Three factors are important in choosing a bale wrap -- be it sisal, plastic twine, net-wrap or tube-wrap -- says Kevin Shinners, University of Wisconsin ag engineer.
1) Productivity in the field. Twine is a lot slower in the field to wrap bales with than net-wrap, Shinners says. Baling productivity with net-wrap can be increased 30-35%, depending on bale size and number of wraps. Most balers can add net-wrap features for $3,000-4,000, and it costs about $1/bale more than twine, depending on how much is used. Generally, 1 1/2-2 1/2 wraps with net-wrap is sufficient.
2) Losses that occur during storage. In Shinners' research, average dry matter (DM) loss for sisal twine was 19.5%, 11.3% for plastic twine, and 7.3% for net-wrap.
"Sisal twine generally won't survive the storage period without rotting away on the bottom of the bale," Shinners says about uncovered bales stored outside in humid climates. Such bales will begin to sag, enabling more water to penetrate. Plastic twine holds bales together better, which helps shed water better.
Net-wrap is even more effective, but these bales must be placed on a well-drained surface so water doesn't pool at the bottom of bales.
Tube-wrapping is another option. Baled at 30-35% moisture vs. the traditional 18-20%, tube-wrapping saves a day in the field and works well for producers in humid, rainy climates. DM losses were well below 7% in Shinners' research, and often below 3% (comparable to barn storage).
The roles are reversed if bales are stored inside or covered with a tarp.
"Sisal twine really has an advantage because you can drop the whole bale into the feeder and the twine will disappear," Shinners says. "A net-wrapped bale has no advantage stored indoors," except in productivity in the field.
3) How you plan to feed bales and the time you have to feed. "Even if you're inclined to get off the tractor at feeding and cut the wrap, it can be problematic to remove," Shinners says, especially net-wrap with snow and ice accumulation. Once removed, plastic twine and net-wrap often ends up wrapped around equipment such as mower shafts and manure spreader beaters.
That's one of sisal twine's big advantages -- producers don't have to worry about removing twine strings before feeding bales.
If you're going to sell hay, net-wrapped bales have better visual appeal than twinewrapped hay. And net-wrap that covers over the bale's edge is better than regular.