U.S. wheat fell for a fifth straight session on Wednesday to a new 5-1/2 year low due to a large global supply of the grain and sagging financial markets.

Corn and soybeans fell for a second day, pressured by the prospect of bumper crops in South America coming onto the market, although trading was cautious ahead of closely watched U.S. government planting forecasts due on Thursday.

Chicago Board of Trade front-month wheat had eased 0.5 percent to $4.46 a bushel by 1135 GMT, after earlier touching its lowest since June 2010 at $4.45-3/4. The contract had closed down 2.3 percent on Tuesday.

The more active May contract was down 0.3 percent at $4.54-1/4 after also recording its lowest since June 2010 at $4.54.

In Europe, benchmark May wheat on Euronext fell to a new contract low of 155.50 euros a tonne while spot March set a contract low of 148.75 euros as it slipped below the important 150 euros chart level.

Selling pressure built up on Tuesday during a broad slide in commodity and share prices, and as mostly favorable conditions for U.S. and European wheat being grown for the next harvest reinforced bearish supply sentiment.

"The market's reluctance to sell clearly gave way yesterday as the reality of heavy origin inventories weighed," said Tobin Gorey, director of agricultural strategy, Commonwealth Bank of Australia.

Rains in Oklahoma and Texas, two key U.S. wheat-producing states, were notably seen as beneficial to hard red winter wheat by alleviating dryness.

On the demand side, U.S. and European wheat exports are seen as too modest to bring down high inventories.

"Ferocious competition abroad is dragging global wheat prices lower, as weaker currencies have provided Black Sea and Argentinian exporters with a tremendous competitive advantage over the U.S.," Rabobank analysts said in a note.

Front-month soybeans fell 0.1 percent to $8.68 a bushel, and spot corn fell 0.3 percent to $3.61 a bushel.

Traders were awaiting the U.S. Department of Agriculture's (USDA) acreage forecasts for spring planting of corn and soybeans.

Despite low prices, U.S. farmers are expected to grow more of the country's top two crops this year as they scramble to stay solvent, a Reuters poll of analysts indicated.

Bearish sentiment in oilseed markets was also reinforced by news that China plans to toughen its standard for imported Canadian canola starting on April 1, a move that traders and analysts in China see as linked to a push to cut local stocks.