Saturday, June 27, 2009

A very, very brief guide to composting

The process of making compost scares off a lot of people, but if you follow a few rules, it's actually fairly easy. There are a number of guides out there to help you learn the basics, but we'll cover the most important points in this blog. (Pick up one of the books recommended below for more information.) Compost is perhaps the most important element of any garden plan. As the British garden writer Monty Don says: "No garden should be without a compost pile. No organic garden can be without one."

First, what is composting?: It's basically controlled rot, even accelerated rot. Most people associate "rot" with things that are poisonous and smelly. That's anaerobic (or oxygen-deprived) rot. Composting is aerobic (or oxygen-rich) rot. Basically, you are trying to create a rotting environment that has lots of access to fresh air (through turning the pile), which will not only make the decomposition happen faster and preserve plant nutrients, it also will not smell. Well-made, finished compost -- which is rich in organic materials -- smells like good, clean dirt.

Where to compost?: Compost can be produced in an open box or open pit, but since we're here in the 'burbs, where people get fussy about the appearance of a yard, we recommend buying a commercial compost bin. Baltimore County sells the Earth Machine composter every spring for around $35 -- a bargain. There are lots of other bins available out there. We recommend one like the Earth Machine that puts the compost in contact with the ground below (rather than keep it off the ground, like the ComposTumbler brand), which will allow underground creatures to invade the compost and help with the decomposition. Also, Earth Machine-type composters can be set directly on beds where you plan to grow, making the ground under them very fertile. Just move the composter around year-by-year. Your composter should be an enclosed container with a cover. Use that cover. Also, buy a compost turner -- a wand with a handle that has two wings on its point that open up when you pull it up through the compost. This tool helps mix and aerate the pile. (Watson's Garden Center, on York Road north of the Beltway, sells sturdy turners for around $25.)

What can be composted?: It's better to answer this question by listing what cannot be composted (at least in home-scale systems): Do not compost bones, meat, oils and fats, dairy, or any kind of synthetic or non-organic material, like plastic bags, chemicals, or aluminum cans. The bones, meat, et al., will smell and attract pests; the synthetics won't break down. You're better off sticking with yard waste. Vegetable trimmings, egg shells, coffee grounds, and other organic wastes from the kitchen are frequently used as compost material, but composting food is against the rules in Baltimore County. (It is allowed in the city, so ponder that little mystery.) If you want to play by the rules, you might want to start a worm-compost bin. You should also avoid composting pernicious and invasive weeds, or their seeds. There's a chance that they will not die or that their seeds will not be sterilized in the heat of the compost pile, and then you'll have a big problem when you add that compost to your garden.

How do you get started?: Compostable material is either a nitrogen-rich "green" or a carbon-rich "brown," and you need a certain mix of the two to get good compost. Grass clippings are a "green." Fallen leaves or shredded paper are "browns." But don't go by color: Manure and coffee grounds are compost "greens," even though they are brown in color. Got it? Here's an easy recipe to get started: Mix even portions of fresh grass clippings and fallen leaves in your composter, then use your compost turner to mix the stuff up. (Don't waste your money on compost activators, by the way.)

What will happen next?: Let it sit for 12 to 18 hours and turn it again. You will find that it has started to get really hot. That's good. Themophilic (or heat-loving) bacteria are the first to go to work in a compost pile. They will quickly heat up the center of the pile to 120 to 150 degrees. They thrive on oxygen, so keep turning that pile every day. If anything smells off (like vinegar or alcohol), turn the pile more often and add more brown leaves. If the pile doesn't heat up, add more green grass. You will find that this mixture breaks down really quickly, to about half of its volume. Just keep adding more stuff; the pile needs mass to maintain its heat and action.

When is it done?: When it stops heating up. Just let it sit, or transfer it to a garden bed, where the worms will go to work on it. But I find that if you keep adding nitrogen-rich stuff, along with some carbon, it's never really done. And remember, it doesn't have to be completely done when you put it on a bed.

For more on the compost process, you might look into these books: The Rodale Book of Composting is a classic that we have recommended in the past. Let It Rot! has been in print for decades, and you can still pick up new or used copies everywhere. Composting: An Easy Household Guide is, true to its title, extremely easy and quick reading, but it gives you most of the basic points and more.

If this confuses you, or if you have questions, write us.

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