Abstract: As the tractor and baler are driven straight down the windrow, hay is picked up and placed upon a platform conveyor which transfers the same rearwardly toward the baling chamber, during which transfer a deflector diverts the crop stream into an appropriate one of three axial sections of the chamber as determined by sensing and control mechanism associated with the baler. As the hay builds up in one of the sections, the sensors of the mechanism compare the size of that portion of the bale with the bale portion in the next adjacent chamber section, and once the differential between the two bale portions reaches a certain predetermined level, the control mechanism swings the deflector to its next position, directing hay into that next adjacent section to build up that portion of the bale.