🚋Tillage Implements — Primary and Secondary

The plough — invented around 2900 BC — was humanity’s first step towards systematic agriculture. Today, farmers choose from a toolkit of tillage implements: mould board ploughs for deep inversion, disc ploughs for hard soils, sub-soilers for breaking compacted layers, and rotavators for fine seed bed preparation. Selecting the right implement for the right soil condition is a skill every agricultural professional must master.

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Primary Tillage Implements

• The initial major soil working operations designed to plough the soil deeply to reduce soil strength, cover plant materials and rearrange aggregates is called primary tillage. This is the first and most energy-intensive tillage operation performed on the land after crop harvest. It sets the foundation for all subsequent field operations.

• Tractor drawn implements include mould-board ploughs, disc ploughs, heavy duty disk harrows, subsoiler, chisel ploughs etc.

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Ploughs

• Plough was invented during 2900 BC, making it one of the oldest agricultural implements in human history. From simple wooden sticks to modern steel ploughs, the evolution of the plough mirrors the progress of agriculture itself.

• The main implement which is used for primary tillage is Plough used for ploughing operations.

• Ploughing is the primary tillage operation which is performed to cut, break and invert the soil partially or completely. Inversion buries crop residues and weeds, exposing the lower soil layer for weathering by sun and air.

• Iron plough was invented by James Small. This was a significant advancement over wooden ploughs as it could cut deeper and turn soil more effectively.

• Normal ploughing under primary tillage operation is usually done up to 15 cm depth.

• Vertical suction/clearance: Adjustment for depth control in M.B. plough. It is the distance between the lowest point of the share and the ground surface, causing the plough to penetrate the soil. More vertical suction means deeper penetration.

• Horizontal suction/Side clearance: This suction helps M.B. plough to cut the proper width of furrow slice. It ensures the plough moves slightly into the unploughed land, maintaining consistent furrow width.

• Through clearance: It is the perpendicular distance between the point of share and the lower position of the beam of the plough. Adequate through clearance prevents trash from clogging between the beam and the soil surface.

• Pull: total force required to pull an implement.

• Draft: Horizontal component of the pull, parallel to line of motion. Draft is the actual force the tractor needs to exert to move the implement through the soil. It directly determines the power requirement.

• Side draft: Horizontal component of the pull, perpendicular to line of motion. Excessive side draft causes the tractor to steer sideways and results in uneven wear on the implement.

• Unit draft: Draft per unit area of soil cross-section. It helps compare the resistance offered by different soil types and is used for matching implements to tractor power.

• Effective field capacity: It is the actual area covered by implements, based on its total time consumed and its width (ha/hr). This includes time lost in turning, adjustments, and refueling.

• Theoretical field capacity: It is the theoretical area covered by implements, based on its total time consumed and its width (ha/hr). It assumes continuous operation without any time losses.

• Field Efficiency = (Effective field capacity/Theoretical field capacity) x 100. A higher field efficiency indicates fewer time losses during operation. Typical field efficiency ranges from 60-85% depending on the implement and field conditions.

• Soil pulverization is quality of work in terms of soil aggregates and clod size. This is measured by Penetrometer. Good pulverization means the soil is broken into fine, uniform aggregates suitable for seed germination.

• Cohesion: Force of attraction between similar particles (e.g. soil and soil). Cohesion holds soil particles together and determines soil strength.

• Adhesion: Force of attraction between dissimilar particles (e.g. soil and metal). Adhesion causes soil to stick to plough surfaces, increasing draft requirements. This is why scrapers are used on disc ploughs.

• Gathering: Whenever a plough works round a strip of ploughed land, it is said to be gathering. The furrow slices are turned towards the centre ridge.

• Casting: Whenever a plough works round a strip of un-ploughed land, it is said to be casting. The furrow slices are turned away from the centre, creating an open furrow in the middle.

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• Certain important terms related with ploughing of land:
  • Furrow: A trench formed by an implement in the soil during the field operation.
  • Furrow slice: The mass of soil cut, lifted and thrown to one side.
  • Furrow wall: An undisturbed soil surface by the side of a furrow.
• Crown: The top portion of the turned furrow slice.
• Back furrow: A raised ridge left at the centre of the strip of land when ploughing is started from centre to side.
• Dead furrow: An open trench left in between two adjacent strips of land after finishing the ploughing. Dead furrows can cause problems in irrigation if not managed properly, as water tends to accumulate in them.

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Types of plough

The different types of ploughs are as follows:

• Indigenous plough — traditional wooden plough used since ancient times, still found in parts of India.
• Mould board plough — inverts the soil completely, best for burying crop residues and weeds.
• Disc plough — uses rotating discs, ideal for hard and dry soils where mould board ploughs cannot work.
• Chisel plough — breaks up compacted soil layers without full inversion, preserving soil structure.
• Sub soiler — works at deep depths to break hard pans below the plough layer.
• Rotary plough — uses powered rotating blades for simultaneous cutting and mixing.

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List of Primary Tillage Implements

Country Plough (Indigenous Plough)

• Main parts of a plough:

  • Body — the main frame to which the shoe, beam and handle are attached.
  • Share — a narrow steel bar attached to the upper surface of the shoe longitudinally along the centre line. The share is the cutting element that penetrates the soil.
  • Shoe — the share is attached to the shoe which penetrates into the soil and breaks it open. The shoe also helps in stabilizing and balancing the plough while in operation.
  • Beam — connects the plough body to the yoke or hitch point.
  • Handle — allows the operator to guide and control the plough.

• The handle and beam are generally attached to the body of the plough.

• Types of shares:

  • Slip share
  • Slip nose
  • Shin
  • Bar point

• 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. This composition provides the hardness needed to resist soil abrasion while maintaining toughness to prevent breakage.

• The plough is provided with a wooden beam and a handle.

• Important points:

  • It is an animal drawn plough.
  • It penetrates into the soil and breaks it open. It forms V shaped furrows with 15-20 cm top width and 12-15 cm depth.
  • It can be used for ploughing in dry land, garden land and wetlands — making it a versatile tool for Indian farming conditions.
  • The size of the plough is represented by the width of the body and the field capacity is around 0.4 ha per day of 8 hours.
  • Working efficiency of desi plough is 0.32 hp/day.

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Sub Soiler

• All ploughs and Sub-soiler (opens up hard pan below 40 cm depth) are the primary tillage implements. Subsoiling is essential in fields where a compacted layer (hard pan) has formed below the normal ploughing depth, restricting root growth and water infiltration.

• Infiltration of soil with hard pan can be increased by subsoiling. Breaking the hard pan allows water to percolate deeper into the soil profile, improving moisture storage and root zone depth.

• Sub soiler works up to the depth of 45 - 75 cm. This is significantly deeper than conventional ploughing and requires high-powered tractors (typically 60 HP or above).

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Mould Board Plough

• Mould board is an implement which is used for ploughing. ^AFO-2021

• Mould Board ploughs are available for animals, power tiller and tractor operation, making them one of the most versatile primary tillage implements.

• While working, a mould board plough does four jobs namely:

  • Cutting the furrow slice — the share cuts the soil at the bottom.
  • Lifting the furrow slice — the mould board lifts the cut soil upward.
  • Inverting the furrow slice — the mould board turns the slice over, burying surface weeds and residues.
  • Pulverizing the furrow slices — the soil crumbles as it falls, breaking into smaller aggregates.

• Capacity 1.5-2.0 ha/day. The mould board plough is considered one of the most thorough primary tillage implements because it performs all four functions simultaneously.

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Disc Plough

• 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 a sliding plough bottom. The rolling action of the disc reduces soil adhesion compared to mould board ploughs.

• Disc plough is used for primary tillage and it is specially used where M.B. Plough is not useful such as hard and dry soil. It is also preferred in sticky soils, stony fields, and areas with heavy crop residues where mould board ploughs would clog.

• In some models, disc plough is designed to operate as 2, 3 or 4 bottoms, by adding or removing sub beams and sub beam assemblies according to requirement and available tractor power.

• Disc: It is a circular, revolving steel plate used for cutting and inverting the soil.

• Disc angle:

  • It is the angle at which the plane of the cutting edge of the disc is inclined to the direction of travel.
  • Usually the disc angle of a good plough varies between 42 to 45 degrees. A larger disc angle means the disc bites more aggressively into the soil.

• Width of cut of the plough increases by increasing disc angle. However, increasing the angle also increases draft requirement and tractor power needed.

• Tilt angle:

  • It is the angle at which the plane of the cutting edge of the disc is inclined to a vertical line.
  • The tilt angle varies from 15 degrees to 25 degrees for a good plough. The tilt angle controls how much the disc penetrates the soil — a greater tilt angle results in deeper penetration.

• Scraper: It is a device to remove the soil that tends to stick to the working surface of the disc. Scrapers are essential for maintaining the cutting efficiency of disc ploughs, especially in wet or sticky soils where adhesion is high.

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Secondary Tillage Implements

• Tillage operations performed after primary tillage to create proper soil tilth for seeding and planting are called secondary tillage. The goal is to refine the soil surface to the optimum condition for seed germination — fine, firm, and moist.

• These operations are lighter and finer operations performed on the soil after primary tillage operations. They require less power and work at shallower depths than primary tillage.

• Harrows, cultivators, sweeps, clod crushers, levelers, bund formers, puddlers, rollers and hoes are the implements that come under secondary tillage.

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Harrow

• A harrow is an 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 materials with soil.

• It is an implement used to break the clods after ploughing, to collect trash from the ploughed land and to level the seed bed. Harrows are the most commonly used secondary tillage implements.

• Harrow is used for harrowing, which is a secondary tillage operation that pulverizes, smoothens and packs the soil in seed bed preparation and to control weeds.

• Types of harrows used in India:

  • Disc harrow — uses rotating concave discs.
  • Spring tooth harrow — flexible teeth absorb shocks from stones.
  • Spike tooth harrow — rigid straight teeth for light leveling.
  • Blade harrow (Bakhar) — traditional Indian implement for shallow cultivation.
  • Triangular harrow
  • Zig-zag harrow
  • Bodela — region-specific traditional harrow.
  • Guntaka — traditional implement from southern India.
  • Bindha
  • Rotary tiller — powered implement for intensive pulverization.
  • Other harrows

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Disc Harrow

• It is a harrow which performs the harrowing operation by means of a set of rotating discs, each set being mounted on a common shaft.

• Disc harrow is found very suitable for hard ground with full of stalks and grasses. It can handle heavy trash conditions that would clog other types of harrows.

• It cuts the lumps of soil, clods and roots.

• Types of disc harrows:

  • Depending upon the source of power, disc harrows are of two types:
  • Tractor drawn (depending upon the disc arrangements, disc harrows are divided into two classes — Single action and Double disc).
  • Animal drawn

• Single action disc harrow: Harrow with two gangs placed end to end which throws the soil in opposite directions. A single pass leaves alternating ridges and furrows, so the field is not fully leveled.

• Double action disc harrow:

  • A disc harrow containing 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.
  • Thus the entire field is worked twice in each strip, resulting in a more level and finely tilled surface.
  • It may be of two types: Tandem and Off-set.

• Tandem Disc Harrow — has four gangs arranged symmetrically, providing balanced soil throwing in both directions for a level finish.

• Off-set Disc harrow — has two gangs arranged to one side, allowing the harrow to work under trees or close to fences where symmetrical harrows cannot reach.

• Parts of Disc Harrow:

  • Disc: Concave disc 35-70 cm diameter. The concave shape helps the disc scoop and turn the soil.
  • Gang: It is an assembly of concave discs mounted on a common shaft with spools in between.
  • Spool or Spacer: The flanged tube, mounted on the gang axle between every two discs to retain them at fixed position laterally on the shaft is called Spool or Spacer. It determines the spacing between discs.
  • The other parts are Gang bolt, Gang angle, Gang control lever, Spools or Spacer, Bearings, Transport wheels, Scraper and Weight Box.

• Tractor drawn harrow has a capacity of 2.5 ha/day.

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Power harrow — tractor drawn

• A power harrow tills the soil maintaining the same profile of the field. Unlike disc harrows, it does not disturb the vertical arrangement of soil layers.

• It pulverizes the upper and lower layer of soil without turning them upside down and thus it forms a good seed bed as well as good soil mulch. This is particularly beneficial for conserving soil structure and maintaining the natural layering of organic matter.

• It consists of two horizontal cross bars fitted with rigid pegs which reciprocate taking power from the PTO of a tractor.

• The pegs are spaced 200 mm wide and are staggered with respect to each cross bar. Staggering ensures complete coverage of the working width with no gaps.

• The two bars move in opposite directions and hence the implement is dynamically balanced. This means less vibration is transmitted to the tractor, providing a smoother operation.

• The oscillating pegs break the clods and pulverize the soil to a fine tilth.

• The width of the operation is 2000 mm and the field capacity is around 1.5 ha/day.

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Rotary Tiller (Rotavator)

• The rotary tiller or rotary cultivator is widely considered as the most important implement as it provides a fine degree of soil pulverization. It combines multiple tillage operations (cutting, mixing, leveling) in a single pass, saving time, fuel, and labour.

• It is directly mounted to the tractor and operated through the PTO shaft.

• The rotor is operated at 180-200 rpm.

• Capacity is 0.5 ha/hr.

• Types of blades used in rotary tillers:

  • ‘L’ type blade: Works well in trashy conditions. More effective in cutting weeds but does not pulverize the soil much. Suitable for initial land preparation where residue incorporation is needed.
  • Twisted blade: Suitable for deep tillage in relatively clean grounds, but clogging and wrapping of trash on the tynes and shafts needs frequent cleaning.
  • Straight blade: Employed on mulchers designed mainly for secondary tillage. Best for clean, well-prepared fields.

• The benefits of the rotary tiller are:
  • Effective pulverization of soil ensures good plant growth
  • Cutting and mixing of stubbles and roots and mixing with soil
  • Leveling of the field — all achieved in a single pass, saving time, fuel, and labour.

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Other Important Implements

• Basin lister: Used to prevent runoff and form basins in the field. Basins capture rainwater and allow it to infiltrate the soil, improving moisture conservation in dryland farming. This is particularly important in arid and semi-arid regions.

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• Sweep cultivator: Used for harvesting groundnut and in stubble mulching. The wide, flat sweeps cut below the soil surface, lifting groundnut pods or cutting weed roots while leaving surface residue intact for soil protection.

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• Potato digger: Used to harvest potatoes. It digs under the potato rows, lifting the tubers to the soil surface for manual collection. This significantly reduces the damage to tubers compared to hand digging.

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• Groundnut digger: Used to harvest groundnut. Similar in principle to the potato digger, it lifts the groundnut plants along with their pods from the soil.

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• Maize Sheller: Used to separate maize grains from cobs. It can be manually operated or power-driven, significantly reducing the labour and time required for hand shelling.

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• Seed dressing drum: Used to treat the seed with chemicals. The drum rotates and tumbles the seeds with fungicide or insecticide powder, ensuring uniform coating for protection against soil-borne diseases and pests. Proper seed treatment is one of the most cost-effective plant protection measures.

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• Hand gin: Used to separate lint from seed cotton. Hand gins are simple machines that pull cotton fibers away from the seeds, a process essential in cotton processing before the lint can be spun into yarn.

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• No-till planter: Used for sowing directly into unploughed soil. ^{AFO 2017} No-till planters cut through crop residue and place seeds into the soil without prior tillage, promoting conservation agriculture by reducing soil disturbance, conserving moisture, and lowering fuel costs. This practice also helps sequester carbon in the soil and reduce greenhouse gas emissions.

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Summary Cheat Sheet