Abstract: A processor for processing standing plants has a primary crop sub-system for processing upper parts of the standing plants and a secondary crop sub-system for processing lower parts of the standing plants, the primary and secondary crop sub-systems operable to process the respective upper and lower parts of the standing plants as the processor moves through a stand of the standing plants. The processor, as part of a field located vehicle, is operated to separate a primary crop such as corn cobs or grain from the standing plant at a first processor zone, and to separate a secondary crop suitable for bio-fuel processing from the standing plant at a second processor zone. Settings of the primary and secondary crop sub-systems can be made adjustable so that the relative lengths of upper, lower and root parts of the standing plants can be adjusted as desired.