Last reviewed 1 Oct 2026 · 9 min read
Objectives of sowing equipment
A good sowing machine should: (1) place seed at the correct depth and spacing; (2) maintain the desired seed rate; (3) give uniform emergence with minimal seed damage; (4) cover the seed and press the soil; (5) handle different crops with small adjustments; (6) place fertiliser (in a combined machine) near but not touching the seed.
Methods of sowing
| Method | Description | Remarks |
|---|---|---|
| Broadcasting | Scattering seed by hand or a broadcaster over the surface, then covering by harrowing | Uneven depth and spacing, high seed rate; used for small-seeded crops, pastures |
| Drilling (line sowing) | Seeds dropped in continuous rows at a uniform depth by a seed drill | Good uniformity, seed saving, easy interculture; for wheat, gram, mustard, sorghum, millets |
| Planting (precision sowing) | Individual seeds at a fixed spacing within the row by a planter | Maize, cotton, sunflower, soybean, sugarcane setts; saves seed, easy thinning |
| Dibbling | Making holes and placing 1–3 seeds by hand or a dibbler | Small areas, high-value seeds |
| Transplanting | Raising seedlings in a nursery and planting them out | Rice, vegetables, tobacco; rice transplanters |
| Hill dropping, check-row planting | Seeds at corners of a grid | Cotton, maize (weeding in both directions) |
| Raised-bed and furrow planting | Seeds on beds with furrows between | Water saving, drainage |
| Zero-till (no-till) drilling | Direct sowing through the stubble | Wheat after paddy |
Seed drill — functional parts
- Seed box (hopper) — holds the seed; has a lid, agitator and partitions for different seed sizes; often a fertiliser box as well.
- Metering (feed) mechanism — meters the seed (volume per revolution) from the hopper to the tubes.
- Seed (delivery) tubes — flexible or rigid tubes (telescopic) carrying the seed from the metering unit to the furrow opener.
- Furrow openers — make a furrow of the required depth for the seed.
- Covering device (press wheels, drags, chains) — cover the seed and firm the soil around it.
- Frame, wheels, drive and clutch — the ground (drive) wheel turns the metering shaft; a clutch disengages it for transport.
- Depth and spacing adjustments; marker (for row alignment on the next pass).
Metering mechanisms
| Type | Principle | Used for |
|---|---|---|
| Fluted (grooved) roller (feed roll) | A roller with longitudinal flutes rotates in the hopper outlet; the flutes carry a volume of seed per turn; the seed rate is changed by the length of the roller exposed (feed-roll sliding) and by the speed | Cereals — wheat, barley, small seeds (the commonest drill meter); can damage large or fragile seeds |
| Cup (cell) feed | Cups on a belt or wheel pick up seed and release it into the tube | Maize, sorghum, beans, sunflower (precision) |
| Horizontal plate (cell plate) | A rotating plate with cells (holes) of a chosen size; a knock-out ejects each seed; often with a cut-off | Maize, cotton, sorghum, soybean planters |
| Inclined plate | A plate set at an angle with cells; seeds picked up from the bottom of the hopper and dropped at the top | Precision planters (cotton, maize, groundnut) — good singulation |
| Vacuum (air) metering | A disc with holes held under suction; seeds held by the vacuum and released when the vacuum is cut off | High-accuracy precision planters (maize, sunflower, vegetables) |
| Pressure (pneumatic) type | Air pressure pushes the seed into cells | Precision planting |
| Brush, belt, finger pick-up | Gentle singulation | Soybean, vegetables |
| Studded roller, picker wheel, star wheel | For sugar beet, potatoes | Specific crops |
| Gravity and centrifugal metering | Simple | Fertiliser spreaders, broadcasters |
Seed drop — mechanical vs pneumatic
- Mechanical metering is simple and cheap, but accuracy falls at high speeds and seeds can be damaged.
- Pneumatic (vacuum) planters give precision at 6–10 km/h and less skipping/doubling, but cost more and need air/vacuum sources (from a PTO fan).
Furrow openers
| Type | Description | Suitable for |
|---|---|---|
| Hoe (shoe) opener | A narrow, chisel-shaped tool that pushes the soil aside | General use; light soils with little trash |
| Shoe (runner) opener | A sled-like shoe pressing a furrow (a slightly curved) | Moist soil, uniform depth |
| Single disc opener | A tilted disc forming the furrow | Trashy fields, zero-till; light to medium soils |
| Double-disc opener | Two discs set at an angle forming a V furrow, with the seed dropped between them | Precision depth, moist soil; planters |
| Stub-runner, chisel-point opener | Strong narrow point with penetration | Hard soil, zero-till (inverted-T) |
| Winged / inverted-T openers | Create a slot with a band at the base for the seed with minimum soil disturbance | Zero-till drills (wheat after paddy) |
| Anchor (hoe) openers | Anchor-shaped | Heavy soils |
Covering and pressing devices
Drag chains, scrapers, covering discs, press wheels (V-type or rubber), and rollers cover the seed and press the soil over it for good seed–soil contact (capillary water movement); depth control gauge wheels keep the planting depth uniform.
Planters and special machines
Row-crop planter (precision planter)
A toolbar frame carrying several row units (hopper, meter, opener, press wheel, fertiliser attachment), set at the row spacing (45–90 cm for maize and cotton); seed spacing within the row set by sprocket changes (drive ratio) or cells. Mounted type for tractor power.
Zero-till drill
A tyne-type seed-cum-fertiliser drill with inverted-T (or double-disc) openers; sows wheat directly into the unploughed paddy stubble after cutting the rice residue (Happy Seeder), saving time, fuel, water and cost, and improving timeliness. Happy Seeder — a stubble-handling drill with flails that cut and spread the straw and sow in one pass.
Rice transplanters
- Walk-behind (2–4 row) and riding (6–8 row) self-propelled machines that plant mat-type seedlings (15–20 days old, raised on a mat nursery) at a spacing of about 30 × 12–18 cm; a fork picks 3–5 seedlings from the mat and pushes them into the puddled soil. Capacity: 0.2–0.4 ha/h; saves labour (about 25–30 days of labour per hectare by hand) and gives uniform spacing and depth.
- Direct seeded rice (DSR) drills — dry-seeded rice, a water- and labour-saving alternative.
Potato planter
Automatic (cup-type or finger-pick) planters meter whole or cut tubers (30–60 g) at about 20–30 cm spacing in ridges; combines furrow opening, fertiliser placement, planting, covering and ridging.
Sugarcane planter / cutter planter
Opens a furrow, cuts the cane into setts (2–3 buds) and drops them end-to-end, with fertiliser and chemical treatment; covers the setts. Capacity: 0.2–0.5 ha/h.
Vegetable and seedling transplanters
Semi-automatic transplanters for tomato, chilli, brinjal, cabbage — an operator feeds the seedling to a picker that plants it at the set spacing.
Broadcasters (spreaders)
Centrifugal spreaders (disc type, with PTO or ground drive) broadcast seed and fertiliser; the spread pattern depends on the disc speed, vane position and drop point.
Calibration and seed-rate calculation
Seed rate is the mass of seed sown per unit area (kg/ha). For a drill with rows spaced (m) apart, working width , calibrated by jacking up the machine (or by a short run on the ground), turning the ground wheel a measured number of revolutions, and weighing the seed delivered:
- Distance per wheel revolution ( = drive-wheel diameter, corrected for slip).
- Area covered per revolution .
- Seed delivered per revolution (g) from the test.
- Seed rate (g/ha), or to give kg/ha for in grams per m².
A 9-row drill with a row spacing of 22 cm ( m) has a drive wheel of diameter 0.50 m. The ground wheel is turned 20 revolutions with the machine jacked up (distance m); the seed collected is 650 g. A slip allowance is ignored for the test.
Area covered . Seed rate — a little higher than the usual wheat rate of 100 kg/ha, so the feed-roll length is slightly reduced and the test repeated. (In the field, wheel slip of 5–10 % shortens the distance, so the actual rate is higher; the calibration is done on the ground when high accuracy is needed.)
Row spacing, plant population and seed rate
- Plant population .
Field performance and operating factors
- Ground speed: 3–6 km/h for conventional drills; precision planters up to 8–10 km/h with pneumatic meters; high speeds bounce seed and cause spacing errors.
- Seed depth must suit the crop (wheat 4–6 cm, maize 5 cm, cotton 3–5 cm, mustard 2–3 cm, soybean 3–4 cm); a firm, moist, level seed-bed gives uniform germination.
- Field capacity ha/h (field efficiency 60–75 %).
- Seed damage — keep below 1 %; avoid dropping from a height, sharp feed rollers or tight clearances; seed treatment (fungicide) should not clog the meters.
- Fertiliser placement — a separate tube to a band 3–5 cm to the side and below the seed (to avoid fertiliser burn).
Frequently tested points
- Methods: broadcasting, drilling, planting (precision), dibbling, transplanting.
- Parts of a seed drill: hopper, metering device, seed tubes, furrow openers, covering device, ground wheel and clutch.
- Meters: fluted roller (cereals), cup/plate (maize, cotton), inclined plate, vacuum (precision).
- Openers: hoe, shoe, single and double disc, inverted-T (zero-till).
- Seed rate from calibration; plant population from row and plant spacing.
- Zero-till drill and Happy Seeder for wheat after paddy.
- Setting the drill at a high speed (seed bounces, spacing errors).
- Using a fluted-roller drill for large, fragile seeds (damage).
- Placing fertiliser in contact with the seed (burn).
- Sowing methods range from broadcasting to precision planting and transplanting; row sowing gives better uniformity.
- A drill has a hopper, a meter, tubes, openers and covering devices; the meter type depends on the seed.
- Opener choice depends on soil and residue; inverted-T and disc openers suit zero-till.
- Calibration fixes the seed rate; plant population follows row and plant spacing.
- Special machines — transplanters, potato and sugarcane planters — handle other crops.