Types of Disc Harrows and Functional Design
A disc harrow consists of gangs of concave, circular steel discs mounted on a common gang axle, angled relative to the direction of tractor travel.
As the implement is pulled forward, the rotating discs slice through tough soil clods, incorporate fertilizer, and bury organic residue like paddy or cotton stalks into the seedbed.
- Trailed Offset Disc Harrow: Two gang rows angled in opposite directions; heavy-duty design for tough uncultivated land
- Mounted Tandem Disc Harrow: Four gang rows arranged in an X-configuration; attached directly via tractor 3-point linkage
- Disc variants: Scalloped (notched) front discs for cutting dense stubble paired with plain rear discs for fine pulverization
- Disc diameters: Standard disc diameters ranging from 18 inches (450 mm) to 24 inches (600 mm)
Tractor Horsepower Matching and Disc Capacity
Selecting the correct disc harrow size depends upon tractor engine horsepower, chassis weight, and soil texture.
Under-matching tractor horsepower leads to excessive wheel slippage, while over-matching can strain implement gang frames and bearing spools.
- 12 to 14 Disc Harrow: Matched to 35 HP to 45 HP utility tractors for small and medium landholdings
- 16 to 18 Disc Harrow: Matched to 45 HP to 55 HP tractors for intensive field preparation
- 20 to 24 Heavy Trailed Harrow: Paired with 60 HP and above heavy tractors for deep cultivation and commercial contracting
- Spool bearings: Heavy cast-iron bearing spools fitted with grease-sealed taper roller bearings
Commercial Price Variables and SMAM Subsidies
Commercial prices for disc harrows vary based on steel grade (high-carbon steel versus boron steel discs), gang frame box-section thickness, and brand reputation.
Under the Sub-Mission on Agricultural Mechanization (SMAM), eligible farmers can obtain capital subsidies of 40 to 50 percent on certified tractor disc harrows through state Direct Benefit Transfer (DBT) portals.
- Price determinants: Number of discs, disc diameter, boron steel durability, and hydraulic transport wheel inclusion
- Boron steel advantage: Boron alloy discs provide superior wear resistance compared to standard high-carbon steel
- SMAM Subsidy: Capital financial assistance for individual farmers and custom hiring centers
- Invoice requirement: Secure printed GST tax invoice with serial number and FMTTI test report for subsidy approval
Official source
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Common questions
What is the primary difference between a mounted and trailed disc harrow?
A mounted disc harrow connects directly to the tractor's 3-point linkage for easy hydraulic lifting, while a trailed harrow is pulled by the drawbar and supported on its own transport wheels.
Why are notched (scalloped) discs used on the front gang of a harrow?
Notched discs provide sharp cutting edges that easily slice through tough crop residues, roots, and hard clods, while smooth rear discs complete fine pulverization.
How much tractor horsepower is needed to operate a 16-disc harrow?
A 16-disc mounted or trailed harrow typically requires a tractor with 45 to 55 engine horsepower for smooth operation in normal agricultural soils.
General guidance, not personal advice. For your farm, ask your local Krishi Vigyan Kendra or agriculture officer.
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