But they must be made and managed well, because piles typically have higher spoilage losses than other storage methods – 18% vs. 15% for bunkers and 10% from bags or stave silos.
The flexibility of piles is appealing to dairymen; pile capacity can vary and silage can be easily separated by quality. Yet piles take up a lot of space, require a lot of plastic and tires, need more labor and expose a larger area to potential damage.
“There is a little more vulnerability than you might have with a bunker silo,” Muck admits.
But piles shouldn’t just be built, they should be planned, he adds. To do so, first figure out how much silage you expect to feed out – pounds per day per animal times number of animals.
“Then you want to match the unloading equipment with the height of the pile. You don’t want to be in that situation where the bucket only goes up to 10’ and you have 20’ of material.”
Also figure out how long you expect to feed out of the pile and the number of inches expected to be taken off the face.
Most experts recommend a 6”/day feed-out rate. But Brian Holmes, a University of Wisconsin ag engineer, advises a rate of 12” so, if anything happens to reduce that rate, you will still be able to take a reasonable amount off the face without causing excessive spoilage.
Watch the angle of side slopes, Muck warns. “There is a tendency to create fairly steep slopes, and that creates problems from a safety issue when packing and in doing a good job packing. It creates a problem in sealing, because if you have too steep of sides, it’s hard to keep the plastic against the side walls.”
A fairly gradual slope of 1’ or less rise for each 3’ horizontally will create a good packing situation, he says.
The University of Wisconsin Team Forage’s silage pile sizing calculator, found under the “Bunker and Pile Silo” heading, can help you develop pile dimensions, Muck says. “Typically, we would recommend something that is 150-200’ long. But, obviously, that depends on the size of the operation.
“The bottom line in planning is that you want to create a face that really fits with the number of animals that you are feeding.”
Packing silage piles at higher densities means lower storage losses, he adds. “We have been recommending a minimum goal of 15 lbs of dry matter/cubic foot. And now we are starting to look more at the as-fed density and looking at the minimum density of about 44 lbs as fed.”
A survey done 10 years ago reported three key factors to providing well-packed piles: The crop needs to initially be spread in thin layers, pack-tractor weights must be sufficient and enough time per ton must be spent packing.
When forage was harvested at 60 tons/hour and packed at 1 minute/ton, Muck says, those factors could be maintained. Today, however, forage harvesters are increasing in horsepower and packing density is often lower.
“If I bring 180 tons/hour into that bunker or pile and don’t change my packing practices, I am now spending a third of a minute – 20 seconds/ton – packing that same amount of material.
“So how can I address that situation? Well, I can make my tractor heavier within company specs. Another way is to have three tractors in order to handle that capacity. It’s not just the number of tractors, but the type (and weight),” he adds.
“When you put multiple tractors on a pile, you want to have them fairly uniform in weight. If there are big discrepancies in the weights of those machines, the light one is not going to create extra density.”
Muck recommends that growers use a silage pile density calculator spreadsheet (found under the heading “Silage Storage Type, Sizing, and Management”) to determine what it takes to obtain good packing density with which type of machinery.
He also recommends using experienced operators who can pack continuously and drive slowly to avoid wheel slip, which will kick up rather than pack silage.
“And on a pile, we have that advantage to have coverage in both directions – not only going front to back but also side to side.”
By covering piles immediately after ensiling, losses could stay at just 10%, according to a study by Keith Bolsen, a silage consultant and retired Kansas State University forage management specialist.
Muck recommends heavier white plastic, held securely with tires or sand to keep air out. He has also studied the oxygen-barrier film called SiloStop, which can improve dry matter recovery. (Visit hayandforage.com and search for SiloStop to learn more about his research.)
“But the issue is really how well the plastic is secured to the crop. You can have the best plastic in the world, but if it isn’t secured well, then you are going to run into spoilage issues.”
Editor’s Note: Mentions of trade names or commercial products in this report are solely to provide specific information and do not imply recommendation or endorsement by USDA.