How you seal your silage clamp can have a huge effect on the speed and efficiency of the clamp-filling process, the quality of forage ultimately produced and the labour hours needed to maintain it once it is opened for feed-out.
According to Lucy Johnson of film specialists Silostop, it’s seen as such a critical part of US dairy production that teams of professional ‘clamp sealers’ now move from farm to farm at forage harvest to ensure the process is carried out as effectively as possible.
“It’s a very different situation in the UK,” she says.
“The number of people still using a range of variously-sized black plastic sheets plus a few worn-out tyres with rusty wires thrown on top is still worryingly high, especially when there is such a downside to not sealing a clamp properly.
“Not only will fermentation be adversely affected, clamp losses will be high and much of the money spent on Nitrogen and other inputs will be wasted, not to mention you’ll be forced to rely more on bought-in feeds.
“We wouldn’t tolerate 15% storage loss for any other agricultural product yet that is often the case with forage.”
But such losses can be kept within 5% if some simple steps are followed, forage specialists believe.
1. Plan your sealing priorities carefully
The starting point is to talk to a specialist and work out exactly how are you are going to seal the clamp and what you will need to do this, says Will Wilson of silage clamp experts ARK Agri.
“You’ll need to know the exact dimensions of your clamp to do this. The most effective method is a single sheet system, but these are available in range of sizes and the best fit will depend on individual circumstances.
“In some cases, going from side to side across the clamp is the best option, whilst for others it will be going from front to back. You’ll also need to be sure you can handle the weight and size of rolls involved.
“The intention is to keep the number of joins to a minimum to avoid potential air ingress, so a purpose-made side sheet is essential, too.”
2. Make sure you’re using a genuine oxygen barrier
Silostop’s Lucy Johnson says it is important to understand not all plastic sheets are created equal.
“A proper oxygen barrier will have an oxygen transmission rate of less than 5 cm3/m2 of film, which means almost no air can get into the clamp in use, but with typical black silage plastic this is more like 300 cm3/m2.
“When this is stretched out to make an imitation oxygen barrier cling film, it can reach 1000 cm3/m2 so quite a lot of air is able to pass through the film resulting in considerable spoilage and dry matter shrinkage in the top layers.
“Again, you need to talk to somebody who understands this and be prepared to ask the questions about oxygen transmission rates. A good film will virtually eradicate air from the clamp, a cheaper one could cost you dearly in terms of lost forage.”
3. Minimise your use of plastic
A modern single sheet system will not only minimise forage wastage, it will also help ensure you are using as little plastic as possible on-farm, she says.
“Nobody wants to use more plastic than they need to. On a typical 16m wide by 50m long clamp, conventional black plastic with cling film will weigh around 110 kg, whilst with our most popular single sheet (Silostop Max) this would be only 66kg.
“Furthermore, if you were to use an Anti-UV cover over a thinner film (Silostop Orange) the weight could be reduced to 38kg - which is a reduction in plastic use of 65% compared to the traditional approach.
“We’ve worked hard over recent years to ensure all our films are 100% recyclable and this is another reason to be using plastics as responsibly as possible.”
4. Manage films correctly
Type of forage will also play a key role in choosing the optimum film, adds ARK’s Will Wilson.
“If you’re using a multi-cut system, where you will be repeatedly opening the clamp up to add material, a stronger film is advisable. This can then be used with a secure cover.
“If you’re clamping maize or wholecrop silage where the clamp is filled and then left until it is opened, the lighter sheets with an Anti-UV cover are the best option.
Whichever approach you take, bags and purpose-made mats are the best materials for keeping covers in place and minimising pest damage, he adds.
“The other advantage is that sheeting time can be cut in half and that’s important in making sure clamps are sealed every evening when you are filling them and also whenever you remove material from it over the winter.
“The easier this is to do, the more likely it is to happen and this alone can help minimise silage loss considerably.”
5. Constantly review performance
Keep an open mind about the future including the silage clamp itself and how it can develop to improve the efficiency of your silage making in the future, Will Wilson adds.
“We’re learning more about the best way to make silage all the time and when the cost of inputs and bought-in feeds is rising so quickly, it’s essential to make full use of every kg of forage you produce.
“Ensiling losses can be avoided in the short-term with the right sealing system, but longer-term you need to make sure your clamp remains fit for purpose, has the right capacity for your future needs and will keep the Environment Agency happy.
“With home-grown forage increasingly critical to the economics of dairy production, such investments are seldom wasted and in many cases significant returns on investment can be achieved very quickly.”