The U.S.-China trade spat is cutting into the flow of soybeans, pork and other commodities from U.S. farms to one of the world’s biggest markets.

Since early April, when China announced tariffs on some U.S. agricultural goods and threatened to target others, Chinese importers have canceled purchases of corn and cut orders for pork while dramatically reducing new soybean purchases, according to U.S. Department of Agriculture data. Chinese importers’ new orders of sorghum, a grain used in animal feed, have dwindled while cancellations increased.

The chill in agricultural trade is sending jitters through the U.S. Farm Belt, which for years has dispatched farmers on trade missions to cultivate the Chinese market.

“As the summer persists and if nothing’s been resolved, it will start showing up as a pretty big hole in U.S. exports, ” said Soren Schroder, chief executive of Bunge Ltd., one of the world’s largest processors and traders of soybeans.

There is no specific date for the bulk of the tariffs China has threatened to impose, and senior U.S. officials including Treasury Secretary Steven Mnuchin and U.S. Trade Representative Robert Lighthizer are in Beijing this week for negotiations. Even if a deal is hammered out, the uncertainty created by threatened tariffs has been enough to curb deals in some of the most heavily traded products.