Optimum corn silage packing density, the benefits of sidewall plastic, safety and bunker and pile height were discussed during a bunker-management producer session at last spring’s Pennsylvania State University Forage Focus seminar.

Producers and moderator Paul Craig, Dauphin County, PA, Extension educator, traded experiences and knowledge during the roundtable talk. Here’s the gist of what they discussed – and want to know more about:

Packing Density. “Can it get to the point where there are diminishing returns?” one producer asked.

Wisconsin researchers recommend 15 lbs/cu ft on a dry-matter basis, said Craig, who has been conducting silage density studies in south-central Pennsylvania. “What we are finding is that there is no one point to give you a ‘real’ number of the whole bunk. Our numbers would show that the center area and the lower levels are the best packed. The outside areas and the top are the least packed. So we sampled 12 points across the face of bunks, four points across three levels of each face and averaged those 12 samples together and were able to give an average for a whole bunk.”

“Can we overpack?” Craig rhetorically asked the group. “I don’t think that we can.” He believes it is possible to spend more money and time than is justified. “What we found is, because the top and the sides are least well-packed, that’s the area that you have to protect.” He advises using sidewall and surface plastic to protect silage in these areas.

Sidewall Plastic. “That is the best thing that we have ever put in a bunker,” said one grower of his experience in lining bunker sides with plastic.

Another mentioned problems when a family member didn’t take time to line walls. “Now the water runs down the side and on the concrete.”

“Water not only makes your silage wet,” Craig said, “but it is moving down through the sides and leaching nutrients. It also is washing out the acids that are preserving your silage. Then we’re leading to more yeast and mold and bacteria losses – just because of that additional water.”

The group discussed the challenges of draining water that collects near the side plastic. One suggested putting pipe along the bunker wall to help, but added that he tapes the pipe ends so they don’t rip the plastic.

The merits of oxygen-limiting plastics were also asked about. Craig talked about products like SiloStop, which provides the thin oxygen-limiting film and a tarp and gravel bags to protect and seal the silage.

“Companies soon found out that farmers really looked at the tarp as an inconvenience. It was just one more thing that we had to do. So then they put that high-quality plastic into regular white-black plastic. It’s kind of a sandwich layer that they sell as well,” the Extension agent said.

Craig added that University of Delaware researchers covered half a bunker with regular black-and-white plastic and half with SiloStop. The SiloStop side didn’t have as much spoilage as the other half.

Holding Down The Plastic. The group discussed the use of tires or tire sidewalls. Some mentioned that the tire sidewalls weren’t always heavy enough to seal the plastic. One grower’s neighbor built a hydraulically controlled machine that uses planter discs to cut the steel off sidewalls. Just three-fourths of a tire is used to hold down plastic and water can easily be dumped off, he said.

Vibrating Rollers. One producer mentioned that he’d experimented with a vibrating roller to help pack silage, and he was deluged with questions. Essentially, he used two articulating tractors to pack bunkers and rented a self-propelled sheepsfoot roller to pack edges and the top.

He was concerned that the vibrations would make a bunker unstable. “You could feel the vibrating part even if you were on the ground,” he said. It did improve density on bunker edges more than in the middle. His total average density after using the roller was 21 lbs/cu ft. The machine weighed 25,000 lbs and could be rented monthly.

Silage Safety. Several farmers told of close calls while shaving pile or bunker faces that seemed safe but collapsed quickly. One told of the death of a worker while pulling samples.

“All three workers went up to the face and they pulled a sample, turned to walk away and the pile just fell away. It hit … two people from the back and knocked them down. The other guy was walking toward the loader and it completely covered him up. We are still having a hard time dealing with that.”
After the accident, the farm developed a safety plan. “Our policy is that nobody is allowed closer to the bunker face than the height of the bunker long. No exceptions. If there is a tire there, we will get it later. If there is a forage sample, you better take it with a bucket. We thought that it wasn’t an issue, just like everybody else thought it wasn’t an issue. Then it happened to us. You don’t know what a bunker face is like.”