The agricultural woes in Wisconsin are a microcosm of the difficulties that farmers across the country have faced as a result of the multifront trade disputes that have lingered for more than a year. In 2018, farm income nationally was $63.1 billion, the second-lowest total in a decade. Commerce Department figures released on Friday suggested that farmers were not anticipating much relief, as purchases of agricultural equipment were tepid.

A report last year from the U.S. Dairy Export Council estimated that over the next several years, retaliatory tariffs by China and Mexico could cut American dairy exports by $2.7 billion and lower dairy farmers’ revenues by $16.6 billion if they were not rolled back.

“He’s talked over time about how much he cares about these dairy farmers, but he hasn’t really followed up with any certainty,” Senator Tammy Baldwin, Democrat of Wisconsin, said of Mr. Trump in an interview. “Our farmers need good trade deals, not trade wars.”

Representative Mike Gallagher, a Republican from the Wisconsin district that includes Green Bay, said he had urged the White House to roll back the steel and aluminum tariffs that Mr. Trump had imposed on Canada and Mexico so that farmers in his state could get relief. He said that the top concerns of dairy farmers were the tariffs, along with Mr. Trump’s immigration policies, which make finding farm labor more difficult.

“Wisconsin farmers are caught in the crossfire,” Mr. Gallagher said.

The financial strain proved too much for the Voelker family in Rice Lake, a town of fewer than 10,000 people in western Wisconsin. The Voelkers sold 20 milk cows this year and the remaining 40 are expected to be gone by September, as the farm transitions to producing grain and crops. Cows that used to sell for $2,000 each a few years ago are now worth only $800. The hope is that by getting out now, they can save a family farm purchased in 1940.