7 USC 1310 - American agriculture protection program

(a) Determination of short supply; suspension of commercial export sales; parity price 
Notwithstanding any other provision of law, whenever the President or any other member of the executive branch of the Federal Government causes to be suspended, based upon a determination of short supply, the commercial export sales of any commodity, as defined in subsection (c) of this section, to any country or area with which the United States otherwise continues commercial trade, the Secretary of Agriculture shall, on the day the suspension is initiated, set the loan level for such commodity under the Agricultural Act of 1949, as amended [7 U.S.C. 1421 et seq.], if a loan program is in effect for the commodity, at 90 per centum of the parity price for the commodity, as such parity price is determined on the day the suspension is initiated.
(b) Duration of loan level 
Any loan level established pursuant to subsection (a) of this section shall remain in effect as long as the suspension of commercial export sales described in subsection (a) of this section remains in effect.
(c) “Commodity” defined 
For purposes of this section, the term commodity shall include any of the following: wheat, corn, grain sorghum, soybeans, oats, rye, barley, rice, flaxseed, and cotton.