The Interior Department has proposed two alternatives for controversial regulations governing the reclamation of farmland that has been strip mined. Under 1977 surface mining law, Interior was supposed to set a date after which all prime farmland had to be returned to its former level of productivity after it was strip mined. The only problem is coming up with a date, a process the department has repeatedly delayed since the Reagan administration took office.

One of the department's recent proposals would set Aug. 3, 1982 as the date; the other would let the states set it. Illinois, which has tough strip-mining laws, wants a national standard so its mine owners won't be penalized by weaker rules elsewhere. Actually, says Assistant Secretary Daniel N. Miller, there's a third option: setting no date, leaving things as they are.

Conservation groups support the August date. "Hundreds of thousands of acres of prime farmland will be lost without this deadline," said Norman L. Dean, counsel to the National Wildlife Federation. "The Reagan administration unlawfully held up the regulation in the first place, and now they're trying to come up with ways to delay even more." The department plans an April 15 hearing on the options.