Learn & Understand

The Microbial Fermentation Happening Inside Every Silo

Getting dry matter percentage into the right window before ensiling, as this calculator checks, isn't primarily about moisture for its own sake - it's about creating the precise conditions a specific population of bacteria needs to successfully preserve the forage through fermentation.

What's Actually Happening Chemically Inside a Silo

Once chopped forage is packed tightly and sealed to exclude oxygen, naturally occurring lactic acid bacteria present on the plant material begin fermenting the crop's water-soluble sugars into lactic acid, in a process functioning much like the fermentation that produces sauerkraut or yogurt. This lactic acid accumulation progressively lowers the pH of the ensiled material, and once pH drops low enough (typically into a range where most spoilage organisms cannot survive), the material becomes chemically stable and can be preserved for extended periods without further significant decomposition - as long as oxygen continues to be excluded.

Why the Process Absolutely Requires an Anaerobic (Oxygen-Free) Environment

Lactic acid bacteria performing this fermentation are anaerobic, meaning they function without oxygen present - which is exactly why silage packing emphasizes tight compaction and complete sealing (a proper airtight cover or bag) rather than loose storage. Any significant oxygen infiltration allows competing aerobic spoilage organisms, including molds, to become active instead of the desired lactic acid bacteria, spoiling the forage and potentially introducing the same mycotoxin risks discussed in this category's grain storage guide, rather than achieving the stable, preserved product proper anaerobic fermentation produces.

Why Dry Matter Percentage Specifically Governs Fermentation Success

Moisture content directly affects how this fermentation actually plays out: forage that's too wet (below roughly 30% dry matter, per the calculator page's own reference table) tends to produce excessive seepage and can favor less desirable fermentation pathways (including undesirable clostridial fermentation, producing butyric acid and a distinctly unpleasant, rancid result rather than the intended lactic acid fermentation), while forage that's too dry (above roughly 40% dry matter) is difficult to pack tightly enough to fully exclude oxygen, leaving pockets vulnerable to mold growth even with an otherwise proper sealing process. The 30-40% dry matter window cited on the calculator page represents the range where compaction is achievable and the correct lactic-acid-dominant fermentation pathway is most reliably favored.

Applying This to a Calculated Dry Matter Result

A dry matter percentage within the ideal range isn't just a moisture target for its own sake - it's the precondition for the specific anaerobic lactic acid fermentation process that actually preserves the forage, and pairing a correct dry matter percentage with genuinely thorough packing and sealing to exclude oxygen is what allows that biological process to run to completion successfully rather than being disrupted partway through by competing, spoilage-favoring organisms.