U.S. farmers will plant the most acres in a generation this year, led by the biggest corn crop since World War II, taking advantage of the highest agricultural prices in at least four decades.

They will sow corn, soybeans and wheat on 226.9 million acres, the most since 1984, a Bloomberg survey of 36 farmers, bankers and analysts showed. The 2.5- percent gain means an expansion the size of New Jersey, as growers target fields left fallow last year and land freed up from conservation programs.

Crop prices, some of which reached the highest averages ever in 2011, bolstered the economies of Midwest growing states, sent net farm income up 28 percent to $100.9 billion and pushed the value of farmland to a record $2,350 an acre, the U.S. Department of Agriculture estimates. Global food costs are down 11 percent from a peak a year ago as grain output rises from China to Canada, United Nations data show.

“There is unlikely to be any ground that won’t be planted this year,” said Todd Wachtel, a 40-year-old who farms about 5,700 acres in Altamont, Ill., and plans to expand his corn fields by 21 percent when seeding begins in early April. “Farmers know that they have to plant more when prices are high because they may not last.”

A bigger harvest in the U.S., the world’s largest exporter of all three crops, will help compensate for shortages in the current crop year. Drought damage in Brazil and Argentina will probably spur the USDA to cut its global and U.S. grain-supply forecasts for the current season on Feb. 9, a separate Bloomberg survey of as many as 25 analysts showed. The USDA’s first forecast for the 2012-2013 crop year will be Feb. 23.

Farmers will sow corn, used to feed livestock and make ethanol, on 94.329 million acres this year, up 2.6 percent from last year and the most since 1944, according to the Bloomberg survey. Soybean fields may expand 0.4 percent, to 75.309 million acres, the fifth-most ever. Both crops are harvested after the current season ends on Aug. 31. Wheat in the season that begins June 1 will reach a three-year high of 57.233 million acres, up 5.2 percent, the survey showed.

Corn may rise 7.1 percent, to $6.90 a bushel, in six months because of the damage in South America, before dropping to $5.25 in a year as U.S. farmers increase supply, Goldman Sachs Group Inc. said in a Feb. 2 report. Corn for delivery in December, after the harvest, fell 0.8 percent, to $5.765 Monday, 10 percent below the March contract on the Chicago Board of Trade.

Wheat may tumble 18 percent, to $5.50, by July and soybeans may drop 17 percent, to $10.20 a bushel, analysts at commodity broker Allendale Inc. in McHenry, Ill., said Jan. 21.

“The area is available to have huge crops this year,” said Paul Meyers, a vice president at Foresight Commodities Services Inc. in Long Valley, N.J., and the former head of grain-market analysis at the USDA from 1974 to 1983. “We are headed for a surplus-supply situation.”

Corn, soybean and wheat futures are down at least 15 percent since the end of August, helping to send the Standard & Poor’s GSCI Agriculture Index to a 16-percent decline. World food prices fell to a 14-month low in December, led by declines in grains, sugar and oilseeds, the UN’s Food and Agriculture Organization said Jan. 12.

Farmers in the Midwest, the main growing region, are less than two months away from planting seeds, and dry soils in some areas could limit output. The most widely-held option on December corn futures gives the holder the right to buy the grain at $7.

“It’s been an abnormally warm winter,” said Alan Tiemann, who is preparing to expand corn planting on his 2,000-acre farm in Seward, Neb., by 15 percent. “That may not relate to what’s going to happen this summer, but it keeps you on the edge of your seat a little bit, wondering when the next moisture event is going to happen.”

Corn averaged $6.79 in Chicago last year, the highest ever and twice the level of the previous decade, exchange data show. Soybeans averaged a record $13.21, 72 percent above the 10 previous years, while wheat’s average of $7.235 was the second- highest ever and 57 percent more than the past decade.

Money managers have been betting on lower wheat prices since September, U.S. Commodity Futures Trading Commission data show. They cut their bullish wagers on soybean and corn in two of the past three weeks.

Floods, drought and freezes last year prevented planting of the three crops on about 8.577 million acres, 28 percent more than in 2010, USDA data show. An additional 1.84 million acres that were planted failed to produce, more than double the amount a year earlier.

Crop insurers paid out a record $9.1 billion last year to cover the damage, and the bill may top $10 billion when all claims are settled, Overland Park, Kan.-based National Crop Insurance Services said Jan. 24.

A return to normal weather in 2012 would mean more production from last year’s lost acres. The government also has reduced the amount of land it pays farmers to leave fallow by 4.7 percent, adding 1.47 million acres that weren’t available in 2011, USDA data show.

Rising incomes allowed farmers to buy more land and the extra seed, crop chemicals and equipment needed.

“Grain farming has been one of few profitable industries for the past three years, and there will be a tendency for farmers around the world to maximize acreage,” said Don Roose, the president of U.S. Commodities Inc. in West Des Moines, Iowa, who has been advising farmers and grain elevators since 1979. “We have the potential to grow record world crops this year that can swamp demand.”

Deere & Co., the world’s largest farm-equipment maker, will report record net income of $3.14 billion this year, up from $2.8 billion a year earlier, the mean of eight analyst estimates compiled by Bloomberg shows. Shares of the Moline, Illinois- based company rose 14 percent this year.

Monsanto Co., the biggest seed company, will earn $1.9 billion, up from $1.61 billion, the mean of seven estimates shows. The St. Louis-based company rose 14 percent in New York trading this year.

Land prices in Iowa, the biggest corn- and soybean-growing state, averaged $5,600 an acre last year, three times the amount a decade ago, USDA data show.

While farming accounts for 0.9 percent of the U.S. economy, it has been among the fastest-growing contributors. The amount of value added by agriculture in the four years through 2010 rose 42 percent, to $132.6 billion, compared with 8.6-percent growth for the entire economy, government data show.

U.S. exports surged as global economic growth boosted demand for crops, meat and dairy products, while weather damage disrupted supplies of everything from Russian wheat to Chinese pork.

Shipments reached a record $137.4 billion in the year that ended Sept. 30, with China the largest farm-goods buyer, USDA data show. While the government expects a drop to $132 billion in the current fiscal year, that still would be the second-largest ever and 21 percent higher than when President Barack Obama set a goal in 2010 to double all U.S. exports by 2015.

Unemployment in Midwest states was 7.9 percent in December, tied with the Northeast as the healthiest job region. North Dakota, Nebraska and South Dakota were the only states with unemployment under 5 percent. The national rate fell to 8.3 percent in January from 8.5 percent in December.

Corn will lead the planting surge because it is the most profitable row crop. U.S. mandates for alternative fuels have led to an increased use of the grain to make ethanol, and rising worldwide incomes are boosting meat consumption, increasing requirements for livestock feed. Global production of beef, veal, pork, chicken and turkey will reach almost a quarter of a billion metric tons this year, 62 percent more than two decades ago, the USDA estimates.

An acre of corn will earn as much $150 more than soybeans at current prices and normal weather, said Mike Wagler, 30, who farms about 7,000 acres with his father in the southwestern Indiana town of Montgomery.

“Farmers have the capital to plant a big corn crop this year,” said Wagler, who plans to sow 85 percent of his family’s land with the grain compared with 70 percent last year. “We can make more money raising corn than soybeans.”