By rights, extra stretching of bale wrap film to make it go further should reduce its ability to keep oxygen out of the forage it protects. But while that may be true for conventional films, it is not the case with a new generation of materials designed to provide an effective barrier despite being stretched significantly thinner.

First on the scene is Swedish manufacturer Trioplast with a film that UK distributor Volac calls Topwrap 2000.

The title highlights the fact that each roll contains 2000m of stretch film rather than the usual 1500m. Yet the rolls have the same dimensions as for other films, so the new wrap will readily fit existing wrappers without modification.

There is only one answer to this apparent trick: At 19 microns, the new film is 24% thinner than usual.

“Plastics technology has moved on enormously over the past 10 years and we’ve taken advantage of that with this new material,” says Jim Davidson of Trioplast. “There are new polymers, a different recipe for the plastic and an additional step in the production process that pre-stretches the film before it goes on to the roll.”

The film is stretched again on the wrapper to the same extent as existing materials; the only obvious difference is that because the film is pre-stretched at the factory, it exhibits less “neck-down” than usual. This is the term used to describe the way stretch film narrows when it is tensioned between the bale and the pre-stretch unit on the wrapper.

The difference in neck-down characteristics between the conventional and factory pre-stretched film is compensated by making Topwrap 2000 only 730mm wide instead of the standard 750mm. As a result, it still goes on to the bale at 650mm wide.

Being able to use the new film without having to modify wrapping machinery in any way was an important objective of the product development process, says David Neville, Volac sales and marketing director.

“We couldn’t introduce a new material and try changing current techniques or expect users to alter their machinery,” he says. “It had to meet or exceed industry standards in terms of both usability and performance.”

Having field tested more than 1m bales and arranged independent evaluations, Mr Neville is confident that objective has been met.

In quality trials, silage from bales made and wrapped with Topwrap 2000 at SAC Crichton Royal, Dumfries and Writtle College, Essex, exhibited equal if not slightly better fermentation characteristics than bales from the same field wrapped in standard Topwrap film.

“The nutritional value of the bales wrapped using the new material was not compromised,” reports Jenny Bell of SAC. “In fact, the silage in these bales analysed exactly the same for pH, ME and protein as those wrapped with standard film in our trial.”

As with conventional Topwrap, Volac recommends using a six-layer application for all round bales made of material with 35% or more dry matter content, as well as for all square bales and heavy round bales made of chopped grass.

For users, the main benefits come from having a greater length of material in each roll. Since each Topwrap 2000 roll carries 33% more plastic (while weighing the same as a 1500m roll), it can wrap up to 10 more bales than traditional film.

That can make quite a difference to a day’s baling and wrapping, says Dumfriesshire contractor Alistair Kingan, whose AK Farm Services operation at Lochhill, New Abbey, typically produces 15,000 wrapped round bales a year.

“We row up, bale and wrap up to 600 bales a day using a McHale Fusion and previously would have to stop more than 10 times to reload with new rolls of conventional wrap,” he points out. “With the longer rolls, this has been cut to eight and thanks to the time saved we’ve been able to step up hourly throughput from 50 to between 55 and 60 bales.”

Moreover, he reckons the film is as strong as conventional materials and goes on to the bale just as well. With fewer cores and boxes involved, there is less packaging to take away at the end of each job.

In a similar vein, the cost to end users of disposing of used plastic via a recycling scheme will be reduced for a given number of bales because of the reduction in weight of material used to wrap them.

Topwrap vital statistics

Topwrap standard

• Width 750mm
• Width on bale 650mm
• Thickness 25 microns
• Roll length 1500m
• Bales per roll (six layers) 30-34
• Colour black or light green

Topwrap 2000

• Width 730mm
• Width on bale 650mm
• Thickness 19 microns
• Roll length 2000m
• Bales per roll (six layers) 40-44
• Colour black

SilotitePRO

Another second-generation silage film – SilotitePRO – is due for launch in time for next year’s silage-making season after a £10m refit of the agricultural film production plant at Leominster in Herefordshire operated by British Polythene Industries (BPI).

“Opportunities to make such wholesale investments don’t come along very often, so we dedicated considerable time, effort and energy into getting it right,” says BPI Agri commercial director, John Lancaster. “We spent two years identifying a state-of-the-art production plant and a further 14 months were required to build, install and customise the new machinery to the exacting standards we required to produce high-performance balewrap.”

The plant, which is now fully operational and working around the clock, has significantly increased production capacity for bale wrap products like BPI Silotite, BPI Polybale and Visqueen Poliwrap. It has also prepared the way for making high-performance films with a thinner profile.

According to preliminary plans, rolls of SilotitePro will be 40% longer than usual, containing 2100m of film rather than the usual 1500m, as a result of being pre-stretched to a thinner gauge as part of the production process.

Users will get more output from wrapping machinery thanks to less frequent stops to change wrap reels and enjoy a reduced waste disposal burden thanks to the reduction in packaging and plastic involved in wrapping a given number of bales.