DES MOINES, Iowa -- Aaron Lehman said he's seen his soybean prices drop by 20 percent in the past six months. And he’s not the only farmer feeling the squeeze.

​​​​​ "Like all farmers, we’ve been tightening our belts trying to make ends meet with low commodity prices and the one commodity that kind of hung in there for us was soybeans," said Lehman, president of the Iowa Farmers Union.

Farming and trade have become major campaign issues in Iowa as ranchers in the region deal with the growing fallout of the U.S.-China trade war.

Trade is now a central theme for 2020 Democratic presidential candidates in this key early-voting state that has the first say on who should win the nomination.

Concerns from voters come amid the on-going trade dispute between China and the United States that began last year after President Donald Trump imposed a 25 percent tariff on Chinese goods imported to the U.S.

Beijing responded by imposing a 25 percent tariff on American goods, including pork and soybeans, which has caused a strain in the pockets of farmers all across the country.

During a recent visit to Iowa, Julian Castro, former U.S Secretary for Housing and Development under the Obama administration, criticized Trump's foreign policies, including trade.

"Y’all are feeling the effects of this haphazard trade war that this president has created and some of these contracts that folks around here are losing may not come back," he stated to members of a grassroots organization in North Liberty, Iowa.

Iowa is the No. 1 pork producer in the country. The tariffs, hog farmers say, has had a major impact on the industry -- and it's unclear how long the trade war will last.

"With the tariffs that are going on, it’s been costing the producer about $8 a pig just from China tariffs, and they’re our biggest customer," said Randy Hilleman, a pork farmer from central Iowa.

TRUMP'S CHINA TALKS: EXPERTS SAY MORE NEEDS TO BE DONE TO PROTECT IP

President Trump has insisted that his strategy toward China is in the best interest of the farmers.

"We’re turning all of that around with fair trade deals that put American farmers, ranchers, and in fact put America first," he stated during the American Farm Bureau Federation's annual convention in New Orleans recently.

Yet the current trade dispute, if it goes unsolved, could cost Iowa farmers $800 million in total revenue through July of this year, according to a study conducted by Iowa State University.

There is concern a ripple effect could start to hurt other businesses.

CLICK HERE TO GET THE FOX NEWS APP

"There are a lot of people’s whose livelihood depends on farming. You know the trucking companies, or the processing plant, or even the stores that sells those goods," said Tim Hagle, a political science professor at the University of Iowa.

Farmers in Iowa said they are closely watching to see if the White House can strike a deal with China before a March 1 deadline by the president to raise tariffs.