A bale wrapper is a farm implement for wrapping bales in plastic, for them to turn into silage.

The wrapper has a loading arm, much like a bale handler, at the side, that scoops up a bale and places it on the wrapping table. The wrapping table usually consists of two rollers, and four belts which slowly spin the bales while the table itself revolves. As the bale turns, plastic film is pulled through the dispensing unit and wrapped tightly on the bale. When the table has revolved at least 16 times, the bale can be ejected. This is done by a hydraulic ram which tilts the wrapping table, so that the bale can be tipped off. The film is cut and then tied to the wrapper for the next bale. All this is controlled via a computer inside the cab of the tractor.

http://en.wikipedia.org/wiki/Bale_wrapper