Editing Baler (section)

===Silage or haylage===
[[File:High Moisture Round Bale - Pickup and Wrapping 320k.ogg|thumb|320px|Video: Picking up and applying plastic cling wrap to a round bale.]]
[[File:High Moisture Round Bale - Sealing Bales Together 320k.ogg|thumb|320px|Video: Sealing the wrapped bales together.]]
[[File:In-line bale wrapped hay.webp|thumb|[[Bale wrapper#In-line bale wrapper|In-line bale wrapped]] hay]]
[[Silage]], a fermented animal feed, was introduced in the late 1800s, and can also be stored in a silage or haylage bale, which is a high-moisture bale wrapped in plastic film. These are baled much wetter than hay bales, and are usually smaller than hay bales because the greater moisture content makes them heavier and harder to handle. These bales begin to ferment almost immediately, and the metal bale spear stabbed into the core becomes very warm to the touch from the fermentation process.

Silage or haylage bales may be wrapped by placing them on a rotating bale spear mounted on the rear of a tractor. As the bale spins, a layer of plastic cling film is applied to the exterior of the bale. This roll of plastic is mounted in a sliding shuttle on a steel arm and can move parallel to the bale axis, so the operator does not need to hold up the heavy roll of plastic. The plastic layer extends over the ends of the bale to form a ring of plastic approximately {{convert|12|in|cm}} wide on the ends, with hay exposed in the center.

To stretch the cling-wrap plastic tightly over the bale, the tension is actively adjusted with a knob on the end of the roll, which squeezes the ends of the roll in the shuttle. In the example wrapping video, the operator is attempting to use high tension to get a flat, smooth seal on the right end. However, the tension increases too much and the plastic tears off. The operator recovers by quickly loosening the tension and allows the plastic to feed out halfway around the bale before reapplying the tension to the sheeting.

These bales are placed in a long continuous row, with each wrapped bale pressed firmly against all the other bales in the row before being set down onto the ground. The plastic wrap on the ends of each bale sticks together to seal out air and moisture, protecting the silage from the elements. The end-bales are hand-sealed with strips of cling plastic across the opening.

The airtight seal between each bale permits the row of round bales to ferment as if they were in a [[silo bag]], but they are easier to handle than a silo bag, as they are more robust and compact. The plastic usage is relatively high, and there is no way to reuse the silage-contaminated plastic sheeting, although it can be [[recycling|recycled]] or used as a fuel source via [[incineration]]. The wrapping cost is approximately US$5 per bale.{{Citation needed|date=June 2013}}

An alternative form of wrapping uses the same type of bale placed on a [[bale wrapper]], consisting of pair of rollers on a turntable mounted on the three-point linkage of a tractor. It is then spun about two axes while being wrapped in several layers of cling-wrap plastic film. This covers the ends and sides of the bale in one operation, thus sealing it separately from other bales. The bales are then moved or stacked using a special pincer attachment on the front loader of a tractor, which does not damage the film seal. They can also be moved using a standard bale spike, but this punctures the airtight seal, and the hole in the film must be repaired after each move.

Plastic-wrapped bales must be unwrapped before being fed to livestock to prevent accidental ingestion of the plastic. Like round hay bales, silage bales are usually fed using a ''ring feeder''.