WASHINGTON (AP) The Senate overwhelmingly approved a $275,000-per-farm cap on agriculture subsidies on Thursday, threatening the future of a Democratic farm bill. Under existing rules, farms can receive unlimited subsidies for production of grain, cotton and soybeans, and growers can get $80,000 more under a separate program that provides fixed annual payments. Southern Democrats trying to protect subsidies to large cotton and rice operations threatened to abandon the bill if the payment limit were approved. But a move to kill the cap failed 66-31, and the Senate then passed it on a voice vote.