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Making an Informed Seed Purchase

Posted May 1, 2000

Knowledge is power. This adage can be applied to purchasing decisions, whether regarding buying a house, seed, or fencing wire. After you read this article, you should be able to make a "powerful" decision the next time you purchase seed.

The first, and probably most important, step is to decide which variety to purchase. Good sources of information include local extension personnel, seed company representatives, and Noble Research Institute specialists, as well as variety trial publications by OSU, Texas A&M, and the NF. It's also a good idea to visit with neighbors who have grown a variety that you are considering.

Incidentally, grass or legume varieties are sometimes marketed as VNS, or variety not stated. For example, the seed could be a varietal mixture, an unknown variety, or an old one that doesn't sell well. It's best to avoid VNS seed because there is little if any information on its performance.

Seed can be marketed as several classes, including foundation, registered, certified, and noncertified. The same classes also apply to bermudagrass sprigs. Foundation seed is used to establish fields, which in turn will produce certified or registered seed. Purity standards, and thus cost, are higher for foundation than certified seed. Certified seed is sold in bags with a blue tag that lists such things as the variety name; germination, weed seed, and inert matter percentage; seed lot number; and source of production. Certified seed must meet fairly strict purity requirements; in some states more than 1 percent each of other varieties' or crops' seed is unacceptable. On the other hand, the only purity requirement of noncertified seed is that it be free of noxious weed seed (e.g., field bindweed, musk thistle). Often noncertified seed will be marketed as 'Common', such as 'Oklahoma Common' alfalfa. As with VNS, it's best to avoid common seed and purchase certified seed. For instance, researchers at the University of Wisconsin tested fifty-seven different lots of common red clover seed in comparison with 'Arlington'. Even though Arlington was an older cultivar developed in the 1960s, it still produced higher forage yields than all the common strains over a three-year test period. In some cases certified seed will be unavailable. Almost all of the annual ryegrass produced and sold in the USA is noncertified because the cost of producing certified annual ryegrass is much higher. In such cases it is still wise to avoid common seed.

Seed can be sold as either bulk or pure live seed (PLS). The formula for figuring PLS is as follows: % PLS = 100 (% contamination + (100 - % germination)) Let's say you purchase 50 pounds of bulk seed that tests 8 percent inert matter, 1 percent weed seed, 1 percent other crop seed, and 98 percent germination. What would the PLS percentage be?

= 100 (8 + 1 + 1 + (100 98))
= 100 (10 + 2)
= 100 - 12
= 88%

How much germinable, pure seed would there be in a 50-pound bag?

Pounds PLS
= bulk pounds x % PLS
= 50 pounds bulk x 0.88
= 44 pounds PLS

In other words, of the 50 pounds you purchased, 4 pounds were inert matter such as chaff and dirt; 0.5 pound was weed seed; 0.5 pound was other crop seeds, say, wheat grains in a bag of alfalfa seed; and 1 pound failed to germinate, leaving you with 44 pounds of PLS. Which is the better buy, bulk seed at $0.95 per pound or PLS at $1.00 per pound?

PLS Cost
= bulk price/% PLS
= 0.95 / 0.88
= $1.08

In this example, purchasing seed as PLS ($1 per pound PLS) is less expensive than as bulk ($1.08 per pound PLS).

Seed that is dormant and capable of germinating but fails to do so in a standard germination test is called hard seed and is not included in the PLS percentage. Some legumes and native grasses can have a high percentage of hard seed and may require a wet chill treatment to reduce it. As a general rule, seed that has a high germination percentage will help reduce the incidence of poor stands.

The moral of the story is that purchasing seed can be an important part of your farming and ranching enterprise, so gather plenty of information beforehand. And good luck!