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Storing Shelled Corn in Silage Bags
Bill Wilcke,
Minnesota Extension Engineer
Some farmers and grain elevators are considering using
plastic bags that were designed for storing silage for
temporary storage of dry or slightly damp shelled corn. Will
this work? I’m not aware of any controlled research
studies on using plastic bags for dry or damp shelled corn,
but some farmers and elevators are experimenting with this
type of storage. In this article, I’ll give my best
guesses about how silage bags will work for shelled corn and
I’ll share some of the lessons learned by a Minnesota
farmer who filled 15 silage bags with shelled corn last
fall.
The bags that I’m referring to are usually 6- to
9-ft diameter and 50- to 300-ft long. A special machine is
used to pack corn into the bag as the bag is pulled open.
The end of the bag is tied after it is full to create a
nearly airtight environment. What happens to the corn after
the bag is closed depends on the corn moisture and
temperature:
- If the corn is put into the bag at high (25 to 30%)
moisture and the outdoor temperature is relatively warm,
naturally occurring bacteria cause fermentation and the
corn is ensiled. The bacteria consume oxygen and some
corn dry matter and produce carbon dioxide and organic
acids as byproducts. This low oxygen, high carbon
dioxide, acidic environment preserves the crop and
protects it from deterioration by fungi (commonly called
molds). But if the bag is opened either intentionally or
accidentally, oxygen will enter the bag and mold will
grow on the wet corn.
- If the corn is damp (16 to 20% moisture) and the
temperature is warm, bacteria won’t grow (they need
high moisture levels), but fungi (molds) will. Fungi
consume oxygen and produce carbon dioxide, but they
don’t produce the grain preserving acids that
bacteria produce. Presence of fungi on corn kernels
(called mold damage) reduces the corn’s feed value
and commercial value. If the bag remains airtight,
it’s possible that the molds will eventually stop
growing as they reduce oxygen levels and raise carbon
dioxide levels in the bag. We don’t have sufficient
experience yet to know whether there will be enough mold
damage before the oxygen is consumed to cause marketing
or feeding problems. Experiments with bagging and
wrapping of damp hay that is too dry for fermentation
indicates that if you can provide an airtight
environment, you can often prevent mold growth. As with
high-moisture corn, any openings in bags of damp corn
will lead to mold growth.
- If the corn is damp, but the temperature is low,
neither bacteria nor molds will grow very fast. This
means that you can probably store damp corn in bags
through an upper Midwest winter without too much mold
damage. But because the bags are long and narrow, they
have a high surface area to volume ratio and the corn
will quickly warm to outdoor temperature in the spring.
As the corn temperature increases, mold will begin to
grow and it will be necessary to maintain a tight seal to
limit oxygen entry and mold damage. It might be possible
to hold damp, bagged corn into warm weather, but the risk
of spoilage will be fairly high. Again, any openings in
the bag will allow mold growth.
- If the corn is dry, mold growth shouldn’t be
much of a problem in either cold or warm weather.
However, any openings in the bag will allow entry of
stored grain insects and possibly moisture, which can
lead to spoilage problems in warm weather.
Here are some observations from the Minnesota farmer who
tried storing corn in bags last fall. He filled one bag with
approximately 19% moisture corn and unloaded it in March;
the other bags were filled with corn closer to 15% moisture
and they have not been unloaded yet.
- The bags are easy to fill, but difficult to unload.
Use of a vacuum-type grain conveyor was slow and labor
intensive, so the farmer is designing and building his
own machine that features a large-diameter auger to make
unloading faster and easier.
- Rodents (rats, mice, and squirrels) and birds will
create holes in the bags and you must check the bags
frequently and reseal holes immediately to prevent entry
of moisture and oxygen. Bags that were placed near rows
of trees had more damage from animals than bags that were
stored out on open ground.
- Except for some mold growth near holes in the bag,
the 19% moisture corn that was removed in late winter
looked good and flowed well when the bag was emptied. The
corn was sold without any discounts for mold damage.
- There is enough damage to the plastic bags from
rodents and from handling that they can only be used
once. This means that you need to purchase new bags and
find a way to dispose of (and preferably recycle) old
bags every year.
- Although the farmer believes that storing corn in
bags is an economical, temporary storage solution, he
also recognizes that until we gain more experience and
knowledge, storing shelled corn in bags is a high-risk
operation!
Based on corn storage principles and farmer experience,
here are some suggestions for people who are considering
using silage bags for shelled corn storage:
- Dry shelled corn is preferred, but if you store damp
corn, fill bags late in the fall and empty them by
spring.
- Place bags in open areas away from trees and
buildings that might harbor birds and rodents. Also,
protect bags from farm animals, hunters, and snowmobile
riders.
- Check the bags every week and reseal holes
immediately.
Recognize that the risk of spoilage is probably higher
for corn in bags than it is for corn stored in aerated,
metal grain bins.
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