Glyphosate, the active ingredient in Roundup weed killer, is the most widely use herbicide in the United States. The introduction of genetically modified “Roundup Ready” crops—which allow farmers to spray large amounts of the herbicide on their fields without killing the crops—in the mid-1990s dramatically increased its agricultural use, but another lesser known agricultural use of glyphosate is as a pre-harvest desiccant, or drying agent.