeth of diamond cross section to a rectangular frame.
It is used to break the clod, stir the soil, uproot the weeds, level the ground, break the soil and
cover the seeds. Its principle is to smoothen and level the soil directly after ploughing. Spike
tooth harrows may be of rigid type and flexible type. Tractor drawn harrows are usually
flexible type. It has got the advantage of being turned up for transporting purpose (Fig.4.)
This harrow mainly consists of teeth, tooth bar frame, clamps, guard, braces, levers and
hooks.
1.3 Spring tooth harrow
It is a harrow with tough flexible teeth, suitable to work in hard and stony soils.
Spring tooth harrow is fitted with springs having loops of elliptical shape. It gives a spring
action in working condition. It is used in the soil when obstruction like stone, roots and weeds
are hidden below the ground surface. This type pulverizes the soil and helps in killing weeds.
The levers are provided for setting the teeth for varying the depth of harrowing (Fig.5). For
light harrowing, the adjustment is done in slanting position. Draft hooks on each corner of
every section for hitching purpose.
Fig.4. Spike tooth harrow Fig.5. Spring tooth harrow
1.4. Acme harrow
It is a special type of harrow having curved knives. It is also called as knife harrow.
The front part of the knife breaks the soil and crushes the clods (Fig.6). This harrow obtains a
good pulverization. It is good for mulching also.
1.5. Patela
It is a wooden plank used for smoothening the soil and crushing the weeds. It is also
used for breaking clods, packing and levelling the ploughed soil and to remove the weeds. It
is made of a wooden plank with a number of curved steel hooks bolted to a steel angle
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section, which are fixed or hinged to the rear side of the plank (Fig.7). The cutting edge levels
and packs the soil and the curved hooks uproot and collect the weeds.
Fig.6. Acme harrow Fig. 7. Patela
1.6. Triangular harrow
It is a spike tooth harrow with triangular frame (Fig.8). The frame is made of wood
and pointed spikes are fitted in the frame. The teeth of the spikes are fixed and not adjustable.
1.7. Blade harrow (Bakhar)
It is an implement, which consists of one or more blades attached to the beam or
frame, used for shallow working of the soil (Fig.9) with minimum soil inversion. It is used to
prepare seedbeds mostly in clayey soils. It works like a sweep, which moves into top surface
of the soil without inverting the soil.
Fig. 8. Tri angular harrow Fig.9. Blade harrow
1.8. Guntaka
It is an important type of blade harrow. It is an implement, which consists of one or
more blades attached to a frame or beam. It is used for shallow working of the soil with
minimum soil inversion. It is mainly used to prepare the seed bed mostly in clay soils. The
function of Bakhar the same as that of the guntaka.
1.9. Reciprocating power harrow
It is a harrow fitted with rigid tynes driven by the power take off in a reciprocating,
transverse or rotary motion as the machine moves forward. The power tiller harrow is a rear
mounted reciprocatory comb type (fig.10). It has two horizontal oscillating arms having
staggered pegs in two rows at 200 mm spacing. Two sets of slider crank mechanisms provide
power from power tiller PTO through universal joint and bevel gear reduction box to the
arms. An eccentric embedded flywheel actuates the pitman. The two arms move in opposite
directions and hence the implement is dynamically balanced. The amplitude of vibration is
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200 mm and the frequency of operation is 400 cycles per minute. A transport wheel provided
in the rear of the unit ensures depth control. The unit is attached to the power tiller through
the hitch point provided in front portion of the unit. The oscillating pegs breaks the clod,
pulverizes the soil to a fine tilth.
2. Bund former
It is used for making bunds or ridges by collecting the soil. Bunds are required to
hold water in the soil, thereby one can conserve moisture and prevent run-off. The size of the
bund former is determined by measuring the maximum horizontal distance between the two
rear ends of the farming boards. Bund former consists of forming board, beam and handle
(Fig.11).
Fig. 11. Bund former
3. Ridger
It is an implement importantly used to form ridges required for sowing row crop seeds
and plants in well-tilled soil. The ridger is also used for forming field or channels, earthing
up and similar other operations. Ridger is also known as ridging plough and double mould
board plough. The ridger generally has ’V’ shaped or wedge shaped share fitted to the frog.
The nose or tip of share penetrates into the soil and breaks the earth. The mould boards lift,
invert and also cast aside the soil, forming deep channels and ridges of the required size. A
ridger consists of beam, clevis, frog, handle, mould boards, share and sliding share.
4. Puddler
Puddler is an implement for churning the soil with water. It is used to prepare paddy
fields with standing water after initial ploughing with country plough. It breaks up the clods
and churns the soil. The main purpose of puddling is to reduce leaching of water or decrease
Fig.10. Reciprocating Harrow
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percolation of water, to kill the weeds by decomposition and to facilitate transplantation of
paddy seedlings by making the soil softer. Puddling is done in standing water of 5-10 cm
depth. A common puddler has puddling units each having four straight blades or paddles or
fan type blades or squirrel type blade mounted on an axle. The axle with the puddling units is
fully mounted on two bearings fitted on a frame made of metal or wood. The weight of the
puddler is 30-40 kg. A puddler consists of a frame, puddling unit, axle, metal cross beam and
handle.
5. Leveller
Land levelling is expected to bring permanent improvement in the value of land.
Levelling work is carried out to modify the existing contours of land so as to achieve certain
objectives desired for efficient agricultural production system. These objectives include
(i) efficient application of irrigation water,
(ii) improved surface drainage,
(iii) minimum soil erosion
(iv) increased conservation of rain water specially on dry lands and
(v) provision of an adequate field size and even topography for efficient mechanisation.
6. CULTIVATORS
It is an implement for inter cultivation with laterally adjustable tines or discs to work
between crop rows. The cultivator stirs the soil, and breaks the clods. The tines fitted on the
frame of the cultivator comb the soil deeply in the field. A cultivator performs functions
intermediate between those of plough and the harrow. Destruction of weeds is the primary
function of a cultivator. The following are a few important functions performed by a
cultivator.
1. Interculture the fields.
2. Destroy the weeds in the field.
3. Aerate the soil for proper growth of crops.
4. Conserve moisture by preparing mulch on the surface.
5. To sow seeds when it is provided with sowing attachments.
6. To prevent surface evaporation and encourage rapid infiltration of rain water
into the soil.
The cultivator can be 1) Disc cultivator, 2) Rotary cultivator, 3) Tine cultivator.
Disc cultivator : It is a cultivator fitted with discs.
Rotary cultivator : It is a cultivator with tines or blades mounted on a power driven
horizontal shaft.
Tine cultivator : It is a cultivator fitted with tines having shovels.
Tractor Drawn Cultivator
Trailed type cultivator
It consists of a main frame which carries a number of cross members to which tines
are fitted. At the forward end of the cultivator, there is a hitch arrangement for hitching
purpose. A pair of wheels are provided in the cultivator. The height of the hitch is adjusted so
that main frame remains horizontal over a range of depth setting. The tines in each row are
spaced widely to allow free passage of the soil and trash around them. The tines in
subsequent rows are staggered so that the implement can cover the entire width nicely.
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Mounted Cultivator
Tractors fitted with hydraulic lift operate the mounted type cultivators. A rectangular
frame of angle iron is mounted on three point hydraulic linkage of the tractor. The cross
members carry the tines in two staggered lines. Depending upon the type of soil and crop,
shovels are chosen for use on the cultivators. Usually tractor drawn cultivators are of two
types, depending upon the flexibility and rigidity of tines (i) Cultivator with spring loaded
tines (ii) Cultivator with rigid tynes.
Cultivator with spring loaded tines
A tine hinged to the frame and loaded with a spring so that it swings back when an
obstacle is encountered, is called spring loaded line. Each of the tine of this type of cultivator
is provided with two heavy coil springs (Fig. 12), pre-tensioned to ensure minimum
movement except when an obstacle is encountered. The springs operate, when the points
strike roots or large stones by allowing the tines to ride over the obstruction, thus preventing
damage. On passing over the obstruction, the tines are automatically reset and work continues
without interruption. The tines are made of high carbon steel and are held in proper alignment
on the main frame members. This type of cultivator is particularly recommended for soils
which are embedded with stones or stumps.
Fig. 12. Tractor drawn cultivator
Cultivator with rigid tines
Rigid tines of the cultivators are those tines which do not deflect during the work in
the field. The tynes are bolted between angle braces, fastened to the main bars by sturdy
clamps and bolts . Spacing of the tines is changed simply by slackening the bolts and sliding
the braces to the desired position. Since rigid tines are mounted on the front and rear tool
bars, the spacing between the tynes can be easily adjusted without getting the tines choked
with stubbles of the previous crop or weed growth. A pair of gauge wheel is used for
controlling the depth of operation.