Notwithstanding any other provision of law, the Secretary shall permit any producer who is participating in the wheat program under title IV of this Act, in the feed grain program under title V of this Act, or in the cotton program under title VI of this Act, in any year in which an acreage diversion or set-aside program is in effect, under any such program in which such producer is participating, subject to the conditions prescribed in subsection (b) of this section, to plant and harvest hay from 25 per centum of the acreage on the farm diverted from production under such programs or twenty-five acres, whichever is greater.