(a) General rule
Not later than 120 days after November 9, 1978, the Secretary of Energy shall prescribe and make effective a rule, which may be amended from time to time, which provides that, notwithstanding any other provision of law (other than subsection (b)) and to the maximum extent practicable, no curtailment plan of an interstate pipeline may provide for curtailment of deliveries of natural gas for any essential agricultural use, unless such curtailment—

(1) does not reduce the quantity of natural gas delivered for such use below the use requirement specified in subsection (c); or

(2) is necessary in order to meet the requirements of high-priority users.

(b) Curtailment priority not applicable if alternative fuel available
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.

(c) Determination of essential agricultural use requirements
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.

(d) Authority of Secretary of Agriculture to intervene
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).

(e) Limitation
The Secretary of Agriculture may not exercise any authority under this section for the purpose of restricting the production of any crop.

(f) Definitions
For purposes of this section—

(1) Essential agricultural use
The term "essential agricultural use", when used with respect to natural gas, means any use of natural gas—

(A) for agricultural production, natural fiber production, natural fiber processing, food processing, food quality maintenance, irrigation pumping, crop drying, or

(B) as a process fuel or feedstock in the production of fertilizer, agricultural chemicals, animal feed, or food,

which the Secretary of Agriculture determines is necessary for full food and fiber production.

(2) High-priority user
The term "high-priority user" means any person who—

(A) uses natural gas in a residence;

(B) uses natural gas in a commercial establishment in amounts of less than 50 Mcf on a peak day;

(C) uses natural gas in any school, hospital, or similar institution; or

(D) uses natural gas in any other use the curtailment of which the Secretary of Energy determines would endanger life, health, or maintenance of physical property.