Deb McKee Kelly of Good Life Farms drove to the Bloomington Winter Farmers Market from Eminence, Indiana with 120 heads of lettuce.

She's planning to sell them all this morning.

She and her husband Darin use a hydroponic system to grow lettuce, arugula and basil in heated greenhouses. They made the switch to growing without soil four years ago, and their efficiency and productivity skyrocketed.

Kelly explains hydroponic growing in simple terms. "It's just growing with the roots suspended in water that's infused with nutrients from mineral salts," she says.

While she's confident she'll return to the farm empty handed, Kelly says it wouldn't be a problem if she had unsold heads of lettuce once the market closed.

"The nice thing about our hydroponic set up is if it doesn't sell, I can take it back. The roots are still there, so I can put it right back in the system and let it grow for another week," she says.