Two dozen tractors rolled into East Thetford, Vermont, last month, carrying angry farmers, riled up about “freeloaders,” corporate influence, and what they see as an insidious threat to their livelihoods.

That’s because for decades, farmers have grown fruits and vegetables organically, relying on methods that replenish the soil. Thousands of them have gone through the rigorous process of earning the U.S. Department of Agriculture’s organic seal—a process they believe involves growing produce in healthy, biologically active dirt. To them, soil is a living thing requiring special care—an almost spiritual matter.

But in recent years, they say, the value of that process has eroded as produce grown through "soilless" farming, including hydroponics, has earned the organic label.

This week, they're hoping to settle a