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Commodities: Field Crops: Forages: FAQs

What is Pure Live Seed (PLS)?

Seed quality differs from lot to lot. Some lots may have lower germination rates or more inert material. Seeding rates are always listed on a pure live seed (PLS) basis. Thus, one should always ensure that the seeding rate being planted is correct by adjusting for differences in viable seed and purity. To adjust for these factors, calculate PLS for each seed lot by multiplying the percentage of viable seed (% germination) by the purity of the seed (% pure). For example, a seed lot that is 90% viable seed (% germination) and 90% pure would have 81% PLS (0.90 x 0.90 = 0.81).

Some seeds (for example, bahiagrass and switchgrass) have a substantial amount of dormant seed. Though this seed may be slow to germinate, it is still live and viable. When calculating PLS with seed lots containing dormant seed, the percentage that is dormant is included within the viable seed percentage (i.e., % germination + % dormant seed).