President Trump’s plan to impose a 100 percent tariff on Russian goods could raise the cost of urea, a key fertilizer in corn and other row crops.

American farmers are bracing for another blow should President Trump proceed with his plan to impose steep tariffs on goods imported from Russia, raising the price of a key ingredient in crop production.

The United States imported $1.3 billion worth of fertilizer — mostly in the form of urea and urea ammonium nitrate — from Russia last year and is on a pace to bring in even more this year. Farmers of row crops like corn and soybeans, the biggest users of fertilizer, are already dealing with low sales prices and cannot afford rising input costs or a slowdown in supply.

Mr. Trump threatened this week to levy a 100 percent tariff against Russia, as well as high tariffs against countries that do business with