Good silage starts long before the baler rolls into the paddock, but it can be undone in a matter of days if the wrap is wrong. Get it right and you lock in quality feed that holds its energy and protein for months. Get it wrong and you are feeding out mould, waste and disappointment. This guide walks through what silage wrap actually does, the main types on the market, how many layers you really need, and how to store it so your feed is still there when you need it.
Silage keeps because it ferments, and fermentation only works without oxygen. When you wrap a bale or seal a pit, you are shutting the air out so lactic acid bacteria can go to work, pickling the forage and dropping the pH to a point where spoilage organisms cannot survive.
The wrap is the barrier that makes all of that possible. Any oxygen that sneaks back in, through a hole, a poor seal or too few layers, gives mould and yeast the opening they need. That is why the quality of your wrap and the care you take applying it matter just as much as the crop you cut.
Bale wrap film is the stretch film you apply with a bale wrapper, most commonly in 750mm or 500mm widths. It is what most Australian producers use for round and square bale silage. It is UV stabilised to handle our sun and comes in white, green and black, which we will come back to below.
Pit and bunker covers are the heavier plastic sheets used to seal silage stored in pits, bunkers or stacks rather than bales. These are thicker than bale film and are often paired with a thin oxygen barrier film underneath for a better seal. They are held down with tyres, gravel bags or silage mats so the wind cannot lift them.
Silage tarps cover open stacks and pits where a full bunker cover is not practical. They are a practical option for smaller operations or short-term storage, though they will not seal as tightly as a purpose-made bunker cover.
Which one you need comes down to how you store your silage. Baled silage needs bale film. Pits and bunkers need covers and, ideally, an oxygen barrier layer.
This is where a lot of spoilage starts. The layer count is not a place to save money.
As a rule of thumb, four layers is the practical minimum for silage you plan to feed out within a few months. Step up to six layers for feed you want to hold longer, for higher dry matter bales, or for stemmy legume crops like lucerne that are more likely to punch through the film. For high-value silage or storage beyond about eight months, some producers go to eight layers.
Keep in mind that layers and wrapper rotations are not the same thing. With 750mm film at the standard overlap, each rotation lays down two layers, so four layers means two full passes and six layers means three. Check your wrapper is set for the overlap the film is designed for, because a stretched or gappy overlap quietly cuts your real layer count.
Thickness is measured in microns. Most quality bale films run around 25 microns per layer, so four layers gives you roughly 100 microns of protection and six gives you 150. Thicker is more forgiving of the odd knock, but layers matter more than any single figure.
Pre-stretch is how far the film stretches as it goes on, usually somewhere between 55 and 70 per cent. Good film stretches consistently without tearing, which gives you an even, clingy seal. Cheap film that stretches unevenly leaves weak points.
Colour matters more here than most people expect. In the Australian heat, lighter colours like white and light green reflect sunlight and keep the bale cooler underneath, which protects the fermentation. Black film absorbs heat and can push temperatures up inside the bale in summer. Unless you have a specific reason to use it, a lighter film is the safer choice in most of the country.
Exact usage depends on your bale size, film width and overlap, so treat any figure as a starting point and confirm against the roll specification and your wrapper settings. As a rough guide, a standard roll of 750mm bale film will wrap somewhere in the range of 25 to 30 average round bales at four layers. Heavier wrapping, bigger bales or more layers will bring that number down, so it always pays to order a little more than the bare minimum rather than run short mid-job.
The wrap does its job, but where and how you store the bales decides whether it lasts.
Pick a clean, well-drained site away from trees, fence lines and stubble that can puncture the film. Move bales as little as possible once wrapped, and handle them with proper bale forks rather than spikes that pierce the plastic. Stack round bales on their ends where you can, as this puts the strongest part of the wrap on top.
Birds and vermin are the quiet destroyers. Crows and cockatoos will peck holes out of curiosity, and rodents chew in from ground level, so keep the area tidy and check your bales regularly. When you do find a hole, patch it with UV-stable silage tape straight away, ideally within a day, before oxygen has time to spoil the feed around it.
Most silage failures trace back to a short list of causes. Too few layers, poor overlap and small holes let oxygen in and let mould take hold. Storing bales too long for the number of layers applied leads to slow spoilage from the outside in. Heat build-up under dark film in summer degrades quality. Rough handling and untidy storage sites cause the punctures that start it all.
None of these are hard to avoid. Wrap with enough layers, use quality UV-stabilised film, store on a clean site, and check and patch your bales through the season. That is the whole game.
You can browse silage wrap, bale film, pit and bunker covers and silage tarps in ourfarm inputs section, where you can compare options from sellers around the country and get your order sorted well before cutting starts. As always, get in early. The best time to sort your wrap is before the crop is ready, not the day the baler arrives.
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