Kevin Shinners doesn't understand why so many hay growers in humid climates still wrap round bales with twine.

“Many people don't use net-wrap because they believe it costs more money,” says Shinners, a University of Wisconsin ag engineer. “They're only looking at the up-front cost and not the total value it can bring to their operations.”

In two years of round bale research, he wrapped bales of alfalfa and alfalfa-grass hay with plastic netting and either sisal or plastic twine. Bales were stored for five months or a year, both indoors and out. Outdoor-stored bales were placed directly on the ground or on a well-drained surface.

Shinners found that net-wrap beats twine in three ways:

  • Faster wrapping, which leads to greater productivity.

    Even with dual twine arms on the baler, the time needed to wrap a finished bale with twine can almost equal the time needed to form the bale. In his tests, 20-30 bale turns were needed for twine wrapping, compared with 1¼-3 turns for net-wrap. The result was 32% more bales formed per hour.

    “Productivity enhancement is a tremendous benefit to net-wrap,” Shinners states. “You can easily spend one-third of every hour wrapping bales with twine. That wastes your time, burns extra fuel and adds to tractor wear and tear.”

  • Lower harvest losses. Hay drops out the bottom of the baler during wrapping. The amount is negligible during the short time needed for net wrapping, but can reach 1% or more of bale weight with twine.

    “That could be a significant amount of money, especially if it's a high-value alfalfa crop.”

  • Lower storage losses.

In Shinners' study, dry matter losses during outdoor storage averaged just over 7% for net-wrapped bales vs. about 11% and 19%, respectively, for bales wrapped with plastic and sisal twine. Forage quality also was higher in the outer layers of net-wrapped bales.

That's because net-wrapped bales shed water better. When the bales were removed from storage, twine-wrapped bales were always higher in moisture in the outer 4".

However, when the bales were stored directly on the ground, the net-wrap ones were higher in moisture at the base. Shinners says more water soaked into twine-wrapped bales and most of it eventually evaporated. But it ran off the net-wrap bales and accumulated at the bottoms.

“If you're going to use net-wrap to take advantage of its superior water-shedding ability, you have to put the bales on a well-drained surface,” Shinners advises.

They should be placed off the soil on pallets, old tires, crushed rock or fly ash.

Any round baler can be equipped with net-wrap. The equipment costs $3,000-4,000, and plastic net is 75¢-$1/bale more expensive than twine.

“But based on the numbers we found, just in storage losses alone it can easily return $1.80-2 per bale,” says Shinners. “If you make enough bales, the system will pay for itself rather quickly.”

If you must wrap with twine and the bales will be stored outdoors, use the plastic type, Shinners suggests. Sisal twine rots, the bale loses its shape and water penetrates.

“From the standpoint of bale integrity and loss, sisal twine is a disaster,” he says. “I can't think of a single reason to use it other than it's biodegradable.”