Native Warm Season Grass Drill Calibration
Wheel Circumference Method
Measured Course Method

It is very important to calibrate your drill before planting. If you do not calibrate the native grass drill you may run out of seed or may have seed planted so sparse that it does not establish properly. Another issue is that if you run out of seed you probably will not be able to get it in time to finish seeding the field. When calibrating the drill you are calibrating it based on the bulk seed the you ordered based on the Pure Live Seed rate that was recommended.

Wheel Circumference Method

You can use the wheel circumference calibration method to get the drill set close to your desired rate. This method reduces the need to initially measure out a course and then have to move the equipment to run calibrations. By using this method you can have all of your tools close by in order to make any major adjustments that may be needed before you move out into the field. If you only use the wheel circumference method you should frequently check the bins and the amount of seed you have to determine if the seeding rate is too heavy. You can then adjust the rate lower in order to keep from running out of seed. To do this method you will need 4 bags or containers to collect seed in, screwdriver, jack, and scale that can measure the seed in grams.

1. Determine the amount of bulk seed that you have for the acres you plan to plant (see seed back labels).

Bulk weight ÷ Acres = __________lbs/ acre to plant

2. Calculate the planting distance of the drill and determine the number of row seed tubs on the drill for the seed box you will be using.

3. Calculate the circumference of the wheel. To get the diamete, measure from the outside of the tire on the left to the outside of the tire on the right of the axle.

(Diameter) X 3.14 = circumference

4. Use the following formula to calculate Square feet planted per 10 revolutions.

(Planting Width of Drill (ft) ÷ Number of tubes on drill) × 3 × (Tire Circumference × 10 Revolutions) = Sq. Ft. planted per 10 revolutions

The 3 in the formula is the number of tubes seed will be collected from.

After multiplying the tire circumference by 10 convert to feet instead of inches.

(______________ in. ÷ 12) = __________ feet
(_________________ ft ÷ ______________) × 3 × (______________ ft × 10) = __________ Sq. Ft planted per 10 revolutions

5. Engage the drive wheel of the drill.

6. Jack up the drill on the drive wheel side so that the wheel spins freely.

7. Remove the tubes from the bottom of the bin and attached the bags or containers you plan to collect the seed in.

8. Place seed in the bin over the 3 tubes you removed. Do not place it over any other opens as that seed will be lost to the ground.

9. Place a mark on the wheel or reference the location of the valve steam on the drive wheel.

10. Rotate the drive will 10 revolutions.

11. Place the empty bag on the scale and zero out the scale. Remove the 3 seed bags from the bottom of the bin and record the grams of seed.

12. Calculate the ounces of seed deposited per ten revolutions

____ grams ÷ 28.3 grams = ______ oz of seed planted per ten revolutions Drill Setting:_____

13. Now using the oz of seed per 10revolutions and square feet planted per 10 revolutions calculate the oz planted per acre

_____oz x 43,560 sq ft ÷ ______sq feet planted = _____oz planted in 1 acre.

14. Next calculate lbs/acre planted

______oz planted in acre ÷ 16 oz = ______ lb /ac planted

15. Reattach the bags or containers to the 3 tubes and run steps 10 through 14 2 more times before making adjustments to the drill settings.

16. Run steps 10 through 14 2 times for each drill setting. It is probably highly unlikely that your seeding rate will come out exactly as that calculated in step 1. Your best bet is to calibrate the drill so that it is one to three pound under. This way you can always go back over areas and should not run out of seed.

Top of Page

Measured Course Method

This method allows you to fine tune the drill calibrations based on terrain and speed.

Weigh the seed metered out for a fraction of an acre and then calculate the rate per acre. The following procedure is based on 1 /50th of an acre. Use this method when pulling drill to calibrate. To do this method you will need 6 bags or containers to collect seed in, screwdriver, 100 ft tape or measuring wheel, and scale that can measure the seed in ounces.

1. Determine the amount of bulk seed that you have for the acres you plan to plant (see seed back labels).

Bulk weight ÷ Acres = __________lbs/ acre to plant

2. Determine the row spacing of the drill. Measure the distance between packing wheels or cutler.

3. Use the table below to determine the distance the drill needs to be pulled in order to get 1/50th of an acre.

Row Spacing

Calibration Distance for

6 inches

290 feet

7 inches

249 feet

8 inches

218 feet

9 inches

194 feet

4. Mark out course distance based on above Calibration Distance.

5. Randomly select six seed tubes to attach containers or bags to for collection of seed.

6. Place a quantity of seed in the bin over the 6 seed tubes you plan to collect seed from with bags.; engage the drill and pull until the seed is flowing uniformly from the drill. Pull drill the specified distance required at a uniform speed.

7. Collect the seed metered out in the containers.

8. Measure the seed from all 6 collections in ounces. (remember to zero out the scale with an empty bag or container.)

9. Calculate the seeding rate using the following formula:

weight of seed collected (in ounces) X 50 /16= pounds per acre

10. Adjust seeding rate and repeat steps until the desired rate is achieved.

Top of Page

  What to do when

Use the planning calendar below for tips on enhancing your land throughout the year. Click any of the selections below for more details.