A baler for agricultural material including a reciprocating plunger that compresses crop material in a channel into flakes which are stacked to provide a bale length of the desired size. The baler is towed from and powered by a steerable tractor having an operator display. The channel receiving the plunger has right and left walls which support star wheels having points projecting into the channel for the flakes and bale. The relative movement of the bale from right to left is determined and indicated to the operator of the vehicle to steer right, left or straight to ensure that bales have thickness that is uniform across their width.
