The Secretary is authorized to administer a special wheat acreage grazing and hay program (hereinafter in this section referred to as the “special program”) in each of the crop years 1978 through 1990. If a special program is implemented, a producer shall be permitted to designate, under such regulations as established by the Secretary, a portion of the acreage on the farm intended to be planted to wheat, feed grains, or upland cotton for harvest, not in excess of 40 per centum thereof, or 50 acres, whichever is greater, which shall be planted to wheat (or some other commodity other than corn or grain sorghum) and used by the producer for grazing purposes or hay rather than for commercial grain production. A producer who elects to participate in the special program shall receive a payment as provided in subsection (c) of this section.