Bulk vs. Pure Live Seed (PLS)
All seed suppliers are required to include certain information on the tag relative to the quality of the seed. Two of the most important items are the purity (or percent of pure seed) and the percent germination.
How To Calculate PLS
(PURITY x PERCENT TOTAL GERMINATION) / 100 = % PLS
Percent Total Germination =
[Germination + Hard seed + Dormant]
(90 x [78 + 10 + 2]) / 100 = 81% PLS
A seed label indicates 90% purity, 78% germination, 10% hard seed and 2% dormancy. See formula calculated above.
How to Determine How Much Seed to Plant
Divide 100 by the percentage PLS (In the example above, it’s 81).
(100 / 81) = 1.2 pounds of seed
Therefore, 1.2 pounds of seed with a 90% purity and 90% total germination would be needed for each pound specified in the desired seed mix.
A less expensive mix with lower purity and percent germination might require much more bulk seed to compensate for the lower PLS percentage.
At Ernst Seeds, our seeding rates are based on bulk seed unless otherwise indicated.