Plastic isn't just the last thing Bill Rowekamp deals with when filling bunker silos. It's also the first. That's because he lines his empty bunkers with it.
Two rolls of plastic, each 150' long and 60' wide, are hung 14' down the walls and anchored on the floor of an empty 40 × 90' bunker. Rowekamp fills and packs the bunker, then pulls the remaining plastic over the top from both sides — effectively “bagging” his haylage or corn silage.
Although he spends at least $720 on plastic per bunker, Rowekamp, Lewiston, MN, figures he's saving $3,400 in feed that would spoil using the traditional plastic-over-the-top method. It's also helped increase his herd's milk production and improved its health, he says.
“Since we have been covering this way, we have virtually no spoilage, no molds or toxins,” he says.
But Rowekamp is quick to give credit to former employee Gert Mogensen, originally from Denmark.
“This is the way they had covered their bunkers over there for years,” Rowekamp says. “He said we Americans buy the best seed we can, prepare the fields with tillage and fertilizer, protect the crop as it's growing, then cut it at the right time and, to maximize feed value, get it to the bunker as quick as we can and pack it as best we can.
“Covering the bunker is the last thing, and that's the thing we screw up on,” he remembers Mogensen telling him.
Rowekamp says two plastic top layers keep birds, dogs and rodents from breaking through.
“When we cover the bunkers and put tires on top, we like the guys to have soft-soled shoes on, or sometimes they go barefoot,” he says. “With one sheet, if you get a hole in it, you got a hole. With two sheets, it just gives that bottom sheet a little more protection.”
Throughout the nine years he's used this method, Rowekamp has made refinements and found ways to ease the work. He ground down sharp edges on the bunkers and added quarter pieces of tire to the corners of each to keep the plastic from being punctured. He also made a bar attachment for his loader that holds these 400-lb rolls of 5-mil plastic, making it easier to unroll them.
In recent years, he has placed 4” drain tile along the two sidewalls to allow excess moisture to run from the gently sloping bunker floor.
Four people are then needed to place the plastic, he adds. “It always seems like Mother Nature knows right when we need to work with the plastic, because the wind will pick up. I've seen it pick up 200-lb guys; it's like a big sail.
“So the earlier in the morning we can get it done, the less work — it's the calmest part of the day,” says Rowekamp, who raises 200 acres of alfalfa and 300 of corn, all fed to 640 cows on two farms.
He uses corn silage to hold the plastic to the bunker floor. After the bunker is filled, he packs for another hour “to squeeze as much air out of it as I can.” The past few years, he has been placing an oxygen-barrier sheet over the top of each filled bunker to help seal and protect the silage. Then he covers that with the plastic left hanging over wall edges. Workers then start placing tires.
“It's amazing how fast it starts to ferment. We put the plastic on within two hours after we get done chopping. And as we put tires on and move from one end to the other, we force gas to one end,” he says.
He cuts a hole in both layers to release the gas and then tapes up the openings. Sand is dumped at the ends of the bunker to hold the plastic. “Some people use sand bags. We use sand for bedding, so we have sand around.”
Although the covering method costs more in plastic, it only involves about an hour's work for four people, Rowekamp says. “And it's protecting $45,000 worth of feed.”
Take a couple of minutes to view two producers’ methods to cut silage losses and make more profit.