Dairy Tries Miscanthus as Bedding Supplement

11/2/2013 7:00 AM
By Philip Gruber Staff Writer

WASHINGTON BORO, Pa. — People who pass Steve Harnish’s field often ask him about the 12-foot-tall plants that cover two acres of land at his family’s Central Manor Dairy.

Harnish has gotten enough questions that he almost put up a sign identifying the tall, woody plant. It is miscanthus, a grass native to Africa and Asia that is gaining a reputation as a biofuel source.

“It’s a little bit like bamboo” but less woody, Harnish said.

Harnish isn’t looking to burn the monstrous, ornamental-looking plant. With help from a Sustainable Agriculture Research and Education grant, he is trying miscanthus as a bedding supplement for the family’s Holsteins.

The Harnishes built a compost bedded pack barn in 2009, which improves cow comfort but requires a large amount of bedding. The bedding ranges from 1 to 3 feet thick and is aerated three times a day.

Central Manor milks 190 cows and houses 50 on the compost bedded pack.

Sawdust is the most popular component of bedding, but supplies get short — and prices get higher — in the winter when more sawdust is made into pellets for stoves and woodshops burn it for heat.

Not just any plant matter can replace sawdust. The bedding needs to be dry, absorbent and able to dry out once it has gotten wet. Many plant products, like corn stubble, just turn to mush when wet.

Around the time the dairy added the barn, Harnish read about miscanthus in a magazine. The article touted the plant for having some of the highest tonnage per acre of any plant used in biomass.

“We’re constantly looking out for something that’s a good value to bed with,” he said.

Miscanthus is used as a bedding material in Europe, especially for horses, although it is not considered as good for horse bedding as straw, he said. He does not know of other U.S. dairies using miscanthus for bedding.

From 2009 to 2010 he shopped for a supplier. When he found a company, he had to wait a year until they had seedstock available. He planted in the spring of 2011.

The type of miscanthus used in agriculture is a sterile hybrid, meaning it lacks seeds and must be propagated either by plugs, which Harnish used, or rhizomes.

Miscanthus has become more widely available since Harnish planted his field, but it remains expensive to start. The plugs are pricey and require a lot of labor to plant.

After spraying at the beginning of the first two springs, though, the plants are essentially maintenance-free because they grow in dense groups.

“Weeds don’t stand a chance,” Harnish said.

The miscanthus started out as five- or six-stem clumps spaced 30 inches apart. They grew from 6 inches to 3 or 4 feet tall the first year, though the field looked almost bare.

Last year, the plants hit almost their full height of 12 feet. Now the plants have filled in further, and little bare dirt is visible.

Harnish skipped harvesting in 2012 because the yields would have been insignificant, but he got 5 tons of dry matter per acre when he harvested in February 2013.

Harnish waited until after the leaves fell off in the winter and the moisture content dropped to 15 percent, and then ran a forage harvester through the field on a day the ground was frozen. He used a row-independent corn head.

“It worked well,” he said.

Harnish expects dramatically higher yields this coming year. Experts say 15 to 20 acres per ton is reasonable, but Harnish will wait until after the harvest before making any claims.

The trial plot takes two acres of the farm’s 220. Because of a wellhead and right of way for the elementary school across the street, manure cannot be spread in the miscanthus plot. Growing miscanthus, which needs no manure, was a sensible way to keep that land in production, Harnish said.

Miscanthus dries down to 15 percent moisture only in the middle of winter, so it becomes available when supplies of other bedding materials are lean. It is also local, so it cuts cost of being trucked in from elsewhere.

After harvesting the second-year growth in 2013, Harnish conducted a trial on the compost bedded pack. He covered one half with sawdust, the other with miscanthus, and he recorded the moisture and temperature.

Miscanthus held up well: The two bedding materials had the same moisture results, and miscanthus kept the pack 4 degrees warmer.

The sawdust pack generally heats to 120 to 140 degrees and functions best over 130 degrees.

Granted, “we had a base of sawdust there” on the miscanthus side of the bed pack, Harnish said. The miscanthus accounted for only about 20 percent of the bedding on its side, and it would take a huge amount of miscanthus to wholly replace sawdust on the pack.

It’s too soon to tell if the project will be cost-effective, but the miscanthus can probably stay as long as Harnish wants it to. Some European fields of the perennial plant have been going for 20 to 30 years, he said.

The cows on the compost bedded pack were unaffected by the miscanthus, but Harnish said miscanthus is probably unsuitable for free-stall barns.

The compost bedded pack is fairly forgiving, but the woody outsides of the plant are too prickly to be comfortable in a free-stall setting where there is less material between the cow and the concrete.

Miscanthus has proved sturdy so far. It stayed upright even when coated with ice and despite a windstorm that felled trees and a neighbor’s silo. It sometimes leans outward on the edges of the fields, but it is just trying to expand as much as possible, Harnish said.

Penn State Extension engineer Dan McFarland helped the Harnishes when they built their bed pack barn. Because the miscanthus project is related to the bed pack’s effectiveness, he signed on to Steve Harnish’s SARE grant application as the required technical adviser.

“It’s a unique opportunity to do it,” McFarland said of the experiment. “There’s some potential for volume, especially at a time of year when the bedding resources may be a little more limited.”

A weaker construction industry and fewer sawmills have also helped reduce the availability of sawdust, he said.

Harnish is the first farmer McFarland has heard of who is trying miscanthus as bedding.

Researchers are investigating the possibility that miscanthus could replace corn as a source of liquid ethanol, said Marvin Hall, Penn State professor of forage management.

Ethanol still represents a small part of the miscanthus biofuel usage. “Most of it is just burned at this point,” Hall said.

Hall has been growing and researching miscanthus for about six years, but few other people have been growing it in Pennsylvania. One company in the state’s northwest is contracting with farmers and hopes to grow perhaps 50,000 acres some day, though it is nowhere near that point yet, he said.

As for miscanthus’ use as bedding, “I assume it’s a possible; I’ve not tried it as that,” Hall said. “As dry as it is, you’d think it’d soak up a lot of liquids.”

If miscanthus works as bedding, that is an added bonus to a grower in case the biofuel market falls, he said.

Hall has not heard of anyone trying to use miscanthus as forage. The woody plant’s questionable palatability and high startup cost are likely reasons.

Miscanthus is attractive because it can grow on less-than-ideal soils and uses little water. Still, compared with wheat, oats and straw, Hall said miscanthus makes a lot of dust when chopped, and the dust can be itchy.

Hall also is concerned that some companies may sell an invasive cousin of the preferred agricultural miscanthus hybrid. That is particularly problematic because miscanthus, unlike switchgrass, another versatile biofuel plant, is not native to Pennsylvania.

Harnish said his plants are seedless, so invasiveness is not an issue. Tillage and herbicides kill the plant’s rhizomes.

Anyone interested in watching Harnish’s miscanthus harvest this winter can email miscanthus@cmdairy.com to be notified when Harnish sets the date.


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