In the fall, I often receive questions about the appropriate settings for planting forages with grain drills. Frequently, the specific forage you wish to plant is not listed in the settings table on the grain drill. Planting at seeding rates lower than the recommended levels can result in sparse stands, which may lead to weeds that could impact forage yield. Conversely,exceeding the suggested seeding rate is not advisable, as it can lead to higher seed costs. Furthermore, as drilling equipment undergoes wear and components such as tires and cogs are replaced, the actual seeding rates may vary significantly from those indicated on the seeding charts associated with the drills. Below is a quick and easy method to calibrate your drill.
Please make sure the drill is properly functioning. Gather all of the supplies that will be needed to conduct the drill’s calibration and adjustment. These supplies include:
- Seed from the seed lot being planted
- An accurate scale capable of weighing in grams, preferably to the nearest 0.1 g.
- Calculator (optional, but recommended)
- Wire flags or turf paint to mark a distance
- Measuring wheel or 200-ft tape measure
- Collection containers (e.g., plastic storage bags or small cups)
- Cable ties and/or duct tape
- A tool kit including adjustable pliers, screwdrivers, a knife to cut cable ties or tape, etc.
Once these supplies have been gathered, set the seed metering units to the opening size specified in the owner’s manual or the chart on the underside of the lid on the hopper box (if available). If planting a species or mixture that is not specified in the manual/chart, use the setting specified for a seed that is of similar size as a starting point. Ensure that the seed cups are free of debris and set to meter seed. If they have been opened or are not set before seed is poured into the hopper box, one’s seed may flow out of the hopper box onto the ground. Fill the bottom of the hopper box that is to be calibrated so that each seed metering unit has at least 4 to 6 in. of seed covering the opening in the bottom. Engage the drill and drive forward for 100-200 ft to ensure that seed has filled the seed metering units and is being metered into the seed cups. It is crucial to start with seed metering units already primed with seed.
Step 1: For each of the metering units being evaluated, detach the drop tubes either from the drill’s metering unit below the hopper box or as it connects to the row unit. Ensure that all metering units and drop tubes are clean and clear of obstruction. Securely attach plastic baggies or cups to catch the seed either just below the seed cup/metering unit or at the bottom of the drop tubes (Figure 1).
Figure 1. Before beginning, assemble all the supplies that one will need. Plastic storage bags or cups can be used to catch the seed. If secured to the metering units with duct tape or cable ties, care must be taken to ensure that the drop tubes are free of obstructions by dropping a few seeds down the drop tubes to ensure that they drop through easily.
Step 2: Determine the width between row units by consulting the owner’s manual or measuring the distance between the center of one row unit to the center of the next row unit. Using this distance, determine the calibration distance from Table 1.
Table 1. Calibration distances for corresponding widths between row units on a no-till or conventional drill.
Step 3: Using wire flags, turf paint, or some other visible marker, measure and mark the calibration distance specified from Table 2 on the terrain that is typical of what will be planted.
Step 4: With the drill’s ground-driven drive mechanism engaged and traveling at the desired operating speed, start precisely at the beginning of the calibration distance and travel to the end of the calibration distance.
Step 5: At the end of the calibration distance and with the tractor and drill parked, collect the plastic bags or cups and record the weight of the seed in the collection devices (tare the scale to account for the weight of the bags/cups) using a scale that reads in grams.
Step 6: The grams of seed collected from traveling the calibration distance equals the pounds of seed being sown on a per-acre basis from that row unit. For example, if after traveling the specified distance, one collects 30 g of seed from one unit, then that row unit is metering the equivalent of 30 lb of seed/acre.
Step 7: Adjust the seed metering unit opening as needed and/or repeat to ensure that all row units are consistently metering a similar amount of seed (+/- 10% of the target rate).
This information is available in the publication, Preparing and Calibrating a No-Till or Conventional Drill for Establishing Forage or Cover Crops.
Below is two great videos on this subject.
If you have any questions please contact your local county Extension agent.