Des Moines, Iowa — Ione Cleverley wasn’t eager to break up with her tenant, who had been farming 88 acres of her central Iowa land for more than a decade. He was affable and hardworking, but after harvesting his corn and soybeans, the farmer left her fields unplanted. Cleverley had learned that each spring, as the soil warmed and moistened, it released nitrogen—both naturally occurring and left over from the last application of synthetic fertilizer.
Rain washed the chemical into her stream, which flows into the Skunk River and thence into the Mississippi. Along its winding route, nitrogen, which converts to nitrate in water, presents two serious problems.
It threatens the health of those who drink it at the tap, and when it reaches the ocean, it hyper-charges the growth of algae and aquatic bacteria, which use up most of the oxygen in […]