Chicago Board of Trade wheat futures closed lower on Thursday, erasing most of the previous day's short-covering rally as traders returned their focus to plentiful global supplies. CBOT September wheat settled down 7 cents at $4.03-1/4 per bushel. K.C. hard red winter wheat and MGEX spring wheat futures followed CBOT wheat lower.Disappointing weekly US export sales added pressure. The US Department of Agriculture reported export sales of US old-crop wheat in the week to July 28 at 326,500 tonnes, below trade expectations for 350,000 to 650,000 tonnes.