Abstract: An adjustable depth control mechanism for use with earth penetrating equipment. The invention includes a hub and spindle assembly for use with an adjustable depth gauge wheel, which is mounted on a support axle. It may also include a position indicator that an operator can readily view to determine the relative position of the depth gauge wheel and, accordingly, the depth setting of the ground penetrating disc. The indicator rotates to certain positions that correspond to the depth to which the disc is allowed to penetrate into the ground. Preferably, both the position indicator and the adjustment mechanism of the assembly are located internal to the depth gauge wheel and are covered and protected by the rim of the wheel from contamination by soil and crop residue.