Abstract: An agricultural apparatus comprises a main frame with ground wheels supporting the frame for movement across the ground and a plurality of ground engaging openers mounted on the frame for engaging the ground. Each opener includes a depth control wheel mounted on the opener frame member for movement in a direction for varying the height of the depth control wheel on the opener frame member to vary the depth of the opener element in the ground. A common adjustment apparatus for all the depth control wheels comprises an actuator, a common drive linkage mounted on the main frame and driven by the actuator and a plurality of individual adjustment members. A cam plate operable by the adjustment member. The depth control wheel is mounted on an arm on which is pivotally mounted on the opener frame member on a first pivot pin, the arm including a portion thereof for engaging the cam plate.