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Leaves on the wing? Let em fall

Sustainable Life: Composting turns foliage from yard nuisance to nutrient
by: DAVID PLECHL, While Zion Fadel has fun with leaves, many people are putting fallen foliage to work as an ingredient in compost and mulch.

Once they lose their perch as autumnal ornaments, colorful leaves are often seen as an annual chore.

Rake. Scoop. Bag. Tote.

Rake. Scoop. Bag. Tote.

Increasingly, however, people are viewing the season's colorful foliage not as a November nuisance but as a renewable resource.

Leaves are a key ingredient for compost, used to enrich soil in gardens and flower beds. And they're a near-perfect source of mulch, used to curb weed growth and reduce the need for watering.

'Leaves are extremely good to compost,' says Ron Spendal, a certified master composter with Oregon State University and Washington State University.

Here's why. While sources of nitrogen, like coffee grounds, organic kitchen waste and - in our climate - even grass clippings are readily available to gardeners year-round, they're only half the equation of good compost.

'If you're looking for ideal composting, you want an equal volume of carbon and nitrogen,' Spendal says.

Without the right amount of carbon, Spendal explains, you won't get enough microbes, the beneficial bacteria and fungi that break down the organic material.

'If you don't have the right balance, you won't have the heat generated by microbes, so it will take longer and it will be lower quality compost.'

The problem is that many of the things that provide carbon, such as straw, cornstalks and hay, are not readily available to most homeowners. Leaves, however, are just as good.

Compost has many virtues

Turning leaves into a natural soil amendment helps the environment in a variety of ways.

'It is estimated that up to one-third of household waste is organic waste from our yards and kitchens,' says Chris Carey, district manager for Waste Management Oregon. 'This is just the type of material that can be used in compost, rather than crowding our landfills.'

What's more, despite what many people believe, putting biodegradable material into your garbage isn't a harmless act.

'The myth is that food waste and yard waste are not a problem because they break down in a landfill,' says Karen DeBaker, a public information specialist with Clean Water Services, the Washington County agency responsible for treating storm water and sewage.

'The truth is when food and yard materials biodegrade in a landfill, where there is little oxygen, they generate methane gas - a greenhouse gas over 20 times more potent than carbon dioxide,' DeBaker says.

Keeping leaves out of the streets also reduces the chance that storm drains will get plugged and cause flooding.

Moisture level is key

While composing isn't hard (or, if done right, smelly) there's a bit more to it than dumping leaves on top of your coffee grounds.

To start, you'll need a place to store the materials. You can buy composting bins, make your own or just create a pile in a corner of your yard. The general rule is that it needs to take up a space equivalent to a three-foot cube.

Whatever method you choose, creating high-quality compost requires the correct moisture and aeration levels.

That's why Spendal recommends shredding leaves before adding them to the mixture.

'The easiest way is to scatter the leaves and run them over with your lawnmower,' he says, explaining that matter disintegrates more easily when it's in little pieces.

If the leaves aren't shredded, he says, they 'pack themselves into a barrier that prevents air flow, which is needed for the decomposition of materials.'

To ensure optimum air circulation, turn the compost over weekly with a pitchfork. Water concentration can be regulated by either adding dry material or showering the compost with a hose. Evaluating the condition of your compost doesn't require any equipment other than your finger, Spendal says.

'The moisture content of good compost should feel like a rung-out sponge, which has about a 45 percent moisture level,' he said.

When compost is blended well, the activity of the microbes that live in it gradually raises the temperature of the organic mass.

If the compost rises above 135 degrees Fahrenheit for three consecutive days, two things are accomplished: Disease-causing pathogens are killed and unwanted seeds from weeds and plant material are neutralized.

Aside from eliminating unwanted life forms, the microbes restore the soil's biology, which can be disrupted by some gardening practices, Spendal says. 'You're composting to reintroduce microbial life to the soil, so it becomes richly organic as well.'

Waiting for a breakdown

Determining whether your compost is ready to be spread out in the garden is also simple: It will no longer produce heat, it will shrink to roughly half its original volume and its components will no longer be discernible.

'They will all have broken down into dark humus,' Spendal says.

Though it's wise to carefully tend your compost, it's not a good idea to go overboard - fertilizers and other substances designed to jump-start microbial activity are likely to have a detrimental effect in the long run.

Spendal likens using such inputs to 'putting the microbes on drugs,' because once the artificial nourishment runs out, their growth quickly declines.

'It's better to let the microbe population increase at its own natural level rather than chemically induce rapid development that can't be sustained,' he says.

Besides, such supplements are unnecessary if all the other factors have been carefully controlled. Spendal says that under the right conditions, compost can be finished in 10 weeks, even in the dead of winter.

'Even if you have snow on the ground, you can have a 150-degree compost pile, no problem,' he says.

If you find yourself with more leaves than you can use, Spendal suggests storing them for use throughout the year. To prevent rotting, he says, they can simply be heaped in a pile and covered with a tarp.

Find out more

For more ideas about composting and mulching with leaves, the Oregon State University Extension Service offers several publications. 'Gardening with Composts, Mulches, and Row Covers' and 'Backyard Composting' are available through the OSU Extension Service online catalog.

Go to extension.oregonstate.edu/catalog and type 'compost' in the search box. To order a printed copy, call 1-800-561-6719.

Other Web sites include www.howtocompost.org and www.plowhearth.com/magazine/compost_how_to.asp