Southern senators formed a nearly monolithic block against the amendment, with the exception of Florida (Nelson) and Virginia (Warner and Webb). This provided 22 of the 41 votes needed to sustain the filibuster. The remainder of the filibuster squad came from the far west, far north, and center of the country.
What is it about the South that created a bipartisan voting block against reform?
Four forces: cotton, peanuts, rice — and subsidies. The bulk of these crops are grown in the states represented by senators who voted No on the reform amendment. They had much more to lose financially from payment limits than even corn- and soy-growing states in the Midwest.