Seed purity is a crucial component for high yields
When buying seed, yield potential, disease resistance and stress tolerance are top of mind. Seed companies also add seed purity to that list. Although it’s not a big concern for farmers because U.S. law dictates that genetic purity has to be 95% or higher, seed companies are diligent.
"As seedsmen, one of the things we attest to is the delivery of the most pure product that we can without mixtures from other varieties or hybrids," says Terry Dulaney, CEO of Dulaney Seed and southeastern regional vice president of the American Seed Trade Association.
Pure genetics encourage the crop to get off to as good a start as possible, which carries through to season’s end with higher yields and profits.
"Research repeatedly shows that purity and high germ standards will outperform crops that are mixtures or crops that have lower vigor," Dulaney explains. "For example, just 2% better germination on corn seed results in another 640 plants per acre, which translates to approximately 5 bu. more per acre."
What’s in the bag. Michael Stahr, program manager at Iowa State University’s (ISU) Seed Testing Laboratory, breaks down seed purity into two types: genetic and mechanical. Genetic purity of seeds refers to the trueness to type. Mechanical purity takes into consideration how much of a seed lot is the species or crop it’s supposed to be and how much is weed seed, inert matter and other crops.
"The variety or cultivar purity is absolutely critical," Stahr says. "When you want a particular seed variety to plant, regardless of crop, you’re buying it to gain particular agronomic traits. Whether it’s stand, yield or any other factor, you have to know you’re getting precisely what you need—and therefore the purity is vital."
Stahr makes it clear that mechanical purity is also of tremendous importance. No farmer can afford to plant weed seeds or crops other than what’s intended. Weed seeds, common and especially noxious, are a big concern. Noxious weeds spread with ease, and in most states, if a primary noxious weed seed is present in the mix, the seed lot can’t be sold.
When Stahr conducts a mechanical purity test, he reports back to the given seed company and details which common weeds are in the lot, but that data doesn’t go on the label. However, when noxious weeds are in the mix that information does get included on the label.
Stahr’s laboratory tests more than 300 seed species, primarily corn and soybeans. But regardless of the crop, if it grows from a seed, Stahr has probably tested it at one time or another.
Pass the test. "Large seed companies do their own testing, but use us as a reference lab," he says. "Smaller seed companies, in accordance with U.S. law, need external seed labs to do testing if they don’t have a registered seed technologist on staff."
Seed companies send samples and can request a host of different tests; the ISU lab offers approximately 50 tests. The time it takes to run a test varies by the type of test to be performed and the crop. For example, a germination test on cotton takes 10 days. For corn and soybeans, results only take a week.
The agriculture industry can’t afford to cut corners in regard to purity. As technology continues to advance, the importance of seed purity will grow.
"A farmer must know what they’re getting," Stahr says