Prices for grains and other agricultural commodities will probably continue rising in 2011 as “precariously balanced” fundamentals and a La Nina phenomenon contribute to wide price swings, Rabobank analysts said.

Corn, soybeans and coffee hold the most potential upside among about 10 commodities, Rabobank Agri Commodity Markets analysts led by Luke Chandler said in a Dec. 21 report. While corn, soybean and wheat supplies appear sufficient for the time being, record crops are likely needed next year to keep inventories from tightening further.

Favorable weather conditions “are necessary for almost all agricultural commodity markets in 2011 to rebuild inventory levels and prevent a rally in prices back to the highs of the 2007/2008 commodity boom,” the London-based analysts said.

Corn is expected to average $6 a bushel during the first quarter of 2011 and $5.80 during the second quarter, up from $5.50 so far in the current quarter, the analysts said. Soybeans are expected to average $13 a bushel in the first quarter and $12.75 in the second quarter, up from $12.15 during the fourth quarter of 2010.

Rabobank “maintains a constructive outlook on agricultural commodity prices into 2011, with precariously balanced fundamentals in a number of markets setting the stage for higher prices in the year ahead,” the report said.

“But as in 2010, we expect bearish macro headwinds will lead to further price uncertainty and continued heightened volatility, making the road to higher prices a bumpy one,” the report said. Rabobank is based in the Netherlands.

Corn futures are already up 46 percent this year, reflecting a disappointing U.S. harvest, strong exports and a drought that slashed Russia’s grain production. U.S. corn stocks are expected to fall to a 15-year low in 2011, according to government estimates.

Near today’s close, March corn futures in Chicago rose 5 ¼ cents to $6.07 ½ a bushel, after earlier reaching $6.09 ¾, the contract’s highest price since Nov. 9. January soybeans rose 3 cents to $13.29 ¼ a bushel.

Additionally, one of the strongest La Niña patterns in the past 50 years has fueled concern over crop shortfalls in some key growing areas. La Nina has been linked to dryness in Argentina and Brazil, two top corn and soybean growers.

“Global inventory levels for a number of agricultural commodity markets are at or nearing record‐low levels,” the analysts said. “And with robust demand growth from emerging market economies – particularly China – agricultural prices are likely to be extremely sensitive to any further weather or policy‐induced supply shocks.”

With several agricultural commodities in need of expanded production to rebuild inventories, “significant” supply constraints are likely to emerge, Rabobank said. In the U.S., a “battle for acres” looms between corn, cotton, soybeans and wheat, likely straining availability of key crop inputs such as fertilizer and seed, the report said.

“There is a convergence of pressures building on land availability next season,” the analysts said. “Consequently, there will be winners and losers as not all of the supply issues can be solved in one season.”

The U.S. spring planting season is “shaping up to be a critical period for a number of markets, with increased planted area needed in a number of crops… to increase production sufficiently to meet domestic and world demands,” the report said.