What Goes into Producing Silage?

The silage production process follows the same basic stages regardless of the specific fermentation and storage method you choose. While different grains and grasses require variations in handling and ideal moisture levels, they all require compaction, proper cover, and regular turning. Very small and low stacked silage piles can be managed by hand, but most substantial silage production will require larger bunkers and tall piles. Some farms may decide to handle certain crops one way and other forage feeds a different way. Determine which style of silage production is right for your farm and what is required for each method.

The 5 Stages of Silage Production

No matter the material used for the silage, the steps of harvesting, fermenting, and using the feed are basically the same. Here’s the basic process for silage production.

1. Harvesting to Oxygen Loss

Once a clover, grass, grain, or forage weed crop is identified as prime for silage use, harvesting and chopping it begins the process. Each material has a specific size recommendation for the chop, with more fibrous materials requiring a finer particle size in general. Plant materials rapidly break down unless moved into a pile and compacted to reduce oxygen exposure as soon as possible. However, many grasses and weed silage crops benefit greatly from wilting in the field for a few hours before compaction. Aim to pack and cover the silage within 12 hours of harvesting or the end of the wilting period, then try to compact the pile enough to achieve oxygen depletion within just a few hours after securing the cover. Exposure to oxygen reduces nutrition and encourages the growth of unwanted microbes.

2. Early Fermentation

As the last of the oxygen is purged from the covered pile, anaerobic bacteria begin their work on the rich sugars in forage feeds. They’ll convert these sugars into acids that preserve the feed, along with byproducts of nitrogen and CO2. The runoff from the pile in this stage can be particularly corrosive and high in fertilizer value. Make sure to use a bottom sealing pad of impermeable geomembrane to control liquid production. The pile’s pH should drop to around 5 during this stage. High moisture and pH levels during this stage result in the infection of clostridial bacteria and other unwanted organisms. The strongest odors and riskiest runoff products are generated at this point. Moving the pile rapidly through this stage is essential for a high nutrient, palatable, feed production.

3. Lactic Acid Production

After you manage to bring the silage pile’s pH level below 5, lactic acid bacteria that is similar to those found in yogurt begin to dominate the mixture. These bacteria get rid of the remaining sugars while stabilizing the nutrient levels and long-term quality of the pile. Low sugar grasses only produce a small amount of lactic acid, therefore generally achieving a shorter storage lifespan than other forages. Smells should begin to lessen as the pH drops. This stage can take anywhere from 72 hours to multiple weeks, depending on the moisture level, inoculations, and heat generation.

4. Stabilized Silage

Silage stabilizes as the sugars are completely depleted throughout the pile. The pH finally stops at 4 to 4.5, depending on the material and wrapping method. It’s possible to hold silage for months to years at this stage by simply keeping oxygen from penetrating the cover. Plant roots and UV degradation can cause tiny penetrations through silage covers, so it’s essential to check and maintain the tarp if you plan to hold silage for long periods.

5. Opening the Pile and Use

Once a mature silage pile is opened permanently for testing, clean up, and feeding, oxygen will obviously enter the mix again. Any yeasts, bacteria, fungi, and mold that were neutralized by the low oxygen conditions start to grow again immediately. This begins the breakdown of the silage as time goes by. Shaping piles so they can stay sealed and then used up with weeks to months will prevent feed quality issues and unnecessary losses to spoilage after opening. Keeping bunkers clean, by sanitizing tractor tires if drive-over access is necessary, will go a long way in maintaining a valuable silage pile. Use at least a foot of silage per day to work your way through a pile before it can spoil. Use this fixed figure to change the height and width of the pile according to the total amount of feed needed.

Speed is of the essence during the harvesting and packing of the silage piles and silos. Once you have tightly covered the entire pile, the silage will mostly take care of itself until it’s mature and ready to use. While mounds are easy to design so they can be tested and checked with minimal oxygen penetration, individually wrapped bales are a little harder to test due to their size and wrapping style.

Pile vs Bale Silage

Large piles of silage aren’t the only option for storing fodder and forage from the fields. Many farmers also wrap individual bales of rolled hay to ferment them into a hybrid feed known as haylage. However, fermenting grasses or clover in individual bales offers a mix of benefits and disadvantages when compared to large consolidated piles.


  • Requires less space and no pad to control leachate
  • Doesn’t involve much testing
  • Possible to store the bales directly in the field where they’ll be used


  • Feed quality is generally lower, due to both small unit fermentation and use of whole cut hay
  • Hard to almost impossible to test the haylage as it develops
  • Wrappers are thin, can’t be reused, are easily punctured, and require special equipment to apply.

Durable silage covers and anchoring weights are essential to all stages of silage development. Don’t try to rely on a thin film that feels like it will tear or blow away as you work with it. Stick with a durable, easy to handle cover material from BTL Liners instead.

Covers by BTL


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