There are several options for ensiling and storing forage crops. Each method has advantages and disadvantages, and have widely ranging capital costs. Some types work well in large operations, while others are better suited for small farms. These methods include horizontal methods, vertical methods, and some flexible small-form methods.
Whatever the system, the primary function of an ensiling and storage system is to exclude air during the ensiling process and to prevent air from entering the silage during storage. This ranks highest in importance because eliminating air in the silage will enhance feed quality and reduce spoilage. Slow silo filling, forage that is not chopped finely enough, inadequate packing and allowing air to enter stored silage all allow excess exposure to air and will reduce final quality of the silage.
Horizontal Silos
Horizontal silos are systems where forage is piled low and long rather than high. Typically, the piles don’t exceed 20 feet for safety and practical reasons, though they may be as low as 6 feet. These silos may be placed above or in-ground and are filled and packed with tractors and loaders, so they would ideally be designed to accommodate the size and type of equipment you plan to use for loading and compaction in order to maximize efficiency and speed the loading process. For tractors and front-end loaders, 50 ft is a convenient width, for example.
The main advantage of horizontal silos is their low capital cost. They’re also suitable for feeding livestock in several distant pens simply by placing the silos accordingly.
One common challenge with horizontal silos is sizing them correctly for feedout. If you have a relatively small herd, design your silo for a small face - go for long rather than high or tall. You’ll want to pull at least 6 inches of silage each day, since exposure to air will encourage aerobic bacteria and fungi to begin reproducing, which will rapidly lead to spoilage. If you have an overly large face, then, you’ll waste a lot of silage. In the end, size your silo conservatively. If your feed needs increase, pulling more is always an option, but you’ll rarely get away with pulling less.
Trench silos are three-wall structures dug into the ground which use the walls of the excavation to physically contain the ensilage and maintain compaction. Care should be taken to ensure the walls remain stable and avoid cave-ins. If the soil isn’t stable, line the excavation with reinforced concrete walls. The floor should be slightly sloped towards the open end to encourage drainage. The walls and floor of trench silos must be covered with impermeable plastic liners to prevent contamination as well as to capture and divert leachate or silage effluent and prevent it from soaking into the soil or draining to surface waters.
Bunker silos are above ground structures with constructed sidewalls, usually made of concrete. They may be partially sunk into a trench or completely above ground and the silage is filled and packed using tractors and loaders. Once the bunker is filled, it’s covered with one or more layers of tarp intended to protect the silage from air and light. Feedout can be managed very close to the bunker, but not directly at the bunker face. .
Pile and stack silos are typically just mounded on the ground and covered without any structural walls to keep the silage compacted. Leachate and runoff may be managed with an impermeable liner or a concrete pad with a drainage system. This style of silo is relatively fast and simple to set up, so it’s a convenient solution when there’s an excess of forage to handle or when you need a quick short-term storage solution. Keep in mind that this type of structure is highly vulnerable to extreme weather and contamination, and keeping it reliably sealed from air incursion can be difficult. If you have a choice, it’s probably best to use this type of silo in limited situations and with lower quality forage, reserving your best quality crops for more secure systems.
Advantages and Disadvantages
Horizontal silos are not only capable of holding large capacities, but they are extremely flexible in placement and size. In fact, it’s a relatively easy task to increase storage capacity simply by extending the length at one end. Horizontal silos, as a class, are inexpensive to set up and use, as they don’t require the use of specialized equipment for construction or management. In fact, the flexibility of bunker style silos make them easily adaptable to both small and very large operations.
Vertical Silos
Vertical silos are constructed to be tall, rather than broad. They’re usually cylindrical structures, up to 90 feet in diameter and 275 feet in height, although much smaller silos are also in common use. They can be constructed from a variety of materials, but the high acidity of well-fermented silage requires the use of interior liners to prevent damage to concrete silo walls.
Advantages and Disadvantages
Vertical silos tend to pack and maintain density well due to the weight of forage piled above it. This compaction minimizes storage losses by naturally excluding oxygen which can support the growth of damaging microbes. Vertical silos also have a smaller footprint for the amount of silage they can process, which is a significant advantage when space is at a minimum. Silos are also configured to take advantage of mechanization during filling and feedout, which saves in labor costs.
Vertical silos are more expensive to purchase and install, meaning it takes longer to recoup costs. Vertical silos are also less tolerant of excess moisture in the ensilage, and over time the structures are subject to weakening and collapse in the face of long term degradation from acid exposure. These acids cause deterioration to all types of concrete silos: including cast-in-place (poured), pre-cast, and stave.
Bagged and Baled Silos
A newer system of ensiling involves wrapping wilted forage securely in tightly stretched, airtight plastic to create a mini fermentation silo. There are several significant advantages as well as disadvantages to this type of system and of course there are different methods for wrapping the bales. One option is tube wrapping, which creates the appearance of enormous, long white worms that stretch along your fields, or single bale wrapping (also called individual or one-at-a-time wrapping), which looks very similar to traditional round or square hay bales, often featuring white plastic covers.
Bagged and baled silos are an increasingly popular feed option for many farmers and ranchers, but it’s important to understand the pros and cons of each option. First, the way the silage is wrapped can make a big difference, both in quality and efficiency and you’ll need to find a balance between the two. Tube wrapping can save plastic and reduce plastic waste, for example, but it’s not as flexible in everyday use as single bale wrapping. Single bale wrapping, whether it’s for square or round bales, requires more plastic since each bale must be individually sealed. However, both tubes and individual bags are easily adjusted to fit the amount of silage you’re working with. Whether you have a bumper crop or a lean year, your silage method requires no adjustments.
Overall, silage tubes, bags, and bales require very little infrastructure to use. Usually, a single machine is all that’s needed to fill and compact the tube, bag, or bale, and the bags can be stored directly on the ground, provided it’s free of rocks and other sharp, poky things. If you’re looking for extra durable material, grain bags are an excellent (though slightly more expensive) option.
Tube bags may provide better results than individually bagged or baled silage because the environment is more effectively sealed, but to be cost effective, the tubes need to contain several hundred bales since material at each end of the tube still tends to experience spoilage.
On the other hand, for individually bagged or wrapped bales, the convenience and flexibility can be compelling even though it’s more expensive on a per-piece basis, It’s possible to load individual silage bales on a truck and haul them around the farm to feed livestock in place, and if you have excess, it’s even possible to sell extra silage to neighbors - that’s not possible with traditional ensilage methods. With tube or traditional silo styles, harvesting and ensiling must happen quickly and all at once to minimize spoilage, but individual bale ensiling allows you to slow the process down or even manage several different harvests throughout the season.
Finally, at feeding time, individually baled silage shines. There’s no need to carefully manage the face as in bunker or other traditional silos, since each time you open a bag, it’s completely fresh. Just pop open a bale, load it in a ring feeder, and you’re done.
Advantages and Disadvantages
Bagged, baled, and tubed silage systems are inherently flexible in the volume, harvest timing, and location of silage. Both ensiling and feeding-out processes are highly efficient. If appropriate equipment is available, a single person could manage the steps involved in creating round bale silage, and the system works well for both small and large operations. Storage losses are lower for individually sealed bales, while feed can be inventoried by simply counting bales or tubes. Initial capital investment is lower and there are fewer safety and health hazards associated with these systems.
Since dense compaction is so central to successful fermentation, specialized equipment is necessary to produce high quality silage. Care must be used when placing or moving silage bales, since a compromised bag can result in complete loss of the bale (although, happily, that won’t affect adjacent bales that are still sealed). The use and disposal of large amounts of plastic wrap is also a concern for the environment. Many manufacturers may assert that their product is recyclable, but local infrastructure and markets may not support that type of material.
