Spot corn basis bids at elevators and processors were unchanged around the US Midwest on Thursday and steady to firmer for soyabeans, grain merchants said. Farmer sales subsided for both crops after profit-taking pressured Chicago Board of Trade corn while brisk US exports drove up soyabeans futures. Soyabean bids at western river elevators drew support from increased demand, partly fueled by concern that frigid temperatures may slow down barge traffic headed south to the US Gulf.