Thetford — A group of farmers, activists and lawmakers will rally to keep the certification of “organic” food rooted in soil-based farming.

The rally is coming a month before the National Organic Standards Board will debate whether to allow hydroponically-cultivated crops — crops grown primarily in water, instead of soil — under the organic standards.

A parade of 25 tractors will ride down the center of Thetford on Halloween weekend.

Participants in the rally, organized by the Northeast Organic Farming Association, will be trying to bring attention to the debate of whether or not hydroponic growing should be considered certifiably organic.

Sen. Patrick Leahy and Rep. Peter Welch are expected to join a large number of farmers who will say “no” at the event.

The National Organics Standards Board will be meeting in St. Louis next month to make their decision.