The nation’s farmers are expected to boost corn plantings this year by about 2.5 million acres, signaling ample feed supplies for livestock producers.

An increase in corn acreage is “likely,” said Marty Foreman, Doane Advisory Services analyst, citing recent farmer surveys and a decline in winter wheat plantings. He projects corn planting at 89 million acres in 2010, up from 86.5 million in 2009.

Wet weather led to a drop in winter wheat seedings in the eastern half of the Midwest, freeing up land for other crops this spring. Additionally, crop budgets through the winter “indicated slightly higher returns for corn over soybeans,” Foreman said.

USDA will release its annual Prospective Plantings Report at 7:30 a.m. Central time on March 31.

Traders and analysts are gearing up for another summer crop season following a year when farmers reaped record corn and soybean harvests despite heavy rain and snow that forced widespread planting and harvest delays.

Corn and soybean futures have tumbled from last year’s highs as the grain supply outlook improved, and prices may sink further if Midwest farmers can return to their fields in timely fashion. Still, weather concerns probably will underpin prices for the time being, analysts said.

“Wet planting conditions have plagued corn farmers the past two years and we’re set for another slow start to the planting season due to wet soils,” Foreman said.

Even with “normal” weather this year, he projects average U.S. corn yields will fall to 161 bushels an acre from 164.9 bushels in 2009. Foreman projects corn production at 13.112 billion bushels, little changed from a last year’s record 13.13 billion bushels.

December corn futures, which reflect expectations for this year’s harvest, traded around $3.94 a bushel at mid-week, down from $4.40 ¾ at the end of last year.

November soybeans traded near $9.27 ¼ a bushel earlier this week, after ending 2009 at $10.14 ¼.

Soybean plantings are also set to increase, said Dan Cekander, director of grain research for Newedge Group in Chicago. He projects soybean plantings of 78.5 million acres in 2010, up from 77.5 million in 2009.

The outlook for higher corn and soybean acreage suggests “adequate” feed supplies for livestock producers, Cekander said.

November soybean futures have longer-term downside potential below $8.50, while December corn could slip to $3.60 to $3.70, Cekander said. “If the crop goes in on time, you could have $3 to $3.20” corn futures, he said.

“Longer term, we’re building carryout,” Cekander said.

Additionally, demand for corn and soybean meal may weaken because beef and pork producers have trimmed herds following a money-losing year.

That indicates USDA’s estimate for corn feed use during the 2009/2010 marketing year, at 5.55 billion bushels, is too high, Cekander said.

“I don’t think you have the animal numbers to support the USDA’s feed number,” he said.