The signing of a renegotiated free-trade agreement between the U.S. and South Korea is spurring optimism that export markets for American farm goods won’t shut down and may even expand. President Donald Trump and his South Korean counterpart Moon Jae-in signed the agreement Monday on the sidelines of the United Nations General Assembly, the first major trade deal the U.S. president has forged amid rising trade tensions. It’s welcome news for U.S. farmers worried that the closing of export markets, especially China, will exacerbate the impact of low prices due to expanding supplies of corn, soybeans, beef, pork and chicken.South Korea is the sixth-largest export market for U.S. agriculture, buying $6.9 billion worth of farm goods last year, according to the American Farm Bureau Federation. The free-trade agreement with the two countries has helped make South Korea the second-largest importer of U.S. beef after Japan by sales. U.S. pork exports have also risen.