Soybeans are the second-largest US crop after corn, covering about a quarter of American farmland. We grow more soybeans than any other country except Brazil. According to the US Department of Agriculture, more than 90 percent of the soybeans churned out on US farms each year are genetically engineered to withstand herbicides, nearly all of them involving one called Roundup. Organic production, by contrast, is marginal—it accounts for less than 1 percent of total American acreage devoted to soy.