Chicago Board of Trade (CBOT) grains futures closed lower on Monday with May wheat delivery falling 2.27 percent, the biggest decrease on a percentage basis since last October.

The most active corn contract for May delivery fell 3.25 cents, or 0.89 percent, to 3.61 dollars per bushel. May wheat delivery fell 10 cents to 4.305 dollars per bushel. May soybeans dropped 0.5 cent, or 0.05 percent, to 10.06 dollars per bushel.

Russia's ruble is slightly weaker on Monday as its Black Sea wheat reportedly suffered little winterkill damage, which makes Russian wheat more competitive.

Weather forecast of much-needed rain later this month in the southern plains of the U.S. is a good news for wheat-planting farmers there, but dragged the grain futures much lower.

Corn followed the weak trend, with soybean almost unchanged.

The May delivery corn declined to a new low since February, as supplies remain ample in the world market.

It was a mostly quiet day in the soybean market. Having seen huge yields in both the U.S. and Brazil, the trade is switching its attention to the Argentine crop.