A planter row unit has a pair of ground-engaging gauge wheels located in close proximity to opposite sides of a furrow opener of the unit. The depth of penetration of the furrow opener depends upon the vertical position of the gauge wheels relative to the furrow opener. Wheel arms that connect the gauge wheels to the frame of the row unit are operably coupled with a depth adjustment lever through a rigid link that transmits adjusting movement of the depth adjustment lever to the gauge wheels to raise or lower the same. The link is made adjustable in length to provide fine depth adjustment of the unit for calibration purposes or otherwise.