John Draper and I are sitting in the cab of a tractor on the research farm he manages for the University of Maryland, alongside the Chesapeake Bay. Behind us, there's a sprayer.
"So, away we go!" Draper says. He pushes a button, and we start to move. A fine mist emerges from nozzles on the arms of the sprayer.
We're spraying glyphosate, killing off this field's soil-saving "cover crop" of rye before planting soybeans.
Farmers have been using this chemical, often under the trade name Roundup, for about four decades now.