Chicago Board of Trade (CBOT) grains futures closed lower on Wednesday with plentiful global stocks and expectations of a robust harvest casting a bearish tone over the market.

Wheat posted the biggest losses, falling below key technical support points as forecasts for rain in the U.S. Plains drove prices down 2.0 percent to one-week lows.

Corn notched its third straight day of declines as investors struggled to find a reason to push prices above the eight-month highs hit last week.

The most active corn contract for May delivery fell 3.75 cent, or 1.00 percent, to 3.7225 dollars per bushel. May wheat delivery fell 9.5 cents, or 2.08 percent, to 4.47 dollars per bushel. May soybeans dropped 3.5 cents, or 0.34 percent, to 10.2175 dollars per bushel.

In the outside markets, the Brent crude oil market is 2.86 dollars per barrel lower, the U.S. dollar is higher, and the Dow Jones Industrials are 49 points lower.

Deanna Hawthorne-Lahre, StatFutures co-founder and trader, says that macroeconomics are partly to blame for the lower grain markets.

"The U.S. dollar strength is finally getting the market' s attention. A signaled interest rate hike, and the ADP Report, a report that measures levels of nonfarm private employment, is showing strong numbers. All are weighing on the markets," Hawthorne-Lahre says.

Investors were reluctant to make big bets ahead of the U.S. Agriculture Department's monthly supply and demand report on Thursday.

Farming agency FranceAgriMer increased its forecast for French soft wheat stocks this season for the second month in a row as increased imports and reduced export prospects within the European Union outweighed improving exports elsewhere.

Soybean futures hit their lowest level since Feb. 27, with crop forecasts for the Brazilian harvest issued earlier this week continuing to weigh on prices.

The 2016/17 Brazilian soybean crop could reach 109.07 million tonnes, almost 15 million tonnes more than in the previous season, as record yields in several states boost output prospects, broker and analyst INTL FCStone said on Tuesday.