Abstract: A hydrostatic drive system for a four wheel drive vehicle such as a field harvesting machine which must accurately track the planting rows, includes an engine, a pump and individual hydraulic wheel motors connected to the pump and coupled to the wheels through a manually set free wheeling clutch. The motors are in series connection at each side of the vehicle, with the pairs of series connected motors on opposite sides of the vehicle in parallel connection with the pump. When the traction of a wheel on one side is reduced or lost, both wheels on that side continue to rotate at the same speed. Under these conditions, the driving wheel motor on the aforesaid side of the vehicle will provide increased torque output to compensate for the reduced driving power of the slipping wheel.

Abstract: A row crop harvester is provided with mechanism for mounting two picking heads for both vertical and horizontal adjustment of the ground engaging lower ends of the heads, to simultaneously harvest two rows of plants which may vary in spacing from each other throughout their lengths. One head is guided along its row by steering the harvester itself, while the lower end of the other head is guided along its row by selectively operating controls which transversely shift the lower end of the head relative to the first mentioned steerable head thereby accurately following and simultaneously harvesting two rows of crops such as root crops.In the preferred embodiment the upper end of each picking head is associated with a severing mechanism for removing the tops or foliage from the roots of the plants.