Making good silage with EM Silage: fermentation, dosage, and best practices

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Ensiling lets you preserve grass, corn, or small grains harvested wet for months by fermenting them without air. Done well, it produces a stable, palatable forage. Done badly, it heats up, gets moldy, loses some of its value, and can even become dangerous for livestock.

Biological preservatives, or inoculants, help fermentation get off to a fast start and head in the right direction. EM Silage is one of them, with a distinctive feature: it combines lactic acid bacteria and yeasts. Here is how to use it, what the research says, and why good harvesting and packing practices remain, by far, the deciding factor.

The principle: lactic fermentation and a falling pH

A silo goes through several phases. Right after filling, there is still air between the stems: the plant cells keep respiring and microorganisms consume sugars, giving off heat. This phase should be as short as possible, ideally less than 24 hours.

Once the oxygen is used up, lactic acid bacteria take over. They convert the sugars in the forage into lactic acid, and the pH drops. This fermentation lasts about two weeks. The usual pH targets are 3.8 to 4.2 for corn, below 4.5 for grasses, and below 4 for legumes. At this stage, the silo remains stable as long as it stays airtight.

The danger returns when the silo is opened. Once air gets in, wild yeasts start consuming the lactic acid, the pH rises, molds take hold, and the forage heats up. Losses can reach 8 to 9% of dry matter per week for a temperature rise of 9 °F (5 °C).

Did you know?

Kitchen bokashi is based on the same idea as silage: an airless lactic fermentation that acidifies the material and preserves it. What the livestock farmer does with tons of forage, the gardener does with a bucket of bokashi.

Why add an inoculant?

Forage naturally carries lactic acid bacteria, but not always in sufficient numbers, nor always the most effective ones. An inoculant supplies a large population right from the start. There are two main families:

• homofermentative bacteria, which produce almost exclusively lactic acid: the pH drops quickly and losses in the silo are reduced;
• heterofermentative bacteria, which also produce acetic acid: this inhibits yeasts and improves the forage's aerobic stability after opening.

The effect of lactic inoculants is well documented. In a laboratory trial published in 2013 on grass and corn, the final pH of the grass went from 4.55 without inoculant to 3.89–4.15 with it, and dry matter losses from 6.3% to 4.0–5.8%. The untreated grass silage began to heat after 96 hours of exposure to air, compared with 162 hours or more for the inoculated batches. Note: this trial involved conventional lactic inoculants, not an EM product.

An inoculant is most useful when conditions are difficult: grass that is too wet, legumes (alfalfa, clover), which acidify more slowly, or corn that tends to heat at feed-out.

EM Silage: composition and dosage

According to the manufacturer, EM Silage is a live liquid made up of homofermentative and heterofermentative lactic acid bacteria and cultured yeasts. It is intended for grass, corn, small grain and legume mixtures, immature small grains, and high-moisture grain. The instructions do not specify the strains.

The presence of yeasts is unusual: in a silo, it is precisely wild yeasts that trigger heating once it is opened. The manufacturer claims that its cultured yeasts take the place of undesirable yeasts and that the acetic acid produced by its bacteria reinforces this effect. We have not found any independent study that confirms this.

Dosage

The manufacturer's current instructions call for 2.7 fl oz (80 ml) of EM Silage per metric ton of fresh forage, diluted in at least 1.1 gallons (4 liters) of water per metric ton to spread the product evenly. For very dry forage, above 45% dry matter, more liquid is needed: at least 4.3 gallons per acre (40 liters per hectare). A 5.3-gallon (20-liter) bag-in-box therefore treats about 275 tons (250 metric tons). The product keeps for one year in its packaging. Always check the dosage on the label of your batch.

Application

• Dilute in unchlorinated water, which protects the live microorganisms.
• Apply evenly at harvest: with an applicator on the forage harvester or by spraying each layer of forage as it goes into the silo.

Emy's tip

Mix the solution on the morning of harvest, in the amount calculated for the day, and keep the tank in the shade. A mix of live microorganisms heating up in the sun in the sprayer loses some of its benefit.

Pack, cover, wait

No inoculant can make up for a poorly managed harvest and packing job. The key points:

• Harvest at the right dry matter content: around 30 to 35% for corn; for grass, at least 30%, ideally 35 to 40%, after a quick 24- to 48-hour wilt. Above 45%, packing becomes difficult.
• Mow at 2.8 in (7 cm) or higher to avoid picking up soil, a source of poor fermentation.
• Chop short, and the drier the forage, the finer the chop: it packs better.
• Pack in thin layers, 11.8 in (30 cm) at most, continuously throughout filling.
• Seal quickly: less than 24 hours between the start of filling and covering, with a thin film in contact with the forage, a heavy plastic cover on top, and carefully placed weights.
• Wait until fermentation is complete, at least two weeks, before opening.

Stability once the silo is opened

Once the silo is open, the rule is to move forward quickly enough that air does not have time to heat the silage face: at least 3.9 in (10 cm) a day in winter and 7.9 in (20 cm) in summer.

• Cut cleanly, without tearing, to keep a smooth, compact face.
• Don't leave loose silage lying at the foot of the silo.
• Check regularly that the face is not heating and does not smell moldy or strongly of vinegar.
• Discard any moldy parts: moldy or poorly fermented silage can make animals sick.

For the mixed ration itself, the manufacturer also offers Organofresh EM, to be added to the mixer wagon at a rate of 1.1 to 2.1 quarts (1 to 2 liters) per metric ton of ration, according to the manufacturer. It aims to limit heating of the ration between mixing and feeding.

What the research says about EM and silage

Silage is one of the uses where an effect of EM is considered plausible, since it is precisely a lactic fermentation. However, data specific to EM products remain limited:

• A trial commissioned by the manufacturer and carried out in 2015 on an experimental farm, on grass wilted to 33% dry matter at a rate of 2.7 fl oz (80 ml) per metric ton, showed no difference in pH, ammonia nitrogen, or yeasts and molds. Aerobic stability and protein content, on the other hand, were significantly better than in the control batch.
• Older trials, reported in the farm press, gave mixed results: a lower pH and silage that stayed stable longer after opening in some cases; elsewhere, with a similar product, an effect that depended on dry matter: unfavorable on very wet grass at 26%, favorable at 30%, and nil at 34%.
• Silage specialists have regretted that the exact composition of EM is not published, which makes it impossible to compare these products with conventional inoculants.

Key takeaways

The benefits of lactic inoculants are established; those of EM Silage rest on a handful of trials, one of them commissioned by the manufacturer. In any case, an inoculant improves a well-run harvest: it will not rescue forage that is too wet, poorly packed, or badly covered.

To understand the role of the different microorganisms in fermentation, see our guide how EM works, and for an overview of the evidence, our guide what science says about EM. EM-fermented feeds given directly to ruminants are covered in our guide fermented feeds for horses and livestock.

In summary

Good silage depends on a rapid lactic fermentation without air, followed by a feed-out rate fast enough to prevent heating. Lactic inoculants help lower the pH, limit losses, and improve aerobic stability: this is well established. EM Silage combines lactic acid bacteria and yeasts, is dosed according to the current instructions at 2.7 fl oz (80 ml) per metric ton diluted in at least 1.1 gallons (4 liters) of water, and is applied evenly at harvest. The available trials on this product are encouraging for aerobic stability but few in number. Harvesting at the right dry matter content, packing, prompt covering, and a steady advance of the silage face remain the keys.

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