Chicago Board of Trade (CBOT) grains futures closed lower on Thursday with soybean futures falling to one and half months low, pressured by a sharp drop in crude oil prices.

Corn futures also weakened, with investors beating down early rally attempts due to ample global supplies and signs of poor export demand.

The most active corn contract for July delivery fell 2 cents, or 0.54 percent, to 3.6925 dollars per bushel. July wheat delivery went down 1.75 cents, or 0.4 percent, to close at 4.3075 dollars per bushel. July soybeans dropped 8.75 cents, or 0.92 percent, to close 9.395 dollars per bushel.

In the outside markets, the Brent crude oil market is 2.51 dollars per barrel lower, the U.S. dollar is higher, and the Dow Jones Industrials are 80 points higher.

"There's too much corn and beans and wheat in the world," said Tomm Pfitzenmaier, founding partner at Summit Commodity Brokerage. Rallies are going to be "blunted" as a result, he said.