Corn spot basis bids were steady to firm at processors and ethanol plants around the US Midwest on Wednesday, rising by as much as 5 cents per bushel in some areas, grain dealers said. Corn bids rose the most at a closely watched processor in Decatur, Indiana, with a bid 5 cents higher than earlier this week. Soyabean basis increased by 3 cents at the same location. Bids at ethanol plants in the US Midwest firmed slightly by a few cents.