KALONA, Iowa — This small town has become a landmark in the organic-farm movement, and it has nothing to do with foodies or hippies.

Instead it has been Amish farmers who, in their suspenders and wide-brimmed hats, have helped develop one of the densest clusters of organic farms in the United States. More than 90 operations certified by the Agriculture Department have emerged within a 10-mile radius, producing, among other things, corn, soybeans, eggs and, perhaps most important, milk.

“This is our living and our way of life,” said Eldon T. Miller, 71, an Amish dairy farmer here. A little over 20 years ago, Miller began holding informational meetings in his basement about organics, and the idea slowly spread across the area.

The question for small organic dairy farmers is how long they can hold out against growing competition from very big dairies producing large volumes of organic milk that, in the view of many here, does not deserve the label.

A glut of organic milk has sunk prices across the United States, threatening livelihoods and rekindling long-standing suspicions that some of the large organic dairies that have emerged are swamping the market with milk that does not meet organic standards. Over the years, some of these very large dairies, most of them in the West, have been cited for violating organic rules by the USDA or inspection agencies. To the chagrin of many here, most have been allowed to continue operating.