If the Commission, in consultation with the Secretary of Agriculture, determines, by rule or order, that use of a fuel (other than natural gas) is economically practicable and that the fuel is reasonably available as an alternative for any agricultural use of natural gas, the provisions of subsection (a) shall not apply with respect to any curtailment of deliveries for such use.
The Secretary of Agriculture shall certify to the Secretary of Energy and the Commission the natural gas requirements (expressed either as volumes or percentages of use) of persons (or classes thereof) for essential agricultural uses in order to meet the requirements of full food and fiber production.
The Secretary of Agriculture may intervene as a matter of right in any proceeding before the Commission which is conducted in connection with implementing the requirements of the rule prescribed under subsection (a).
The Secretary of Agriculture may not exercise any authority under this section for the purpose of restricting the production of any crop.