Joe Waldman is saying goodbye to corn after yet another hot and dry summer convinced the Kansas farmer that rainfall won't be there when he needs it anymore.

"I finally just said 'uncle,' " said Waldman, 52, surveying his stunted crop about 100 miles north of Dodge City. Instead, he will expand sorghum, which requires less rain, let some fields remain fallow and restrict corn to irrigated fields.

While U.S. farmers planted the most corn this year since 1937, growers in Kansas sowed the fewest acres in three years, instead turning to less thirsty crops such as wheat, sorghum and even triticale, a wheat/rye mix popular in Poland. Meanwhile, corn acreage in Manitoba, about 700 miles north of Kansas, has nearly doubled over the past decade as Canadian farmers react to weather changes and higher prices.

Shifts such as these reflect a view among food producers that this summer's drought in the United States -- the worst in half a century -- isn't a random disaster. It's a glimpse of a future altered by climate change that will affect worldwide production.

"These changes are happening faster than plants can adapt, so we will see substantial impacts on global growing patterns," said Axel Schmidt, a former senior scientist for the International Center for Tropical Agriculture now with Catholic Relief Services.

While there still is debate about how human activity is altering the climate, agriculture is already adapting to shifting weather patterns.

Agribusiness giant Cargill Inc. is investing in northern U.S. facilities, anticipating increased grain production in that part of the country, said Greg Page, CEO of the Minnetonka-based company.

"The number of rail cars, the number of silos, the amount of loading capacity" all change, Page said in an interview. "You can see capital go to where there is the ability to produce more tons per acre."

Wheat was the only choice

Losses in some areas will mean gains in others, Page said. A native of Bottineau, a small town on North Dakota's border with Canada, Page said that when he was in high school in the 1960s, "you could grow wheat -- or wheat. That was it.

"You go to that very same place today -- they can grow soybeans, they can grow canola, they can grow corn, they can grow field peas and export them to India. A lot of that has been to do with the fact that they have six, eight days more of frost-free weather."

For the most part, the country's midsection will remain the nation's Corn Belt, said Jerry Rowe, manager of the Heritage Grain Cooperative in Dalton City, Ill., traditionally the second-biggest corn-producing state.

"I don't have a place to store pinto beans, OK?" said Rowe, who has managed his community's grain elevator for 25 years. "This is corn and soybean ground. The reason someone else is more diverse is because there's more money in being diverse. It's all economics."

Still, the hotter, drier weather pattern may change crop rotations even in the heart of the Corn Belt. "Wheat acres will be very high" next year, said Tabitha Craig, who sells crop insurance in New Hartford, Mo.

Climate change will probably push corn-growing regions north while making alternatives to the grain more important elsewhere, said John Soper, vice president of crop genetics research and development for Pioneer, the seed division of DuPont Co.

The company is developing new varieties of corn while boosting research in sorghum and other crops that don't need irrigation, he said.

Still, fighting drought with better seeds and new trade sources only mitigates the effects of climate change, said Roger Beachy, a plant biology professor at Washington University in St. Louis. New crops -- and new markets for those crops -- will be needed to ease what will be a wrenching transition for some farmers and consumers, he said.

"We need to use biodiversity and crop varieties to our advantage," said Beachy. "Can a farmer make as much money raising chickpeas as corn? You have to create value for the farmer. We need to get the scientists and the economists talking to one another about this."