Storing silage in drive-over piles instead of bunkers often results in higher losses. But that doesn't have to be the case, says Kansas State University professor emeritus and silage expert Keith Bolsen.

“I see no reason why a producer with a pile cannot achieve a shrink that's comparable to a producer with a bunker,” says Bolsen, now a silage consultant based in Austin, TX.

While losses in both types of storage can reach 25-30%, they're far lower than that with top management from harvest through feed-out.

“Our target with the producers we work with, whether it's a bunker or pile, is single-digit shrink,” Bolsen states.

Minimizing losses in drive-over piles is “about location, proper sizing, proper shape, sufficient packing to achieve your density targets, a very effective seal, going out there once a week and checking your seal, and it's about good feed-out techniques,” he adds.

Most of those requirements are the producer's responsibility. But when a custom harvester makes a pile, he should work with the producer to predetermine its size and shape. Proper dimensions ensure that the silage can be packed uniformly throughout the pile, and that the daily feed-out rate will be sufficient to prevent deterioration on the face.

To minimize the risk of deterioration, Bolsen recommends that at least 12" of silage be removed daily after feeding begins, regardless of the time of year.

Worker safety is an important consideration when sizing piles, too. According to Bolsen, the pile's highest point, or apex, should be no higher than the maximum reach of the unloading equipment. If the apex is too high, silage near the top of the face will be undercut during feed-out, resulting in an overhang that's a hazard for people working underneath it.

Once pile height is set, the width is determined by the slope of the sides. The maximum recommended slope is 1:3 — a foot of rise for each three horizontal feet. So if the pile is 10' high at the apex, a 1:3 side-slope ratio results in 30' of silage on each side, or a 60'-wide pile.

The 30% maximum slope is crucial, says Bolsen, because steep sides are dangerous for tractor drivers, and the silage doesn't get adequately packed.

“If the ratio gets out of balance, all of a sudden you've got a drive-on pile, not a drive-over pile, and there's a huge difference,” he says. “The sides don't get compacted if you can't drive up and over. And when you seal that drive-on pile, you will have a foot or two of visible spoilage because you couldn't get it compacted.”

Pile ends should have the same slope as the sides so the pile can be driven over from any direction. So be careful to establish the slope as you start the pile, building toward the apex. Then maintain it along the sides and as you finish the pile on the other end.

Piles should be built using the progressive wedge technique, spreading the silage in thin layers and packing each layer, much like bunkers are filled. Don't skimp on packing; it's the most critical step in silage pile management.

Bolsen says to aim for a dry matter density of 15 lbs/cu ft. A spreadsheet developed by ag engineers Brian Holmes, University of Wisconsin, and Richard Muck, U.S. Dairy Forage Research Center, can be used to predict silage densities at various delivery rates, moisture levels, packing tractor weights, etc. It's available at

“It's the most important tool we have in managing bunkers and drive-over piles,” says Bolsen.

Piles should be covered as soon as possible after they're finished. Don't cheat on materials, Bolsen advises. He often recommends two sheets and a new oxygen-barrier film, Silostop, as the sheet that's in contact with the silage. Pull the sheets over the pile and at least 4-6' beyond the edges on the sides and ends. Seal the perimeter with sand, limestone, pea-gravel bags or other material so no air can get underneath the plastic. If tires are used there, they should be touching.

If the plastic isn't big enough to cover the pile and more sheets are needed, overlap them at least 4-6' and put extra weight along the overlap area.

“If you're using truck sidewall disks, put two disks together on the overlap,” Bolsen recommends. “Or if you're using whole truck tires and disks, use whole truck tires on the overlap so there's no way the overlap can split. And then make sure you've got the entire remaining surface uniformly weighted.”

Ideally, each haylage cutting should be stored in a separate pile. That makes it easier for the producer to keep rations consistent. When adding to a previously made pile, you'll be putting one cutting on top of another since pile ends are sloped. If the two cuttings are distinctly different, silage quality may vary daily during feed-out.

“I want each cutting in a separate pile, but that's not always the case,” says Bolsen. “So whenever you remove that seal and start filling again, if there's a significant amount of spoilage on that surface, the spoilage should be removed.

“But chances are, if you did a good job of finishing off that previous cutting, there won't be any spoilage to worry about.”

For more information, go to the Kansas State Silage Team Web site at