Corn producers should not promise in writing that the seed they plant is not genetically modified or "non-GMO."

That word of caution is from Denise McWilliams, agronomist with the University of Minnesota Extension Service.

No standards exist that require seed that is not genetically modified to be tagged as non-GMO seed, says McWilliams. The American Seed Trade Association has asked USDA to establish a standard. It suggests a one-percent maximum allowance of GMO seeds in a bag tagged "non-GMO." This would equal 800 seeds in a bag of corn with 80,000 seeds, or about 1,500 soybean seeds in a 50-pound bag of average soybeans.

"This standard is obtainable, and is higher than the standard for certified seed," says McWilliams.

Assuring non-GMO grain is now a complex operation, McWilliams points out. That’s especially true for corn, since it’s a cross-pollinated crop. "Farmers wishing to sell grain as non-GMO might consider testing their seed before planting," she says. "In addition, they may want to test the grain in the fall to insure a paper trail proving purity."