Purity Test

A purity test separates pure seed, inert matter, other crop seed, and weed seed.

Purity: Expresses the composition of the seed lot and its degree of contamination by unwanted components. Purity + inert matter + weed seed + other crop seed must add up to 100 percent.

Inert Matter: Includes dirt, plant parts, and certain types of damaged seeds. Most grass seed should contain no more than 15 percent inert matter. Even low percentages of inert matter containing pieces of stem or unthreshed seed clusters can block passage through a drill.

Note: Purity and inert matter of grass, forb, and shrub seed will vary by species.

Other Crop Seeds: Seeds of species normally grown for crops that occur in amounts of 5 percent or less. If the types of other crop seed are a concern, you may request a complete seed analysis report for the lot, which lists other crop species and the number of seeds per pound of each crop.

Weed Seeds: Total amount of common and restricted weed seed found in the lot.

Note: The number of noxious weed seeds per pound is listed separately.

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Last Modified: 07/05/2007