Corn is a staple energy source for livestock. It stores well, is produced at scale, combines easily with other ingredients, and yellow varieties supply useful carotene. Its main weakness is protein, at only around 8 to 9% crude protein, which is why corn-based rations are always paired with a protein source such as a legume.
But there is a second corn resource that many farms overlook: the crop residue left behind after the grain is taken. Stalks, leaves, husks, and cobs, collectively called corn stover, are produced in enormous volume at harvest and often go to waste. Corn fermentation is how that residue becomes usable feed. This guide covers how it works, and clears up a common and costly confusion about what “fermentation” actually means in this context.
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The Problem With Corn Stover
Corn crop residue is abundant, cheap, and readily available. Almost every part of the plant can be fed. In regions where grass production falls short, corn stover is one of the most promising forage substitutes available.
Two problems stand in the way.
The first is timing. Stover appears all at once at harvest, in a volume no herd can consume immediately, while livestock need feed every single day of the year. Without preservation, most of that abundance is wasted.
The second is digestibility. Corn stover is high in crude fiber and lignin. Lignin is the structural compound that makes stalks rigid, and rumen microbes cannot break it down. The older and drier the plant material, the more lignin it contains, and the less of the feed value the animal can actually extract. Freshly harvested green material is far more digestible than dry, mature stover.
Both problems have solutions, and they are different solutions. This is where the confusion usually starts.
Two Different Processes, Often Confused
The word “fermentation” gets applied to two completely distinct techniques for handling corn residue. Mixing them up can ruin a silo.
| Ensiling (Silage) | Fungal Pretreatment | |
|---|---|---|
| Purpose | Preserve the feed so it keeps for months | Break down lignin so the feed digests better |
| Conditions | Anaerobic, completely airtight | Aerobic, requires oxygen |
| Organism | Lactic acid bacteria | White rot fungi, Trichoderma species |
| Duration | 21 to 30 days minimum | 10 to 30 days under controlled conditions |
| Fungi present? | A sign of failure and spoilage | The active agent of the process |
| On-farm use | Standard, proven, widely practised | Mostly research and specialist systems |
“This is one we get asked about more than people might expect. Someone reads that fungi improve the digestibility of crop residue, and they wonder whether to add fungi to the silo. The answer is no, emphatically. In a silo, fungi mean the seal has failed and you are losing feed. The fungal work on lignin is real science, but it is an entirely separate aerobic process. Ensiling and fungal pretreatment are opposites: one excludes oxygen, the other depends on it.”
— Sue Su, Marketing Director of Silopak
Ensiling Corn Stover: The Practical Method
For almost every working farm, ensiling is the answer to the corn stover problem. It preserves the residue so it can be fed year-round, and it is proven, cheap, and straightforward.
Get the moisture right
Target around 60 to 70% moisture. This is where corn stover differs sharply from whole-plant corn silage, and where a lot of guidance goes wrong.
After grain harvest, stover is often already too dry to ensile well, sometimes well above 50% dry matter. In that case, the problem is not drying it further, it is adding moisture back so the material can compact and ferment. If you are ensiling greener material harvested before full grain maturity, the reverse may apply and a short wilt helps. Assess the material you actually have rather than assuming.
Chop finely
Cut the stalks and leaves into short lengths. Finer material compacts better, expelling the air that fermentation cannot tolerate, and it is easier for cattle to eat and digest. Long, coarse stover traps air pockets and packs poorly.
Pack and seal airtight
Compact the material as tightly as possible into a bunker silo or airtight bags, then seal completely. Lactic acid bacteria only work without oxygen. Any air left inside, or leaking in through a damaged seal, allows spoilage organisms including the very fungi you want nowhere near your silo.
Wait properly
Fermentation needs a minimum of 21 to 30 days to complete. Opening the silo after three or four days does not give you silage; it gives you partially fermented material that has not stabilized and will spoil. Patience here is not optional.
Consider molasses for low-sugar material
Corn stover is lower in sugar than whole-plant corn. Adding molasses gives the lactic acid bacteria the fermentable substrate they need to drive the pH down properly, and it improves palatability, giving the finished silage a slightly sweet aroma.
Reading the Result
Well-fermented corn stover silage has a mildly sour smell, reflecting the low pH of around 4 that fermentation produces. The color shifts to a light brown, because the acids break down chlorophyll and the green fades out of the leaves. It should not be slimy, should carry no rancid or putrid odor, and should show no visible mold.
If it does show mold, air got in. If it smells rancid, the fermentation failed and clostridia took over, usually because the material was too wet or the seal was inadequate.
What About Fungal Pretreatment?
For completeness, the fungal approach is genuine science, and worth understanding even though it is not standard farm practice.
White rot fungi, including species such as Ceriporiopsis subvermispora and Irpex lacteus, secrete enzymes that degrade lignin, the compound that locks up the digestibility of stover. Research has shown lignin degradation of 20% or more over 30 days of controlled cultivation, with substantial gains in how much of the material rumen microbes can actually use. Cellulolytic fungi such as Trichoderma are studied in the same context.
The honest assessment for a working farm is this: fungal pretreatment requires aerobic conditions, controlled cultivation, and careful management, and it remains largely a research and specialist technique rather than routine practice. It is not something to attempt inside a sealed silo, and it is not a substitute for ensiling. If your goal is to preserve corn stover and feed it through the year, ensiling is the method that works.
Protecting the Fermentation
Everything above depends on the seal holding. An airtight barrier is what separates preservation from spoilage, and with corn stover, which is often drier and harder to pack than whole-plant corn, there is less margin for error.
Silopak has manufactured silage film since 2011 from virgin LLDPE, engineered to resist tearing and UV degradation across months of outdoor storage. The film is not an accessory to the fermentation. It is the condition that makes the fermentation possible.
Frequently Asked Questions
Q: Should I add fungi to my corn silage to improve digestibility?
No. Fungi in a silo indicate spoilage, not improvement. Ensiling is an anaerobic process driven by lactic acid bacteria, and it depends on excluding oxygen completely. Fungi require oxygen, so their presence in your silage means the seal has failed and feed is being lost. The research on fungal breakdown of lignin is legitimate, but it describes a separate aerobic pretreatment process carried out under controlled conditions, not something you add to a sealed silo.
Q: How long does corn stover need to ferment?
A minimum of 21 to 30 days. Some guidance suggests three or four days, but that is far too short. After a few days the fermentation is still in progress, the pH has not fallen far enough to stabilize the material, and the feed will spoil once opened. Allow the full period before opening the silo.
Q: Is corn stover too dry to ensile?
It often is, straight after grain harvest. Mature stover can be well above 50% dry matter, which is too dry to compact properly and too dry for good fermentation. In that situation you need to add moisture rather than remove it, aiming for roughly 60 to 70% moisture. This is the opposite of what you do with wet grass, and it is why generic advice about wilting before ensiling can lead people badly astray with stover.
Q: Why is corn stover harder to digest than whole-plant corn silage?
Because of lignin. Corn stover is what remains after the grain has been removed, so it is mostly stalk, leaf, and cob, all of which are structural tissue high in lignin and crude fiber. Rumen microbes cannot break lignin down, so it limits how much energy the animal can extract. Whole-plant corn silage includes the grain, which contributes highly digestible starch, giving a far higher energy value overall. Stover is a fiber and bulk source, not an energy feed, and should be supplemented accordingly.
Reviewed by Sue Su, Marketing Director of Silopak, on 27 July 2026. This guide has been revised to clearly separate anaerobic ensiling from aerobic fungal pretreatment, two processes that are frequently and harmfully confused.
