Find guidance on how to calibrate grain drills and air seeders to maximize yield and economic return.
Operating planting equipment
The double disc press wheel drill used by many growers provides the best stands when traveling less than 4 miles per hour and seeding less than 2 inches deep in a firm seedbed at the optimal moisture level. Faster speeds may cause extreme variations in seeding depth.
Many air seeders and reduced tillage drills are designed to seed into high-residue conditions. Seeding unit design usually dictates seedbed preparation and pre-planting tillage needs.
Check seeding unit settings and seed placement performance in each field. As seedbeds dry, frequently check performance.
It’s essential to pack soil over and around seed for uniform emergence. This becomes critical for rough, cloddy, rapidly drying seedbeds and delayed planting. Reduced ground speeds enhance uniform seed covering and packing consistency.
Grain drill calibration
The seeding rate tables found in your operator’s manual or on the drill hopper cover are based on a standard weight per bushel for various crops. Wheat has a standard weight of 60 pounds per bushel.
Due to differences in varieties and seed lots, the seed size and weight may vary from the standard.
Seed metering systems are based on volume displacement. This means that, if one lot of seed varies in size and weight from another, the system will meter two different amounts of seed if you don’t change the drill setting.
For this reason, calibrate the metering systems for a seed size to plant a particular population per acre.
To check calibration for gravity drop disc drills, count the number of seeds dropped in a square foot or linear foot of drill row. Here’s a simple way to do this:
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Operate your drill on a firm soil surface at your normal operating speed. A slow speed will drop more seed than a faster speed.
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Count the seeds dropped in one foot of drill row.
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Multiply the single row seed count by the following drill row adjustment factor in Table 1.
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Make several counts and compare the seeds counted with the values found in Table 1. Note: The values listed in the table do not allow for reduced germination.
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Make adjustments if necessary and repeat your calibration.
| Row spacing | Adjustment factor |
|---|---|
| 6 inches | 2.0 |
| 7 inches | 1.7 |
| 8 inches | 1.5 |
| 10 inches | 1.2 |
| 12 inches | 1.0 |
The most accurate method of determining seeding rate is to collect the seed metered from your drill over a measured distance.
Here are the steps to do this:
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Measure out a distance for your drill width to equal to one-tenth of an acre. This distance is listed in Table 2.
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Place bags under all drop tubes or place a tarp under a parked drill.
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Operate the drill through the measured distance in the field at your normal operating speed. Or, if you prefer to do a stationary calibration, lift up the drill meter drive wheel, calculate the number of revolutions to cover one-tenth of an acre, engage the drill metering system and turn the drive wheel the number of revolutions equal to one-tenth of an acre for your drill width. To calculate the number of revolutions for your drill drive wheel, multiply the diameter of the drive wheel in inches times 3.14. This gives the distance around (circumference) your drive wheel in inches. Divide this number by 12 to get the circumference in feet. Example: 21-inch drive wheel x 3.14 = 65.9 inches; 65.9 / 12 = 5.5 feet.
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Weigh the seed collected and multiply the weight by 10 as the amount collected was from one-tenth of an acre.
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Compare this amount with the desired seeding rate. Make adjustments, if necessary, and repeat the calibration.
Note: You can also use this procedure to check the calibration of fertilizer applicators.
Table 2: Distance to complete one-tenth of an acre for different drill widths
| Drill width | Distance |
|---|---|
| 6 ft. | 726 ft. |
| 7 ft. | 622 ft. |
| 8 ft. | 544 ft. |
| 9 ft. | 484 ft. |
| 10 ft. | 435 ft. |
| 11 ft. | 396 ft. |
| 12 ft. | 363 ft. |
| 13 ft. | 335 ft |
| 14 ft. | 311 ft. |
Air seeder calibration
The air delivery system makes it difficult to collect seed at the openers with a tarp or in the bag.
These units usually have a catch box directly under the seed bin designed for calibration and a hand crank to measure out the seed over a particular distance. They’re usually designed to catch seed from one-tenth of an acre.
Follow the instructions in the operator’s manual for hand crank revolutions and make adjustments in the seeding rates.
Reviewed in 2018