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Extension by Anowar Islam

by Wyoming Livestock Roundup

Calibration of your planter is essential to obtain accurate seeding rates; simply, planter calibration is setting seed output per unit area or distance traveled. Calibration of your planter can be accomplished by turning the drive wheel to estimate travel over a distance that is predetermined.
    There are several steps to follow for planter calibration, and following is the typical list of steps.
    1. Measure the circumference of the drive wheel that operates the seeding unit. For cultipacker seeders, the drive wheel is the roller.
    2. Take the drive wheel off the ground by lifting the machine. Attach calibration pans or bags to the outlet to collect the seed.
    3. Turn the drive wheel, counting the number of times to obtain a predetermined distance.
    4. Collect seed and take weight.
    5. Calculate the seeding rates (i.e., amount delivered per acre).
    To calculate the seeding rates, typically the following steps need to be followed:
    1. Calculate test area: test area = length of test run multiplied by the planter seeding width. The length is calculated by multiplying the drive wheel circumference by the number of turns that are counted.
    2. Calculate acreage: acreage can be calculated by dividing square feet of the test area by 43,560 square feet per acre.
    3. Calculate seeding rate: divide the seed weight in pounds by area in acres. This will result in the seeding rate (i.e., seed delivered) as pounds per acre.
    Below is an example of a drill, with the assumption that it has 10 seeding units, each seven inches apart on centers; drive wheel circumference is 8.5 feet; the driver wheel is turned 10 times, and the collected seed weight is two ounces. Therefore, the test area length is 85 feet (10 turns × 8.5 feet per turn); test area width is 70 inches, or 5.8 feet (10 seeding units × 7 inches); test area is 495 square feet (85 feet × 5.8 feet), or in acres is 0.0114 (495/43,560); seed weight in pound is 0.125 (2 ounces/16); thus the seeding rate is 0.125/0.0114 = 11 pounds per acre.
    The principles of the above example can be modified to determine seeding rates based on the planter and its operating systems. However, it is recommended to follow the manufacturer’s guideline to accurately calculate seeding rates.
    Anowar Islam is an assistant professor and the UW Extension Forage Agroecologist in the Department of Plant Sciences in the College of Agriculture and Natural Resources. He can be reached at 307-766-4151 or

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