Mike Corrales and his employees bale and stack about 20,000 tons of hay a season, and most of the stacks are tarped. But somebody else does that job.

“We've bought tarps in the past and have done it ourselves,” says Corrales, of Basin City, WA. “But it doesn't work for us.”

That's because tarping hits at their busiest times. Besides mowing and raking, his crews bale and stack up to 400 tons/day in haying season. They don't have time to cover stacks, too.

“We've tried putting it off until later, and it never fails — we get hit with a rain,” says Corrales.

Now he has his stacks custom tarped. He makes one phone call at the start of each cutting, and a tarping crew takes it from there.

“They know exactly what I'm doing and the progression of my fields,” he says. “They just show up every day at the next field and tarp.”

In addition, the custom tarpers monitor his stacks for up to a year, periodically tightening the tarps, mending any tears, and making sure they're properly tied back after hay is removed.

“We don't even have to roll up the tarps at the end of the season,” Corrales reports. “They come out, roll them up and take them home.”

He's by no means the only hay grower who relies on custom stack tarpers. He estimates that 90% of the growers in his area go that route. And custom tarping has caught on big time in concentrated hay-growing areas throughout the West, where most hay is stacked outdoors.

Good service is one big reason, says Tim Ravet of Tarp It, Ellensburg, WA, the company that Corrales uses.

“The service has been good enough that they don't have to go to sleep worrying about their hay,” says Ravet. “They trust that somebody will be there to take care of it.”

Growers would rather focus on what they do best, adds Glen Knopp of Inland Tarp & Cover, Moses Lake, WA.

“Everybody's getting more specialized,” says Knopp. “Growers who do a good job of growing and putting up their hay many times don't have time to do a good job of tarping, too. So they have us do it — we're the experts.”

Custom tarping has gained popularity as the need to cover stacks has grown. A few years ago, hay slated to be moved the same summer often wasn't tarped, and overwintered stacks in many cases weren't covered until fall.

“Nine years ago when we started, 25% of the hay put up was covered, and now 80-90% is covered,” says Ravet. “Almost all of it is covered by October. But even during the summer months, 80% is covered as soon as it's taken off the field.”

Long-distance marketing has fueled that change, says Dick Carter of Western Ag Enterprises, a tarp firm headquartered in Phoenix, AZ. Hay today is commonly shipped across the U.S. and even to other countries.

“In some cases, the cost of transportation and handling far exceeds the initial cost of the hay,” says Carter. “You don't want to ship lousy hay halfway around the world.”

Carter's company, operating mostly in Arizona, Kansas, Colorado, Idaho, Washington, Oregon and California, is the biggest tarp firm, custom covering roughly 2.5 million tons of hay annually. That figure includes the volume of Tarp It, which operates independently but handles Western Ag tarps. The company also custom covers bunker silos and silage piles in certain areas.

Inland Tarp, doing business throughout the U.S. and southern Canada, is the second biggest custom tarper. It custom covers about 2,000 stacks per year, plus several other companies do smaller amounts.

These companies also sell tarps, but custom tarping accounts for more than half their business.

Technically, they rent tarps to growers under contracts that typically expire on May 15 the following year, and the rental fee includes tarp installation and maintenance.

The cost varies with stack configuration and other factors. But covering just the top of an alfalfa stack typically runs $2-5/ton. Covering the sides and ends, too — which eliminates bleaching — adds $2-3/ton.

The fee is calculated by linear foot — so high, wide stacks are the least costly to tarp. Hay targeted for export often is more expensive to tarp than hay that will be sold domestically. That's because higher-quality tarps are used. And lighter hay such as timothy costs more to tarp on a per-ton basis than does alfalfa.

Corrales, who sells most of his hay for export, currently pays $4.50/ton to have about 17,000 tons tarped. That comes to more than $75,000 annually just for tarping. But he's not complaining about the cost.

“It's the only way we can market hay,” he says.