Dry matter recovery at the tops of bunkers and near bunker walls can be improved by as much as 15 percentage units if oxygen-barrier films are used to cover stored silage, says Rich Muck, a U.S. Dairy Forage Research Center researcher in Madison, WI.

But traditional white plastic tarps held down by tires can do a good job, too, he says.

Muck has studied Silostop, a silage-covering system, for more than five years and says the product works well. But white plastic, put down bunker sidewalls and brought over the top, can keep air out, too.

Good-quality plastic and a tight seal make both methods successful, he adds.

The two-step Silostop system, manufactured by Bruno Rimini Corp., uses a clear polyethylene plastic film treated to keep oxygen from silage. Only about 1.8-mil thick, the film is spread down bunker sidewalls and overlapped at the top once silage is packed. A woven, plastic reusable tarp is placed on top of the overlapped film and held in place by 3’ bags filled with pea gravel. Muck has completed several studies of that system.

Compared with the traditional 6- to 8-mil white polyethylene plastic secured with tires, Silostop recovered 17 percentage units more alfalfa dry matter and 13 percentage units more corn silage within the top 6” and about 2’ from bunker walls, Muck reports.

The woven-mesh tarp provides ultraviolet protection, is strong enough to resist damage from rodents and other animals and “really helps to hold the plastic film tightly against the crop. I would say it does a better job than tires do in terms of providing a good seal.”

The tarps, however, cost twice that of traditional silage coverings and have to be reused for about five years to justify the system’s cost. They hold up, but aren’t as convenient as throw-away coverings.

That’s led Bruno Rimini Corp. to produce a one-step plastic film, which Muck is also studying. “We didn’t see any benefit in terms of improved quality,” he says, because the plastic was held just by gravel bags that couldn't hold it tightly against the crop.

Muck just started a second study of a new formulation of the one-step film, using gravel bags and tire sidewalls to help hold film in place. “Then we have another treatment where we’re using a mesh material to help hold the film in place.” Those treatments will be compared to bunkers covered with the traditional covering method and with Silostop’s two-step system.

All four treatments will include plastic laid down the sides of bunker walls, he says. “If there’s anything that has come out of this research, it’s that the film down the walls is a tremendous benefit in terms of keeping water out of silage and keeping spoilage down.”