Perennial Ryegrass Seed Per Acre Calculator

The “number” (pure live seed, or PLS) is a factor in whether your lawn looks like sea of green or a checkerboard of bare spots, yet most folks has never heard of it. Here’s why: Your friend may purchase the same size bag of perennial ryegrass as you do, but while his seed boast 90 percent germination, yours is only 82 percent. So he’ll be getting more grass then you will.

Ryegrass spreads fast and are unforgiving of poor planning. Buy the correct amount with help of this calculator, which translates the numbers printed on tags to pounds of seed.

How to Calculate the Right Amount of Seed

The mistake most people (and many professionals) make when buying seed is assuming it’s all the same. The read they should of apply three hundred pounds per acre; so therefore I’ll apply three hundred pounds of whatever it was. Nope. Germination rates and purity rates is different numbers on the tag; the former multiplied by the latter equals the number of viable seeds in package. Ninety percent germination and ninety percent purity? Eighty-one percent viable seed. Divide your desired application rate by this number and you know how much seed in bulk you actualy need. People who skip this step is always going to be underseeded, particularly if they purchase old stock or commercial grade.

How much seed do you need? Seed requirements depends heavily on when it’s sown. If it goes down in that perfect early fall window, when soil temperature is between 50 and 65 degrees, then it get off to a fast start with little stress. But if you’re getting it down later in the season, as days grow shorter and the soil cools, there will be less time to get its roots down before the plant goes dormant. You’ll have to up your seeding rate according. The calculator accounts for this by adding a dormant- or late-fall-seeding multiplier. This adjust for slower germination and ensures enough seed survives through winter.

The other thing that has an impact as much as the timing is how you apply things. If you apply something by drilling or using a slit seeder, you are placing the seed right in the ground. This keeps them from being washed away or eaten by birds, and provides the moisture they need to grow. That’s more efficient (and thus you’ll need fewer seeds in all).

But if you are broadcasting seed around by hand or with a rotary spreader, the seed is sitting on the soil surface or on top of thatch, where wind and rain (and birds) has their way with them. If you pick the “broadcast” option when you set the tool, it will include a loss factor. It adjusts the number of seeds you enter by assuming that some won’t make it so you get an even stand anyway. It is a small detail, but it is important.

Now add in high-traffic areas like athletic fields. They gets foot traffic, balls, and cleats, but they also get a beating, which creates bare spots that require more aggressive repair. Often a new athletic field gets an even higher seed rate than your home lawn does, quickly creating a dense cover that can hold up to the physical stress. But when you’re overseeding a thinning lawn, the objective changes, you want to fill holes versus try to create a whole new canopy. Knowing the difference will prevent you from using a turf rate instead of a pasture rate, or vice versa. Doing so prevents wasted money and poor results.

The bottom line? A strong eco-system remains green throughout the year. And perennial ryegrass is indeed such a workhorse. But it’s also a creature whose biology has some math. When you get how all this plays out, how the time, the germination and the purity come together. You don’t guess anymore; you plan. You know exactly how many bags to grab from the shelf because the numbers now match what is actualy in your soil. And that makes the difference between a good lawn and a great one: confidence.