In any case in which the ownership of a tract of land is transferred from a parent farm, the acreage allotments, history acreages, and base acreages for the farm shall be divided between such tract and the parent farm in the same proportion that the cropland acreage in such tract bears to the cropland acreage in the parent farm, except that the Secretary shall provide by regulation the method to be used in determining the division, if any, of the acreage allotments, histories, and bases in any case in which—

(1) the tract of land transferred from the parent farm has been or is being transferred to any agency having the right to acquire it by eminent domain;

(2) the tract of land transferred from the parent farm is to be used for nonagricultural purposes;

(3) the parent farm resulted from a combination of two or more tracts of land and records are available showing the contribution of each tract to the allotments, histories, and bases of the parent farm;

(4) the appropriate county committee determines that a division based on cropland proportions would result in allotments and bases not representative of the operations normally carried out on any transferred tract during the base period;

(5) the parent farm is divided among heirs in settling an estate; or

(6) neither the tract transferred from the parent farm nor the remaining portion of the parent farm receives allotments in excess of allotments for similar farms in the community having allotments of the commodity or commodities involved and such allotments are consistent with good land uses.