The caucuses are over and aspiring Republican presidents are gone. Behind them, they leave what are politely known as anaerobic lagoons - giant stinking lakes of sewage from huge indoor pig-rearing plants which have been the real controversy in the state these past 12 months.
In recent years, vast "hog confinement units" have become a staple of the Iowa landscape, long structures containing thousands, sometimes tens of thousands of animals. Nature being what it is, however, pigs (or hogs as they are known in these parts) produce waste, a grown one more than an adult human. So where to put the stuff?
The answer has been the manure lagoons, vast holding ponds of excrement, lined with clay and producing odours across the neighbouring countryside that require no description. Then, last summer, some of the lagoons burst. In one case, 1.5 million gallons of manure found its way into the Iowa river, polluting 40 miles of water and slaughtering fish.
The result was uproar, and pressure intensified to tighten state laws governing the pig mega-farms. But the problem will not be easily solved. The clamour reflects a sad and perhaps irreversible fact of life - that the small independent family farm, once picture-postcard symbol of the values and virtues of the American Mid-West, is an institution facing extinction.
These days, they are being muscled aside by giant conglomerates, or simply folded into them. The Iowa of Field of Dreams and The Bridges of Madison County may appear hog and corn heaven. In fact, only 10 per cent of the state's 2.8 million people live on farms. Iowa exports more industrial goods than agricultural products.
Battered by the farm crisis of the 1980s, and unable to match the economies of scale of the producers, many family farms had no choice but to sign up with the food processors. In doing so, the link between farmers and their land has been broken. They have been turned into subcontractors, suppliers of raw materials in quantities and at prices dictated by others. Hence the colossal "hog confinement units".
But they do provide jobs of a kind. Make life tougher for "Big Pork", Iowa's Republican Governor Terry Branstad has warned, and the business will simply take off for places like the south-eastern US, eager to attract new business and less squeamish about nasty smells. Thus would the decay of Iowa's traditional agriculture merely be hastened.
Not surprisingly, the presidential candidates have mostly ducked the issue. The rise of vertically integrated agri-business concerns like Cargill, Ralston-Purina, and Archer Daniels Midland has been in part due to farm legislation by Congress. Bob Dole, from rural Kansas and often dubbed "the Senator from ADM," has been notably quiet on the pig wars. Pressed on the issue, Steve Forbes insists the problem "is for the state of Iowa to decide" - reasonable enough for a man who has declared war on meddling by the "Jurassic Park" that is Washington DC, but weasel words nonetheless.
Only Pat Buchanan has spoken out forthrightly, calling the giant hog confinement areas "factories, not farms". Therein perhaps lies hope for opponents: if the places can be defined as factories, they will become liable to much stricter industrial pollution rules. Meantime, Mr Buchanan's sympathy for the old-fashioned farmer may be one reason for his apparent success here.