Implement rear hitch height and attitude control

Implement hitch height control structure to maintain a rear hitch point at a generally constant height as the implement is raised and lowered. In one embodiment, a rectangular hitch frame is pivotally connected at a forwardmost end to lever arms on the implement lift rockshaft. Linkage structure connected between the hitch frame and the implement frame help control hitch frame attitude, rear hitch point height and force transfer to the implement frame. The hitch frame is located substantially behind the implement rockshaft for minimal interference with tool placement on the frame and limited interference with trash and soil flow under the main frame. In another embodiment, linkage structure includes a second rockshaft connected generally above the aft end of the main frame.