Abstract: An improvement of a plow or a harrow of the type in which a plurality of saucer-like disks carried by a rotary shaft inclined at an angle with respect to the direction of travel of a tractor are forced to rotate, thereby plowing uncultivated farm land. The plurality of disks or disk gang is supported by a parallel linkage system and the angle of the disk gang with respect to the direction of travel of the tractor can be freely selected so that, in accordance with the skill of an operator and soil condition which will be encountered, either the horizontal travel or the inclined travel may be selected.