April 21, 2014 — High-quality, and often expensive, seed can be planted at lower populations if you have the correct equipment for the task. A well-maintained and calibrated drill can improve your stands and increase yields while lowering your seed costs.

The seeding chart on your grain drill is a good start to determine seeding rate but may be significantly off target due to variations in seed size within species as well as wear and tear of the drill. So it makes sense to check the seeding rate. You can unhook some seed tubes and tie a small bag or cup to them and run a certain distance with the drill. The chart below helps you to calibrate the drill. The measures make sure that you collect seed for 100th of an acre so that you can just multiply the weight of the collected seed by 100 to get the seeding rate in pounds per acre. By using 100th of an acre you avoid large errors due to starting and stopping the drill.

Distance to drive to collect seed for 100th of an acre


  Number of openers used to collect seed
Row Spacing 3 openers 5 openers
7.5" 230 feet 140 feet
5.5" 317 feet 190 feet

Another way is to weigh out seed for, say, 2 to 5 acres (depending on desired seeding rate) and put it in the drill. Then you drill 1 acre or 4 (less than what you put in the drill to avoid running low on seed in part of the drill). You use the acre meter on your drill to know how many acres you planted. You can then vacuum out the seed that is left with a shop vac and weigh how much seed was left in the drill. The seed you drilled is the difference between the weight of the seed you put in the drill and the seed that is left over. Divide this by the area drilled to get the seeding rate.

A more detailed guide to seed drill calibration can be found in the fact sheet: Agronomy Facts #75 “Calibration Of Grain/Seed Drills".