Heisdorffer said farm income has fallen about 50 percent since 2013 and is forecast to decline another 6 and 7 percent this year. He said U.S. crop prices also have fallen significantly in recent years.
"We're going to end up with losing farmers," said Heisdorffer. "It's already close to happening out there now."
Earlier this month, Beijing warned it might impose a 25 percent tariff on U.S. soybeans as well as duties on other major U.S. agricultural products, including corn, wheat, cotton and beef. It followed the Trump administration threatening to slap tariffs on everything from Chinese consumer electronics and robotics to aerospace products.
"Retaliation is no longer a what if," said Heisdorffer.
Trump, in remarks during a meeting with governors and members of Congress, conceded that farmers "have been trending downward for a long period of time, and we're not going to have that. A lot of it is because of bad trade deals."
At the same time, the president insisted that "farmers are going to be — they're going to do fantastically well."
Besides farming soybeans, Heisdorffer also produces hogs — another agricultural commodity the Chinese have targeted.
Effective April 1, China slapped a 25 percent tariff on U.S. pork imports and a new 15 percent duty on other key agribusiness products, including apples, cherries, citrus and nuts such as almonds and pistachios. That retaliatory action followed Trump putting tariffs on imported steel and aluminum, citing national security concerns.
But Heisdorffer said trade with the world's second-largest economy has been a good thing for U.S. agriculture. He also said in testimony that trade actions threaten agricultural commodities and "have the potential to upend the farm and rural economy."
"We cannot afford to lose our valuable customer, China," the farm group leader said. "We have South America, who is more than anxious to take any of our trade that they can."
According to Heisdorffer, China imported 62 percent of total U.S. exports of soybeans last year and bought nearly one-third of the nation's annual soy production. Brazil is the world's top soybean exporter, including to China. Even so, value of U.S. soybean exports to China have jumped 26-fold since 1996, from $414 million to $14 billion last year.
Regardless, Trump said Thursday that "China has consistently treated the United States agriculture unfairly."
Heisdorffer said that for the last two decades the soybean industry has contributed more to the U.S. trade balance than any other agricultural product. He also said there is actually room for the U.S. soybean industry to grow its exports to China and added that the focus should be on finding "ways to expand trade rather than restricting it."
"We have more soybeans to sell; let us sell them to China," he said. "We've expanded that market over a number of years; it keeps growing. If we can continue to do that, it would put us in good shape."
Meantime, there were indications Thursday the Trump administration is looking at getting back into talks for the Trans-Pacific Partnership. A White House official confirmed the president's chief economic advisor, Larry Kudlow, and U.S. Trade Representative Robert Lighthizer will be looking into rejoining the TPP negotiations.
The American Farm Bureau Federation, the nation's largest agricultural trade group, hailed the development in a statement. "This is welcome news, especially for a farm sector that is experiencing the lowest income in 12 years," the group said. "We have long supported TPP — now known as the Comprehensive and Progressive Trans-Pacific Partnership — and hope the United States can soon join the 11 countries that have already signed on."
Within days of taking office, Trump announced the U.S. withdrawal from the TPP negotiations and agreement. Trump opposed the Asia-Pacific deal by contending it would hurt domestic manufacturers, but major agricultural groups supported it because it would have slashed tariffs on a wide range of U.S. goods over time, including food and farm products.