Calibration matters; a patchy lawn versus a uniform one often hinges on it. And most people don’t think of their spreaders as a mathematical tool, it’s a mystery, more or less, and they guess around with settings till they hit paydirt. It isn’t intuition so much as physics. To get the distribution correct, you must understand that different seed sizes requires certain opening widths (as chart above explains) to prevent either choking up or starving your soil.
Consider your spreader to be a delivery truck: Small packages (think Kentucky bluegrass seed) need only the tiniest crack opened up to let things flow out evenly; if you crank it way open to handle giant sacks of fertilizer, you’ll dump wall of seed in front of your feet. This is where visual guide shows the difference between rotary broadcast spreaders and drop spreader, because the latter is a more precise instrument for dropping seed right under the hopper. It’s better for filling out small area, and for edging along flower bed. With a rotary, a spinning disc sprays seed in a broad arc, covering large areas fast, but not as precisely along line of your property edges. Half the fight are picking the wrong weapon, before ever turning the dial.
How to Use Your Spreader Correctly
Mechanics aside, timing is key. For instance: Perfect calibration of your spreader doesn’t matter one bit if you seed cool-season stuff like Kentucky bluegrass too early on a chilly day in early spring. That’s just burning money. Cool-season types prefers to germinate at times when ground has held some summer heat, yet the air is starting to cool again. Therefore, late summer or early fall is prime time.
Warm-season species (such as Zoysia or Bermuda) want it hot: Heat triggers germination. The graphic up top points out the timing element, when they really need it. As a fact of biology. A cool-season seed will lie dormant in cold soil, waiting for warmer days to kick-start things. And meanwhile it’s sitting there, exposed to rot, ants, and birds. Knowing what sort of grass wants what kind of weather would of spared you a week of watching seed waste away in the dirt, doing nothing.
And then there’s the last obstacle: calibration. Many pros swear by tarp test as best way to go. You spread a plastic sheet out on your driveway. You fill up your hopper with a set amount of seed. Then walk at your regular seeder speed along its length. Scoop up all the seed you dropped, and weigh it. Compare it to recommended rate for that much area, and adjust your setting accordingly (close it down a notch or two if you’re dumping out too much; open it up a bit if you’re under-seeding). It is a simple experiment that takes away the guessing game.
It will account for differences among brands, and variations in seed moisture level, that generic charts can’t predict. Most folks move fast during the application stage. The key’s largely psychological: They’re anxious to apply the stuff and head back indoors. Slower means they cover evenly. Faster means gaps appear. Slower yet means clumping occur.
Walk briskly, but at a regular pace; maintain an even flow. Then walk across at right angles to those passes, applying half your seed in each direction. That cross-hatching covers any missed spots, and there will be some. It takes only another 10 or so minutes, but it ensures an even application. It is an extra step, but it is guaranteed.
And don’t skip the final step, which is cleaning your spreader. The mess of fertilizer mixed with leftover seed hardens like cement in the mechanism, and throws off next year’s calibration. Again: Rinse it out. Let dry. If there is exposed metal bits, oil them. You will not only extend life of the tool but also preserve its accuracy. Clean tools = calibrated tools. Time your application according to the seasons: Your lawn will thank you for taking the time.