A rotary cultivator is disclosed which is adapted to be supported upon a rear-mounted tractor hitch. The cultivator includes a tined cultivation shaft and a hydraulic motor and drive mechanism for driving one end of the shaft. The cultivator includes an arrangement for selectively varying the speed ratio of the hydraulic motor and cultivation shaft, as well as for selectively changing the length of the cultivation shaft so that the width of the path of soil cultivation may be changed as desired. A pair of spaced, negatively angled ground-engaging surfaces are provided on the cultivator housing for urging the cultivator downwardly during forward movement thus providing a more uniform depth of penetration during soil cultivation.