Knowing the size of silage cover you need is far from the only decision to make. In fact, it’s often best to choose a silage cover material long before you ever worry about planning out the sizes of your silos and piles. If you can’t secure a reinforced geomembrane to use for both the pad and cover, you may have to redesign your silage plans to compensate for using weaker materials. Avoid becoming overwhelmed by the sheer amount and variety of products available on the market for silage cover. Sort through the options with these hints and tricks to material selection.
Polymers Designed for Safe Feed
Flexible polymers are the primary material used for the various silage covers, whether they’re thin films stretched around individual hay bales or thicker geomembranes used on large piles. Other materials like burlap or canvas simply aren’t impermeable enough to keep oxygen out. While most of the polymers used to make geomembranes and tarps are flexible enough to wrap around lumpy silage piles, they’re not all safe or ideal for this particular use. Compare the materials below to make sure you’re choosing the right one for your next silage cover.
Polyvinyl chloride (PVC) is one of the most popular polymers used for flexible sheets like geomembranes and tarps. It’s commonly used in the silage world in the form of repurposed billboard advertisements transformed into low cost tarps. Unfortunately, most PVC sheets are full of phthalates that aren’t good for the livestock that will eat the silage. There are limited studies on how these chemicals, used to keep the material flexible and soft, affect animals and their growth rates. PVC covers also have shorter lifespans than other materials due to their low UV resistance. Since silage covers are almost always exposed to sunlight for all of its useful lifespan, you’ll want a material with much better UV resistance.
Nylon is the material most commonly used for thin oxygen barriers, but it’s not thick enough or strong enough to serve as a general silage cover. The material is simply too thin and weak to withstand being pulled long distances by hand or heavy machinery. So, it’s often applied as a wrap, with special equipment, to individual bales instead. Nylon is particularly prone to UV breakdown, which is another reason why these wraps aren’t used year after year. If you choose an impermeable silage cover like RPE, you won’t need to apply a layer of nylon oxygen barrier to the silage to get the same effects.
LDPE, HDPE, and RPE
Polyethylene (PE) is a better choice for silage covers than PVC, but not all forms of PE offer the same benefits to the farmer. Reinforced polyethylene (RPE) products, from manufacturers like BTL Liners, is the best option; followed by low density polyethylene (LDPE) and then high density polyethylene (HDPE). RPE offers the best chemical and UV resistance, making it appropriate for use as both the silage pad and cover. BTL’s products are made from a combination of both HDPE and LDPE layers, combining the best of both polymers while reducing the drawbacks of each of them individually.
Woven vs Non-Woven
Inexpensive tarps, in general, are almost all made from woven materials that are a poor choice for silage covers. Woven tarps obviously let a lot of air flow through the gaps between individual strands of material. Even tightly woven materials can only stop so much water and air from seeping through the surface and interfering with the fermentation of the pile. Non-woven, fully impermeable barriers make much better covers for silage piles; even temporarily.
Reinforced vs. Non-Reinforced
As the full name of RPE material suggests above, this kind of polyethylene features a reinforcement layer that increases the cover’s tear and rip resistance. Non-reinforced materials simply can’t compete when being dragged against rough materials over and over again. Limit your use of non-reinforced products to temporary covers for silage in transition. Reinforced covers, preferably made from RPE material, work best for any covers you want to use year after year for ongoing cost savings.
Why Thickness Isn’t the Only Factor
Many farmers make the mistake of only comparing silage tarps and covers by thickness of the material. You’ll find this notated as mils on the marketing or packaging for the tarps. However, the exact material used for the geomembrane, the amount of reinforcement, and the manufacturing method matter more than just the thickness. Thicker materials also tend to crack faster and don’t conform to the surface of the silage pile as well as than thinner ones. RPE is often particularly thin and easy to shape to the surface because it’s tougher than other, thicker materials.
Repurposed vs Purpose Made Silage Covers
It’s popular to try and reuse older tarps and discarded materials to transform silage into feed with as little cost as possible. Many of the farmers turning to silage in the first place don’t have a large budget for ordering special materials and custom fabrication. Materials first used for billboards, athletic fields, or pond liners are often sold for reuse as a silage cover. Unfortunately, these used materials frequently have a surprisingly short lifespan or have existing damage that keeps them from providing true impermeability. They also tend to provide little information on the material composition, making it hard to determine if a particular product is feed safe. Stick to covers designed specifically for hay and silage cover to ensure they’re worth the investment. Thankfully, high quality covers boast years of reliable performance, making the cost worth what you might save on reused alternatives.
Oxygen Barriers vs Covers vs Nets
Many of the films and tarps commonly marketed for silage cover, especially the reused or repurposed materials, are not appropriate to serve as oxygen barriers. They may offer some level of water impermeability, but few qualify as vapor barriers to prevent oxygen exposure and air exchange. Solid, non-woven geomembranes can double as oxygen barriers and general covers thanks to their higher level of water and gas impermeability. Nets are obviously not woven tightly enough to stop oxygen, but they’re designed as extra protection when using thinner barriers, films, and covers. A woven net prevents tearing when weights make contact with a thin cover. If you choose a thicker and more tear resistant silage cover like RPE, you won’t need nets in most cases to complete your system. You still might find them useful in high wind situations or where appropriate cover weighting materials are not so readily available.
Cutting and Seaming Your Own Custom Cover
As with pond liner and greenhouse covering, designing a silage cover with as few seams as possible reduces the work necessary before using it. Custom fabrication allows you to create very large bunker covers that are still cut from a single seamless piece of material. If seams are necessary to fabricate an unusual shape or size, request that this work is done in the manufacturing plant when possible. Factory sealed seams tend to perform better than those crafted on-site with heat welders or adhesives. Since you’ll probably be making and using replacement silage covers for years, it may be worth the effort to invest in your own professional seam sealing equipment eventually. For cover materials like RPE, heat welding techniques tend to last longer and provide more reliable performance than adhesives or chemical welds.
Adding Frames and Anchor Points
In high wind areas and over silos with no retaining walls, cover anchors and frames can be crucial to preventing wind lift. These frames or embedded rings are often fabricated on-site, by an ingenious farmer, who can’t find a commercial solution to their problem. When weighting the cover down isn’t enough to keep it from billowing away during the process, a frame that’s removed at the end is also helpful. Make sure to order pole pockets on some or all of the sides of the custom silage cover so it’s easy to attach to any frame or anchor points without damaging the material.
RPE silage covers are lightweight, tougher than they look, and easy to drag and fold tightly against the surface to keep oxygen out. By controlling both the water and gases that move through the cover material, you’re able to create the precise conditions you need inside the silage pile for rapid fermentation. These durable covers also provide more reliable protection when silage is held for months at a time, especially when conditions outside are difficult. Shop our industry leading selection of RPE cover materials here at BTL Liners.