How to manage high-moisture corn in a bunker silo

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Storing high-moisture corn in a bunker silo can be risky business - especially when you're dealing with a crop that's more prone to spoilage than forages.

Just ask Peter Jacquier of East Canaan, Conn. Jacquier has stored high-moisture corn in bunkers for the past seven years. During that time, he's taken extra precautions to reduce spoilage of this valuable crop. As part of his management plan, he covers the bunker with two sheets of plastic, plus tires, to prevent moisture from seeping into the corn.

Don't take chances when storing high-moisture corn in a bunker. Use these points to help you manage it properly.

Size the bunker
The first step toward good management of high-moisture corn in a bunker silo is to size the bunker properly.

Most dairies feed less high-moisture corn than forage, so a bunker which stores high-moisture corn doesn't need to be as wide as a bunker which stores forages, notes Brian Holmes, extension agricultural engineer at the University of Wisconsin. However, the bunker must be wide enough - a minimum of two tractor widths - to accommodate your packing equipment. For example, if your tractor is 8 feet wide, the bunker should be at least 16 feet wide.

Part of the equation to decide the right width for your bunker is density and feedout. Always aim for a dry matter density of 45 pounds per cubic foot for high-moisture shelled corn and a feedout rate of at least 3 to 6 inches per day, advises Kurt Ruppel, dairy specialist with Pioneer Hi-Bred International in Greenwich, N.Y.

In addition, Holmes recommends storing the corn in a bunker with a minimum 8-foot depth. If you don't feed enough corn to meet these recommendations, consider using plastic silage bags instead, he adds (To size a bunker properly, please see, "Size it right" on page 86.).

Harvest properly
Ruppel offers these guidelines to help you get good results when harvesting high-moisture corn:


  • Watch moisture levels
    Keep close tabs on grain dry-down conditions at harvest, as overly-wet corn can result in longer fermentation which increases dry matter loss. Furthermore, if the grain is too dry, excess spoilage and mold growth can occur. To avoid problems, harvest high-moisture corn at 28 percent to 35 percent grain moisture.
  • Use kernel processing
    Use a roller mill or hammer mill to process the corn. Break each corn kernel into three to six pieces and break the cob into cubes which measure 0.25-inches or less.

    Mike Larson, dairy manager with Larson Acres in Evansville, Wis., has stored high-moisture corn in bunkers for three years. During that time, he has used a roller mill to process the corn during ensiling at the bunker. This year, the dairy purchased a hammer mill to process the corn fed to animals on the 950-cow operation.

  • Apply inoculants
    Both Jacquier and Larson apply inoculants to protect the quality of their high-moisture corn. "You need all the safety you can get," Jacquier adds.

    If you plan to use an inoculant, apply it at the chopper or combine, or use it in combination with a hammer mill or roller mill during ensiling at the bunker, Ruppel says. Purchase an inoculant which is designed specifically for high-moisture corn and follow the manufacturer's directions for proper application.


Fill, pack and seal quickly
The same rules that apply to forages apply to high-moisture corn ensiled in a bunker: Fill, pack and cover the bunker rapidly.

When filling the bunker, Holmes suggests that you build a drainage channel to reduce moisture from seeping into the corn. (For a description of this process, please see "Build a drainage channel in your bunker" below.)

Larson Acres plans to take a similar approach when the dairy harvests high-moisture corn this fall. They plan to line the walls with plastic to capture moisture between the walls and the plastic. Furthermore, they will install drainage tile along the inside of the walls and the plastic to carry the captured moisture out of the bunker. Larson says this practice may prevent moisture from running down the walls and into the corn where it has led to increased moisture levels in corn up to 2 feet away from the wall.

When packing is complete, cover the bunker with plastic and tires to reduce air and water penetration. Jacquier, who operates Laurelbrook Farm in East Canaan, Conn., doesn't take any chances - he uses two sheets of plastic, topped with tires, to cover the bunker. Furthermore, he has a tarp system in place to cover the corn if a rain shower occurs during filling.

Take care at feedout
To prevent spoilage at feedout, maintain a smooth face when you remove high-moisture corn from the bunker. To do so, use the loader bucket to shave corn down the face of the bunker, Holmes says.

At a bare minimum, remove 3 inches of corn per day to keep ahead of spoilage. During the summer, bump this amount up to at least 5 to 6 inches per day, Ruppel advises.

Since Laurelbrook Farm is located about 30 miles from the site where Jacquier stores the high-moisture corn, he removes 12 to 16 tons of corn - about 1.5 feet of corn - every other day to feed on the 850-cow operation. Furthermore, he pulls the plastic down and covers the face after each feedout. "We're just out for optimum quality," he adds.

Always clean up loose corn from the floor of the bunker to discourage rodents and prevent problems associated with damp, moldy feed.


Size it right

Use the steps below to help you design a bunker for storing high-moisture corn.

1) Determine daily high-moisture corn needs:
____ lbs. of high-moisture corn (dry matter) fed per day
÷ 1 - (___ % storage and feed loss ÷ 100)
= lbs. of high-moisture corn needed per day
(Use a 15 % storage and handling loss.)

2) Choose the depth and density:
Depth: ____ feet (8 feet is typical.)
Density: ____ lbs. dry matter per cubic foot (Well-packed high-moisture corn averages 45 pounds of dry matter per cubic foot.)

3) Select face removal rate:
_____ feet removed per day (Remove a minimum of 3 to 6 inches per day.)

4) Determine bunker width:
____ pounds of high-moisture corn (dry matter) needed per day
÷ ____ feet removed per day
x ____ depth
x ____ dry matter density
= ____ feet
(Make sure your bunker width can accommodate the width of your packing equipment.)

5) Determine bunker length:
______ feet removed per day
x _____ days you need to store feed
= ___ feet
(Do not exceed a length of 150 feet per bunker.)


Build a drainage channel in your bunker

High-moisture corn is more valuable per ton than forages, so it pays to reduce the amount of moisture which seeps into the corn. One way that you can do this is to build a drainage channel during bunker filling, suggests Brian Holmes, extension agricultural engineer at the University of Wisconsin. Here is Holmes' three-step process for doing so:

Step 1. Use the progressive wedge method which fills the bunker at an angle. Shape the top portion of the wedge into a "V" with the lowest point of the "V" positioned at the center of the bunker. This slopes the corn away from the wall.

Step 2. Fill in the "V" with a mound of high-moisture corn so that the bottom edges of the mound are 3 to 6 feet away from the wall. This creates a drainage channel which directs water off the ends of the bunker, reducing the amount of water which trickles down the wall and into the corn. If possible, slope the channel toward the back of the bunker to prevent water from running into the feed exposed at the face.

Step 3. Cover with plastic and tires. Weigh the edges down with sand bags or loose soil to get a good seal.


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