Understanding Pure Live Seed (PLS)
The Pure Live Seed (PLS) standard was developed to aid in determining the appropriate amount of bulk seed to be applied.
PLS refers to the percentage of live seed by weight in a seed lot having the potential to develop into a seedling. Live seed refers to the germination percent, dormant seed and hard seed. The remaining seed in the lot contains inert matter, other crops and/or weed seeds and is not viable.
How to Calculate Total Germination and PLS
Percent Total Germination = (Germination + Hard Seed + Dormant Seed)
70 + 15 + 5 = 90% Total Germination
Use that figure and the purity percentage to calculate the PLS percentage.
Multiply Total Germination by Purity / 100 = PLS %
(95% X 90%)/100 = 85.5% of Pure Live Seed
What Does This Mean?
85.5% of this seed lot by weight has the potential to grow. If 10 pounds of pure live seed is needed on a site, the quantity of bulk seed needed is determined by:
- 100 / PLS = Pounds of bulk seed needed to produce 1 lb of PLS
- 100 / 85.5 = 1.16 lbs of bulk seed X 10 lbs = 11.6 lbs of bulk seed
- Pure Seed – Viable and non-viable seed of the desired species.
- % Purity – Percentage of pure seed by weight.
- % Germination – Percent of seed by weight having the potential to germinate relatively quickly.
- % Hard Seed – Percent of viable seed having a hard seed coat that can take longer to break and germinate.
- % Dormant Seed – Percent of viable seed taking longer to germinate, other than hard seed.
- % Total Germination – Percent of seed by weight composed of hard seed, dormant seed and germination percentage having the potential to produce a seedling.
- % Nonviable Seed – Percent of seed that will not germinate.
- % Inert Matter – Material other than seed.
- Viable Seed – Pure seed having the potential to produce a seedling.
- Weed Seed – Seeds or other reproductive parts of species recognized by law as weeds.
- Other Crop Seed – Seeds that are not weeds or pure seed.