BEIJING — As Brazil takes a greater share of Chinese soybean purchases away from American farmers, the U.S. is trying to win back buyers by emphasizing crop quality. "Soybean production in North America and soybean production in South America is very different," Carlos Salinas, executive director, East Asia, at the U.S. Soybean Export Council said in a presentation Tuesday at the China International Supply Chain Expo in Beijing. He compared a range of weather factors between a city in Brazil