Dick Thompson stands on the edge of the concrete manure pit he built in his field, a high point here in the middle of Iowa, and gestures toward the piles.

Against the far wall is a contribution from the nearby town of Boone -- human bio solids that Thompson uses as fertilizer along with the manure he collects from his own hogs and cattle, some still steaming in the cold November air.

"What comes from the land," he says with a glint in his eye, "should be returned to the land."

Thompson, 81, doesn't farm like his neighbors. But his 300 acres have become a destination for farmers and scientists from around the world who come to witness something exceedingly rare in the Midwestern corn belt -- a diversified farm.

By working with nature rather than against it, Thompson has carved out a middle ground between the extremes of organic purism and the chemically intensive agriculture that is the norm in the Midwest. In so doing, agronomists say, he is modeling a kind of sustainable farming that could show a way forward in the divisive debate around the loss of the prairie, global food demand and agriculture's impact on land and water.

The prairie -- an ecosystem on a par with the rainforest and a terrain that kept water clean and built the rich soils of the corn belt -- is long gone. But scientists say that more farms like Thompson's could do much to replicate those same valuable ecological services that the natural landscape once provided.

Agricultural researchers have now put a decade's worth of numbers to Thompson's style of farming, one that is not organic but has succeeded with minimal use of pesticides and fertilizers. They found that it's just as profitable and just as productive, if not more so, than relying on chemicals and genetic technology. Plus, over time, it's 200 times less toxic to water.

"It's a pragmatic middle approach," said Jonathan Foley, who heads the University of Minnesota's Institute on the Environment. Because now, he said at a recent talk on the state of agriculture, "It's all or nothing."

Blind alley?

There was a time, Thompson says, when he farmed like everyone else. He bought fertilizer and pesticides by the bag, and planted corn year after year after year. But then, in the late 1960s, he went to a meeting where a speaker predicted that those chemicals would turn out to be a blind alley for farmers.

That's when he realized, he said, "The answer is not in a bag."

Today, a satellite view of the Upper Midwest would show a checkerboard landscape in just two colors - corn and soybeans. It reflects a transformation driven by genetic and chemical technologies that do come in a bag, as well as federal crop subsidies and mandates for ethanol. The combination has produced record amounts of those commodities at record prices, and a cleaner burning fuel.

"In that artificial system, farmers would be crazy not to grow more corn," Foley said. "That's how we make more money."

It is also driving a massive conversion of the nation's few remaining grasslands into chemical-intensive row crops. Since 2008, some 37,000 square miles of grasslands, wetlands and shrublands have been converted to agriculture, according the Environmental Working Group in Washington, D.C. Minnesota and the Dakotas alone lost an area the size of Connecticut.

Now, however, there are signs that the strategy may have reached that blind alley Thompson was warned of years ago. Weeds and insects have evolved to become resistant to the latest poisons, forcing farmers to use even more chemicals on the land. And despite increasing conservation efforts on the part of farmers, water throughout the Midwest is contaminated with agricultural fertilizers, pesticides and soil.

These days Foley makes a circuit around the country, from the Aspen Environment Forum in Colorado to the Minnesota Agri-Growth Council's annual meeting, urging a new, more efficient global strategy for agriculture that, like Thompson's, blends the best of organic with the technical power of conventional.

"The American corn belt is not feeding many people," he said. "It's feeding a lot of cars and cows. How long can we keep doing that?"

Five crops, four years

Forty years ago, just as the revolution in agriculture was about to take off, Thompson went in the other direction. He started farming much the way his father had on the same 300 acres. Instead of just two crops, corn and soybeans, he has honed a strategy that includes annual rotations of four crops in five years - corn, soybeans, hay and oats. Crop rotation prevents insects from gaining a foothold in his fields; alfalfa and soybeans help restore the soil's natural chemistry.

Thompson doesn't buy fertilizer -- he gets it from his animals and from town, and it's better for the soil because it contains more organic matter. He controls weeds with cover crops and with a specialized system of tilling and planting.

And he makes a profit: An average of $218 per acre since 2000 -- without federal subsidies -- compared with an average loss of $10 per acre in Boone County, by his calculations. The difference is the money he doesn't spend on fertilizers and pesticides.

"They spend too much money for stuff," he said.

Of course, it's taken him years to figure it out, and to track his progress with meticulous care in a stack of black notebooks. He's bought specialized equipment from Europe and built the manure pit. And had to deal with the watermelons and tomato plants that suddenly popped up in his fields from seeds that came through the sewage treatment process in Boone.

It also requires a lot more time and daily management, plus livestock to eat the oats and alfalfa, for which there isn't much of a market anymore.

Which makes some question how many farmers would adopt Thompson's methods.

"That's the way my dad farmed in the 1950s and '60s," said Robert Plathe, a corn and soybean farmer west of Mason City. "If I have a market, that makes sense," he said. It would also help revive agricultural communities because farms would be smaller and more families could live off the land.

But, he pointed out, it's a lot harder, and few people want to farm like that anymore. Animals require daily care, winter and summer.

"Farmers like their free time in the winter," he said.

More labor, less pollution

Mixed farming does require more work -- a third more in labor costs, according to a study published in October that compared diverse farming with conventional. But the payoff in other respects was substantial, said Matt Liebman, an Iowa State University agronomist who's studied Thompson's techniques and who led the research. Planting four different crops over four years resulted in a 92 percent reduction in fertilizer and a 97 percent reduction in herbicides, Liebman found.

And during the last six years of the study, the reduction in herbicides resulted in a 200-fold decline in water toxicity.

Between 2003 and 2011, revenues on the experimental farm were lower for the diverse cropping system because crops like alfalfa and oats pay less than corn and soybeans. But overall, profitability was about equal, Liebman said, because of much less need for expensive fertilizers and other chemicals.

"Very small quantities of chemicals, when combined with ecological processes, can have powerful effects," he said.

Jason Hill, a plant biologist at the University of Minnesota who participated in the Marsden Farm study, said it shows that agriculture has come full circle. Farmers have always known that nature can be their ally -- they have understood the value of animals on the land and diversity in their fields. But in recent decades that philosophy gave way to chemistry and genetic engineering -- "which have major negative consequences," he said. In fact, said Foley, finding a way to feed the world without destroying it rivals climate change among today's most pressing environmental challenges.

But at Thompson's farm in the middle of Iowa, the answer is simple: Use nature, he said, "and then if you need to, use pesticides as a last resort." And return to the land what came from the land, even if it includes watermelon seeds.

Josephine Marcotty • 612-673-7394