Nitrate from fertilizer and manure befouls countless waterways and kitchen taps across the US. But unlike other big polluters, from petroleum to plastics, Big Agriculture has largely avoided responsibility for its dirty footprint. In no state is this arguably clearer than Iowa, where the multibillion-dollar corn industrial complex of farmers, food processors, tractor makers, chemical companies, ethanol producers and their lobbyists reigns supreme.
 
来自肥料和粪便的硝酸盐污染了美国无数的水道和厨房水龙头。但与石油、塑料等其他大污染源不同,大农业在很大程度上避免了对其污染足迹负责。没有哪个州比爱荷华州更能清楚地展示这一点,这里是数十亿美元玉米产业复杂体的中心,包括农民、食品加工商、拖拉机制造商、化学公司、乙醇生产商及其游说者的主场。