U.S. farmers are likely to plant 3.0% more corn acreage this year than last year, but only 0.7% more soybean acreage, raising concerns soybean supplies could tighten as the year goes on, according to analysts polled by Dow Jones Newswires.

Analysts on average expect the U.S. Department of Agriculture, in the results of a planting-intentions survey due Friday, to forecast U.S. corn plantings of 94.7 million acres this year, up from 91.9 million acres last year and the USDA's previous prediction of 94 million acres. Estimates given by 20 analysts in the Dow Jones poll ranged from 93.7 million to 95.7 million acres.

The USDA is due to release the planting report and recent grain and soy inventory figures at 8:30 a.m. EDT Friday.

"You've got a huge report coming up," said Kurt Koester, president of brokerage AgriSource, in West Des Moines, Iowa. "It's as important as ever in determining where prices go from here."

Farmers may plant extra corn because corn prices have been high relative to soy in recent months, and because warm weather coming early to the Midwest this year has encouraged extra corn planting, analysts have said.

That has led to analyst concerns soy acreage won't be high enough to ensure ample supplies after the fall harvest. Drought in South America has led analysts to cut their estimates for this year's soy output in Brazil and Argentina--and to expect more export demand for U.S. soybeans as a result.

Analysts in the poll on average expected the USDA to forecast soybean plantings of 75.5 million acres, up slightly from 75.0 million acres last year and from the USDA's last prediction plantings would stay at that level. Estimates by 20 analysts ranged from 74.5 million to 76.7 million acres.

"We can't afford any crop stress, any crop problems, any shortfall in acreage," said Rich Feltes, vice president for research at futures broker R.J. O'Brien in Chicago. "If the bean acreage on Friday is not a bearish surprise...that is going to be basically a signal for funds" to keep buying soybeans, he said.

Analysts in the poll on average expected the USDA to estimate total plantings of wheat to be harvested in 2012 at 57.6 million acres, up from 54.4 million acres last year and down from the USDA's previous forecast of 58 million acres.

For wheat, traders will be most focused on the USDA's durum and spring-wheat planting forecasts. Polled analysts on average expected spring-wheat plantings of 13.4 million acres, up from 12.4 million acres a year earlier, and durum plantings of 2.3 million acres, up from 1.4 million acres.

Meanwhile, analysts on average expect the USDA's inventory figures, given as of March 1, to reflect lower on-hand supplies of corn and wheat than a year earlier, and higher current soybean supplies.

Analysts expect corn stocks to be 6.15 billion bushels, down from 6.52 billion bushels a year earlier. They see wheat stocks at 1.24 billion bushels, down from 1.43 billion bushels, and soybean stocks at 1.38 billion bushels, up from 1.25 billion bushels.