VIC, Spain — Rolling his rickety red tractor through a rural valley in Catalonia, Jordi Colom seemed like just another farmer heading to the fields. Except that he was in a line of dozens of tractors lumbering along. And cars honked in approval. People on the side of the road waved red-and-orange Catalan flags and cheered.

They knew the role played by the “tractorada,” loosely a tractor armada, in Catalonia’s continuing independence movement.

“Today, everyone wants to be a farmer,” said Imma Colom, 39, Mr. Colom’s sister, who was among the onlookers and whose husband was also driving a tractor.

In a region that draws part of its identity from the toughness of farmers, their tractors are now among the symbols of Catalonians’ fight for independence. In recent months, farmers have lent their strength to marches, riding slowly with the demonstrating masses. During the contentious referendum on independence, the tractors were positioned outside polling stations as a line of defense against intervention by the Spanish police.