What's better for wrapping large round bales - twine or net wrap? It's a question Kevin Shinners, professor of agricultural engineering at the University of Wisconsin-Madison put to the test.
Shinners, along with four colleagues, conducted a study in which four bale-wrapping treatments were compared: sisal twine (an all-natural, biodegradable product), plastic twine, to-edge net wrap, and cover-edge net wrap.
The two-year study concluded that net wrap outperforms twine for three reasons.
1. Net wrapping is faster than twine wrapping, which leads to greater productivity. It takes one and a half to three turns to wrap a bale with net; twine requires 20 to 30 turns. In one hour, 32% more bales were formed with net wrap compared to twine.
2. Harvest losses (hay dropping out of the bottom of the baler) are lower when using net wrap because of the shorter time needed for wrapping. The study revealed losses were reduced by 65% compared to wrapping with twine.
3. Net-wrapped bales have lower storage losses (7%) during outdoor storage compared to twine-wrapped bales (11%). Shinners says this is because net-wrapped bales shed water better if they are stored on well-drained areas.
"You have a big advantage with net wrap because you're immediately covering the face of the bale. Twine has to be spooled and takes much more time to wind it around. There is a productivity advantage with net wrap. It's a few seconds vs. a few minutes," Shinners says.
Although net wrap (a fine plastic mesh applied around the bale) has been around since the mid- to late 1980s, the process has seen slow adoption by farmers.
One reason may be the cost. The wrapping mechanism can increase the initial cost of the baler by 15% to 25%, depending on bale size. The net wrap equipment costs about $3,000 to $4,000, and plastic net is $1 to $1.25 per bale more expensive than twine, depending on bale size and number of wraps.
Many producers cannot justify the cost of net wrapping unless the cost of the equipment needed is offset by lower wrapping losses, greater productivity, improved timeliness, and lower storage losses.
There are a variety of net wraps, but their differences are minor. The biggest difference is a cover edge vs. a to-edge net wrap. Cover edge means the cover is going all the way over the edge of the bale by at least 1 to 2 inches. To-edge net wraps go around the entire circumference of the bale but don't extend over the edge.
"To-edge net wrap is the most common type. It's a little less expensive, and not every baler can do cover-edge baling,â€ Shinners says.
Twine is available in sisal and plastic (polypropylene). Sisal is biodegradable, made from natural fiber, and has been the leading material for ag twine. Its importance is diminishing with competition from polypropylene twine and other baling techniques that are being developed.
Even though net wrap has a variety of advantages, it does have its downsides.
"The cost of net wrap is $1 to $1.25 per bale (depending on size) more expensive than twine. It's also more difficult to get rid of since it's not biodegradable. Net wrap has more plastic to deal with, and growers need to dispose of it properly," he says.