Silage in bags is something many farmers overlook because it’s perhaps neither one thing or another. Silage bags don’t quite offer the ease and scale of clamps but at the same time they are not quite so handy as bales. But maybe this middle ground is a good balance, maybe silage in bags (or should that be silage sausages) offers the best of both worlds, the flexibility of bales without the building cost of clamps?

Is there a place for bagged silage?

For many, bagged silage is something to consider when the clamps are all full and there is nowhere else to put that 4th cut. A silage sausage is easier to incorporate into a clamp system than hundreds of bales.  But there are hundreds of farmers who bag silage as a routine every year, some without every considering building a clamp. So what’s the attraction and why would you choose a bag over a bale?

Well for a start a bag is designed to store chopped forage where a bale is usually formed from longer material. If your feeding plan is based on short chop silage to achieve the intakes you require, - or the forage is going into an AD plant - then bales are just not going to cut it. And whilst it’s not impossible to bale maize silage, it’s not a straightforward process so silage bags or Agbags are the default choice if you need extra maize silage storage in a hurry. So if you’re a chopper based system then bags should be on the radar, but there are also some interesting advantages offered by bags.

One of the big advantages of bag silage is the speed of sealing the forage so the fermentation process can get going. Until all the oxygen is excluded, the aerobic microbes will be busy burning up feed value to produce heat, CO2 and ethanol. The useful bacteria will only hit their stride once all the oxygen is gone. As bagged forage is sealed in the plastic almost from the moment it comes out of the trailer there are some definite advantages here over traditional clamp made silage. This might offer a measurable difference in the dry matter loss during fermentation - it’s not going to be massive but it is significant.

Can you make good silage in a bag?

Getting the silage compacted correctly in the bag isn’t simple, but it is definitely possible with good operators and attention to detail, so you can make good silage in a sausage. Getting compaction that’s comparable with clamp silage is more difficult however. In some trials in North America it was common for the compaction to vary widely across the section of the bag. The shoulders and top of the bag had less than half the density of the middle and base. That’s not ideal but it might not be a complete disaster if you are going to use the silage quickly.

Can bagged silage reduce losses?

There is a bigger potential advantage of bags over clamps and there are situations when sausages are really the wisest choice and it all comes down to feed out losses. Elsewhere in these articles you will find me banging on about feed face advance; how the face of the silage needs to be moving backwards at a minimum of 2m per week. Well that’s all very well in theory, but for some situations its just not practical. Yes the main clamps probably can be designed to meet this requirement, but what if you introduce a new forage into the mix. Say you’re tempted into growing forage peas, red clover or whole crop, how do you store that and use it at the required 2m per week?

This is where the bag might just be the answer. Yes it’s possible to layer “alternative” forage into traditional grass silage clamp, but is a silage sausage a better solution than a silage lasagna? I would think it’s certainly worth considering because the small cross section of a silage sausage makes it easy to work back through it quickly and therefore minimise feed face losses.

Bags are also available in a range of diameters too, so you should be able to choose a size that fits perfectly for this years storage and then choose a different size if your plans alter next harvest.

Getting silage out of the bag?

This is where the problems begin for me because I just can’t see a good solution for getting the silage out of the bag. Yes you can use a traditional shear grab and load silage into the feeder wagon but its all plastic, mud and spillage in my experience. I have yet to see a bag silage ration that doesn’t contain a reasonable plastic content - I sure not everyone has this problem, but I haven’t seen a clean one yet.

Now in North America bags are often used as grain storage and they have some pretty simple but effective machines that empty the bag and wrap up the waste plastic as it works, maybe we need something along the same lines for silage. Such a machine might exist but I’m not aware of one.

Is bagged silage covered by the SSAFO regulations?

So you might be thinking bagged silage could work for you, but where are you going to put one (them)? And once you start thinking about where you’re going to put a silage bag you should also start thinking about the rules and regulations over silage storage - the SSAFO regs. Silage bags have been around long enough to be covered by the regs, and so you really do need to think about this before you start stuffing silage in.

The location for ANY stored silage (clamps, bags or bales) must be a minimum of 10m from any water course, and 50m from any drinking water source. If it’s outside in a field then this 10m figure includes land drains! In addition you must make provision to contain any effluent run off - just like you would from a clamp. This sounds a bit excessive but at the end of the day, if you’re storing 2000t of silage in a bag or a clamp, there is still the same potential to pollute the environment.

The SSAFO regulations are currently a bit easier on bagged silage sites than clamps but I can see that changing at some point. Rats have a habit of chewing though plastic to get to somewhere warm, and if that happens to release a torrent of fresh silage effluent there isn’t much to stop it. Concrete walls take a bit more chewing through so I can see one major pollution incident and they will clamp down on bags overnight.

What is not entirely clear is the requirement for effluent tanks and the minimum sizing set out in the regs. Many believe that they don’t need an effluent tank if the silage is stored on a bag. I read the regulations differently but ultimately how the wording is interpolated will come down to what the judge thinks because be assured - if you pollute, you will be prosecuted - tank or no tank!

Silage sausages and the environment

The effluent pollution potential is just as great irrespective of how the silage is stored, but what about the wider environmental implications for using a bag over a wrapper for instance. Well although bags do use a lot of plastic, they use a lot less than bales when compared tonne for tonne stored.

So silage bags definitely have some challenges but they also have some significant advantages too. I would suggest that a bag solution can provide you with great silage if you’re prepared to pay attention to all the details. What it won’t do it give you a short cut to clamp silage without having to buy all that concrete. It’s a different solution to a very specific set of requirements in my mind. Bagged silage suit farms that need relatively small quantities of silage that would make a clamp unworkably narrow, or it’s a good lifeboat when you’re drowning in a flood of forage.

If you want to discuss more about any aspects of bagged silage or would like to discuss any other aspects covered in this series, contact me at jeremy@silageconsultant.co.uk