A baler is described for forming square bales made up of several separately tied slices. The baler has a bale chamber 26 and a plurality of needles 42 movable in unison through the bale chamber 26 to pass respective strands of twine from one side of the bale chamber 26 to associated knotters 40 located on the opposite side of the bale chamber 26. A first set of permanently operative knotters 40 knot strands of twine tied around individual slices on each occasion that the needles 42 are moved through the bale chamber 26. A second set of knotters 40, capable of being selectively disabled by movement of a frame 80 carrying their twine engaging components to a position out of reach of the tip of the needles 42, knot the remaining strands of twine only at the end of the formation of a complete bale.
