An attendee passes in front of John Deere brand tractors displayed during the World Agriculture Expo in Tulare, California, on Tuesday, Feb. 12, 2019.

The state of American agriculture is "rapidly deteriorating" into crisis, J.P. Morgan said Tuesday, due to three factors: declining exports, a poor crop of corn and soybeans and the trade war with China.

"Overall, this is a perfect storm for US farmers," J.P. Morgan analyst Ann Duignan said in a note to investors.

The most pressing issue facing farmers is that global agricultural markets are oversupplied, and that's putting "increasing pressure" on U.S. agriculture exports, Duignan said. A Department of Agriculture report last week "portrayed a grim outlook for US farmers" in that regard, she said.

"As a result of tariffs and excess global supply, US soybean export inspections are down 27%" year over year, Duignan said. She added that, at the same time, South America is having a banner year for production so "the export market is growing ever more competitive.

On China specifically, Duignan pointed to an outbreak of African swine fever in its hog herd as likely to cause a significant decline in "Chinese import demand for soybeans." The fever reduced about 30% of China's hog herd, according to J.P. Morgan. A decline in China's import of soybeans would be in addition to the tariffs already placed on U.S. exports of the crop, which has historically been the biggest American agricultural export to China.

Domestically, "the Midwest is off to a very slow start in 2019/20," Duignan said. The planting season is "off to a bad start," and corn and soybean crops are far behind in "planting progress" compared with last year, she said.