Use extreme caution when signing contracts regarding the genetic content of crops, warns Kent Thiesse, an educator with the University of Minnesota Extension Service.

"Producers need to be very cautious about signing any type of non-GMO certification or contract with a grain dealer or processor," says Thiesse. "Otherwise, producers may be responsible for meeting criteria that are beyond their control."

Growers can reasonably state that they have planted seed represented by the seed company as non-GMO or that they haven't planted seed represented as GMO. In addition, Thiesse says growers can state they've been careful to avoid contamination in harvest, storage and transportation.

However, don't sign a certification that states your grain has no GMO germplasm or that it wasn't contaminated in harvest, storage or transportation. Also, beware of certifications requiring you to claim no contamination occurred from pollen drift.

"Producers should not sign documents that may leave them liable for practices over which they have no control or that occurred after the grain left the farm," Thiesse says. "If they are in doubt, they need to seek the advice of an attorney or legal professional."