text:  as long as he sees an economic return. It's a financial equation lots of food producers have to think about, because most of the time, farms operate on slim margins. Chad Zimmerman is the agri-food director at the non-profit BioSTL in St. Louis. He says there's still a gap between the new technology available and the farmers who put it to use, because many can't foot the bill to try something new on all their fields.