Research into the benefits of single sheet high oxygen barrier (HOB) films compared to multiple sheets of traditional black plastic have shown significant productivity and environmental benefits, says Tim Brewer of silage film specialists Silostop.
Trials from around Europe and further afield have shown significant reductions in silage waste, improvements in feed quality and an overall reduction in energy use and associated carbon footprints, he explains.
“One of the most compelling of these is a meta-analysis of over 50 individual pieces of work which showed a reduction in waste of 42% in the top layers of clamps sealed with a high oxygen barrier film compared to standard polyethylene film.
“The proportion of silage judged to inedible by livestock was also reduced with material stored under the HOB film compared with the standard film covering system and the aerobic stability of the uppermost layer of silage under the HOB film was much greater too.
“These results correlate with work carried out at the INRA Research Centre in France where HOB film gave a total silage loss of just 7% compared to over 15% with traditional black polyethylene film.
“The trial was carried out using a Silostop covering system as the HOB film with protective net and gravel bags to secure it compared to a standard polyethylene film weighed down by tyres.
“A single crop of primary growth perennial ryegrass was harvested on 12th and 13th June after a 48-hour period of field wilting and was ensiled in adjacent silos simultaneously without any additive. Period of storage for both was 240 days.”
Despite the same approach for both silos, very different results were seen when they were opened, he explains.
“Whilst mean silage density was similar for both, the total amount of silage DM removed for feeding was 17% higher with the HOB material, reflecting lower losses during the storage period.
“Butyric acid concentration was much higher in the polyethylene covered clamp compared to the Silostop HOB one – 17.2g/kg DM as opposed to 7.35g/kg DM – indicating poorer fermentation quality in the traditionally covered clamp with a correspondingly lower pH for this clamp too.
“The study clearly demonstrated the extent to which total losses can be reduced and silage quality improved using an oxygen barrier film compared to the standard silage covering technique.
Advantages of HOB film extend to environmental ones too, he says.
“Covering ensiled forage maize with a single layer thin HOB film has been shown to give large reductions in primary energy and greenhouse gas production compared to the normal practice of covering clamps with two layers of standard film which is much thicker.
“Work in the Netherlands has shown the total weight of plastic used in a 40m long by 12m wide clamp using standard film to be 241.5kg whereas with an HOB film it was only 43.4kg – just 18% of the standard film weight.
“In terms of primary energy needed to produce the film at 78.1 MJ kg film this was 18.9 GJ for the standard film and 3.39 GJ for the HOB one. So it’s taking less than 20% of the energy to produce the HOB film for a silo compared to that for the standard polyethylene approach.
“When it comes to greenhouse gas reduction, whilst the manufacturing of the HOB film released 92.3 kg CO2 to the atmosphere, with the standard film it was 514.4kg – over 5.5 times more.
“At a time when everybody needs to produce their home-grown forages as efficiently as possible whilst limiting any harmful effects on the environment, HOB films have an awful lot going for them.
“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.
“We wouldn’t tolerate 15% storage loss for any other agricultural product yet as the research shows that is often the case with clamped forages.”
“Our experiences in the UK suggests a drop in silage wastage from 15% to 5% as a result of better clamp sealing when people switch from traditional black plastic to HOB films is a common outcome.”
FIVE KEY MANAGEMENT AREAS TO GET THE BEST OUT OF HIGH OXYGEN BARRIER FILMS
Tim Brewer recommends looking at five key management points when switching over to HOB films.
1. Plan ahead
Single sheet films are available in range of sizes and the best fit will depend on individual circumstances, he explains.
“For a start, you’ll also need to be sure you can handle the weight and size of rolls selected and work out whether going from side to side across the clamp is the best option or if going from front to back is better.
“The overall aim is to keep the number of joins to a minimum to avoid potential air ingress, so it’s best to work with somebody who understands the different fims and sizes available and who can help you make the right decisions.
2. Make sure you’re using a genuine high oxygen barrier
Not all plastic films are created equal and it’s important to choose a genuine high oxygen barrier if you want to get the best results, he adds.
“A proper high 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.
"These thin transparent polyethylene films can appear to give a reasonable result with a visual reduction in top layer spoilage, but their extremely high oxygen transmission rates results in high DM losses.
“We’ve also ensured all our films are recyclable, but that’s not the case with all films.
“Again, you need to talk to somebody who understands this and be prepared to ask the questions about oxygen transmission rates and recycling.”
3. Use sidewall sheeting wherever possible
Once you’ve made your overall plan, sealing the sides of the clamp using an appropriate wall film is the first operation you should carry out, he says.
“Make sure the clamp is as clean as possible then line the walls with side sheeting to make sure oxygen cannot enter through the walls.
“Ideally, leave 0.5m of film at the base of the walls so it overlaps onto the floor of the clamp. This will help secure the film when the silage starts to be put in.
“An extra 1m of film should also be left at the top of the wall so this can be folded back over the silage once the clamp is full. Make the silage surface as dense and smooth as possible by lots of rolling.”
4. Manage films correctly
Type of forage will also play a key role in choosing the optimum film, Tim Brewer points out.
“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.
“Silostop Anti-UV covers, for example, provide full UV and physical protection and are designed to work in conjunction with just one layer of thin but strong Silostop Orange HOB film.”
5. Secure films properly
Whichever approach you take, bags and purpose-made mats are the best materials for keeping covers in place and minimising pest damage, he advises.
“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.”