<p>Method and apparatus for separating fibers from a stack of fibrous sheets, either in roll or bale form, by directing the stack of sheets into engagement with a fiberizing means employs a differential feed system for directing the bottom sheet, or sheets, of the stack into engagement with the fiberizing means at a different speed relative to other sheets of the stack. Preferably the bottom sheet of the stack is fed into the fiberizing means at a slower speed relative to other sheets of the stack to minimize clump generation in the fiberizing operation.</p>