Archive for Thursday, November 18, 2004

Mulching leaves into lawns better than raking them

November 18, 2004

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— Mike Goatley is the kind of guy couch potatoes appreciate most on football-rich fall afternoons. The Virginia Tech extension turf specialist preaches the gospel of "leave them alone" lawn leaf management.

There's nothing wrong with blowing, vacuuming or raking downed leaves -- especially if you're trying to spot errant golf balls or keep your grass from being matted down over winter. Disposal is the problem.

"One of the biggest things we're trying to get away from is putting these things in bags and dumping them in a landfill," Goatley says. "At the same time, you're improving the organic matter in your soil." The technique has been used for years, he says. But "there's quite a bit of data out there now (from Purdue, Michigan State and Cornell universities) indicating this is the way to manage those leaves." In other words, crank up your mulching-capable lawn mower first when the leaves start piling up in autumn.

A Purdue University report details the responses of a perennial ryegrass lawn to the addition of as much as two tons of maple leaves per acre per application. Mowing the leaves into fine pieces and filtering them through the turf doesn't degrade lawn color or quality, introduce diseases or weeds, the report says. Over time, the shredded leaves decompose, enriching the topmost soil layers. Mower mulching also saves time and money that would be unnecessarily spent on bagging and dumping. Composting leaves directly into the turf doesn't mean you should stop fertilizing, however.

"I don't think leaf recycling is a substitute for a sound fertilizing program," Goatley says. "Mother Nature has already removed a lot of nitrogen from those leaves. The microbes needed to further break them down also need some nitrogen.

"Fall fertilization of cold-season grass definitely is the way to go. You can still reap some lawn care benefits with a November nitrogen application."

Applying shredded leaves to your lawn does not alter its underlying soil chemistry, researchers say.

"The deciduous leaves coming off trees have been shown to have a minimal effect on soil pH," Goatley says. "What could make a difference, though, is pine straw (layers of pine needles). That's acidic. The needles also don't break down very quickly."

Grass height depends upon the species, but two to three inches is good for this time of year.

"An advantage to maintaining your mowing schedule into the down time of winter is that the leaves continue filtering down," Goatley says. "You can't completely pulverize them, but they will settle down into the grass and become organic matter."

While you should always think safety when mowing your lawn, that goes double when leaf-mulching.

Wear safety goggles and an air mask, Goatley says. Don't use your mower for branch-shredding or stump-grinding. Sharpen the mower blade and change the air filter more often when mulching thick layers of leaves.

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