Seed Drill Calibration in India: Calculate kg/ha and Check Every Row

A seed-rate lever position is a starting setting, not proof that a drill is delivering the intended kilograms per hectare. Calibration measures what the machine actually meters over a known equivalent area. For an Indian farmer preparing a sowing operation, the useful result is a repeatable record for this drill, this seed lot and this setup.

This guide covers the calculation and evidence to request for a conventional ground-wheel-driven drill. It is not a universal operating sequence for powered seeders, electronic planters or every zero-till machine. Use the particular implement manual and a trained operator for the physical test. Our examples are invented for arithmetic; none is a crop seed-rate recommendation.

Obtain the target before touching the setting

Write down the crop, variety, seed lot, planned row spacing and the locally recommended seed rate. Obtain the agronomic target from the applicable state agricultural university, KVK or qualified adviser, considering the actual sowing conditions. Clarify whether the recommendation refers to bulk seed mass or incorporates a viability adjustment. Do not compensate for uncertain germination by guessing a larger hopper setting.

The Mississippi State calibration guide explains why different seed lots and seed characteristics can change delivery even when a chart setting remains unchanged. We use that measurement principle, not its overseas forage rates as Indian crop recommendations. A previous season's successful setting is useful to record, but the new lot still needs verification.

Identify what drives the metering mechanism

TNAU's description of a seed-cum-fertilizer drill distinguishes the seed and fertilizer boxes, metering mechanisms, delivery tubes and drive wheel. It explains that changing the exposed fluted-roller length changes seed delivery. That describes a mechanism; it does not mean every drill's lever scale has the same relationship to output.

Record the drive arrangement, engaged rows and seed-meter setting. If fertilizer is also being applied, keep its target and calibration separate. A correct seed result does not establish fertilizer delivery, placement or compatibility. Have the operator identify the actual adjustment and test method in the implement manual before beginning.

Calculate the represented area correctly

For a uniformly spaced drill with all rows active and normal adjacent-pass spacing, working width is the number of rows multiplied by row spacing. Use metres. A hypothetical drill with 10 rows at 0.20 m spacing represents 2.0 m working width. The span between its two outer row centres is only 1.8 m; confusing that span with the full pass width changes the calculated rate.

Do not use tractor width, the hopper's outside dimension or transport width. If rows are blocked, spacing is irregular or the machine uses a bed layout, obtain the correct effective-width method for that configuration rather than forcing it into this simple example.

Eternal University's farm machinery practical manual, Exercise 13, provides the width-and-wheel-rotation approach to calibration. With working width W in metres, represented drive-wheel travel per revolution C in metres, and N counted revolutions:

Represented area, m² = W × C × N.

N is a count of revolutions, not a speed in revolutions per minute. Use the circumference or calibration factor specified for the test, and retain the method in the record. A stationary wheel test cannot by itself prove that field wheel behaviour will be identical.

Convert collected mass to kilograms per hectare

For seed collected from all active rows over the represented test area:

Seed rate, kg/ha = collected seed mass in kg × 10,000 ÷ represented area in m².

The factor 10,000 is the number of square metres in a hectare. Subtract the collection container's weight, keep seed and fertilizer samples separate, and do not combine kilograms with grams without conversion. If only some outlets were sampled, their represented width must match the sampled mass; using full drill width with a partial sample produces a false result.

A field-distance test uses working width multiplied by measured travel distance for the represented area. The actual collection arrangement must follow the manual. Nobody should walk beside moving outlets holding a bag or reach into an operating meter. Fit or remove collection equipment only with the machine safely secured and isolated as instructed.

A complete example, including the adjustment target

Assume solely for calculation that the approved test method uses the 10-row, 2.0 m drill above, a represented wheel travel of 2.0 m per revolution and 50 revolutions. Assume an agronomic target has independently been set at 100 kg/ha for this hypothetical case.

• Represented area: 2.0 × 2.0 × 50 = 200 m².
• Target collected seed: 100 × 200 ÷ 10,000 = 2.0 kg.
• Suppose the actual collected seed is 2.4 kg.
• Measured rate: 2.4 × 10,000 ÷ 200 = 120 kg/ha.
• The result is 20% above the assumed target.

The required output ratio is 100 ÷ 120, about 0.833 of the present output. That does not mean moving the lever by 16.7% will give the correct result: the adjustment may not be linear. Change the setting using the manual, repeat the same test and weigh again. Do not label the drill calibrated merely because the lever was moved in the expected direction.

A correct total can hide an incorrect row

Keep the individual outlet samples identifiable where the approved method permits. In the hypothetical test, equal delivery of the 2.0 kg target across 10 equal rows would average 200 g per row. Now imagine one row delivers nothing, another 400 g and the remaining eight deliver 200 g each. The total is still 2.0 kg, but the row pattern is plainly wrong.

This is a diagnostic example, not an acceptable variation limit. Investigate the affected outlet, tube or metering mechanism with power isolated; use the manufacturer's procedure or a technician. Obtain the applicable uniformity criterion rather than inventing a universal percentage tolerance. Repeat the check after the cause is addressed.

Verify in the field and keep the result reproducible

After the controlled test, confirm delivery and seed placement under representative field conditions following the manual. Check the required depth and row pattern as well as mass per area. A correct calibration total does not prove seed placement, germination or eventual yield. Do not apply a convenient generic wheel-slip correction without evidence for the test and field conditions.

Keep a record of the seed lot, target and its source, active rows, row spacing, width, wheel factor or measured distance, setting, collection mass, individual-row observations and repeat results. Also record the operator and date. Recheck after a relevant change such as a different seed lot, row arrangement or metering repair.

For planning how long the sowing operation takes, use the separate field-capacity worksheet. Kilograms per hectare answers how much seed is delivered; hectares per hour answers how fast the operation proceeds. Neither calculation should replace a check that the job is being done correctly.

Sources checked on 8 October 2026. The metric example and row-imbalance example are original Aglist calculations, not field-test results or prescribed seed rates.