The Secretary shall provide for ascertaining, by measurement or otherwise, the acreage of any agricultural commodity or land use on farms for which the ascertainment of such acreage is necessary to determine compliance under any program administered by the Secretary. Insofar as practicable, the acreage of the commodity and land use shall be ascertained prior to harvest, and, if any acreage so ascertained is not in compliance with the requirements of the program the Secretary, under such terms and conditions as he prescribes, may provide a reasonable time for the adjustment of the acreage of the commodity or land use to the requirements of the program. Where cotton is planted in skiprow patterns, the same rules that were in effect for the 1971 through 1973 crops for classifying the acreage planted to cotton and the area skipped shall also apply to the 1974 through 1995 crops, except that, for the 1991 through 1995 crops, the rules shall allow 30 inch rows (or, at the option of those cotton producers who had an established practice of using 32 inch rows before the 1991 crop, 32 inch rows) to be taken into account for classifying the acreage planted to cotton and the area skipped. For the 1992 through 1995 crops, the rules establishing the requirements for eligibility for conserving use for payment acres shall be the same rules as were in effect for 1991 crops.