A retractable in-row tiller device is adapted for mounting on a movable vehicle and for tilling the ground around and between objects in a row. An outrigger arm with a rotary tiller mounted on its distal end is retracted inwardly and extended outwardly by a trapeze-type control arm which amplifies the velocity and magnitude of reciprocal motion produced by a hydraulic ram to move around and avoid objects encountered in the row. Both manually and automatically operable controls are included respectively to allow an operator to retract and extend the tiller out of and into the row as desired and to cause the tiller to be retracted and extended out of and into the row automatically upon encountering an object in the row. Manual control is also provided for the operator to override the automatic retraction control.
A lift mechanism for lifting the tiller out of the ground and a rotary drive for rotating the tiller are interrelated such that the vertical lift force is variable in relation to the force required to rotate the tiller. The ratio between the lifting force and the rotary drive is adjustably variable to effect automatic depth control for ground penetration.
An additional feature includes a positive depth control plate for the rotary tiller head, and alternative embodiments include a pair of parallel spaced-apart linear chain tillers which move in opposite directions transverse to the forward motion of the vehicle with one chain tiller following the other.