August Home-Garden

National Gardening Association Rubbish!

Working too hard at your composting? Here are six rules you can forget.

by Jack Ruttle

People have been making compost for a thousand years and more, time enough for a considerable mythology to have arisen around the practice. Some of the methods for assuring "perfect" compost sound like pure witchcraft. Even a lot of ordinary composting ideas turn out to be off the mark. Certainly, the idea of perfect compost, which has become the holy grail to some gardeners, discourages many others.

So how do we separate the good ideas from the bad? For starters you can't trust all of what you read in books. Many writers simply pass along things written by previous pundits. The composting process is so simple, and so inevitable, that one can do any number of strange things to a compost heap and, given time, it will rot. Invariably, the most arcane practices and exotic ingredients are credited with the success. The antidote is to keep things as simple as possible and to base your opinions mainly on your own experience.

I've spent 20 years now making compost, reading everything about it I can get my hands on, and attempting to debug the myths. Here are six commonly held notions about compost that you can ignore.

GOOD COMPOST IS TURNED AT LEAST ONCE OR TWICE.

No need to feel like a second-class gardener if you don't have the energy to turn a compost pile. Eventually, everything organic will rot completely as long as it's kept moist enough for molds and bacteria to grow. Without any attention from the gardener, a pile of leaves might take a year or so to rot, while an oak log might take five years or more.

The reason people turn compost is to speed the process up. When the aerobic microbes that make compost run out of air, they slow way down, and turning puts air back into a pile. When conditions in the pile are right, an energetic composter can get ready-to-use compost in two weeks by turning it every third day or so -- whenever the temperature begins to drop. Without turning, the pile would be ready to use in about a year. But the compost would be just as good, if it had been shielded from nutrient-leaching rains. Each turning cuts the rotting time by about half.

TO MAKE HOT COMPOST, YOU NEED MANURE.

Rapidly multiplying aerobic microbes make a compost pile heat up. This population explosion usually occurs when a large amount of fresh material is first made into a pile. One reason is that fresh piles are full of air. Another reason is that fresh materials are often rich in nitrogen. But let's face it, finding manure and using it without affront to the neighbors can be tricky in many neighborhoods. Fortunately, there are plenty of other nitrogen sources.

All green plant materials are good nitrogen sources: kitchen trimmings, weeds and leaves, and perhaps the best known for rapid heating -- grass clippings.

In composting recipes, you'll often see nitrogen-rich compostables called the "greens" and energy-rich compostables called the "browns." Mix greens and browns (straw, old hay, autumn leaves) together in a ratio of one or two parts green to three or four parts brown. Moisten the pile slightly as you go if any of the browns are very dry. You should get surefire heating within a day. A pile that doesn't heat within 24 hours lacks enough nitrogen to fuel the population explosion.

Shredders and tumblers are necessry for quick compost?

When my first efforts at composting did poorly, I began to suspect that a shredder might be the answer. But before I bought, I did some reading. I found plenty of writers who claimed that the reason shredding worked so well was that it greatly increased the surface area on which bacteria and fungi could grow. That seemed to make sense. Then I came upon a slender volume called simply, Composting. The writer was Clarence Golueke, an engineer doing research on composting at Berkeley.

What interested me most in his little book was a detailed description of one of his "backyard composting" experiments. He found that a pile built and turned with nothing more than a shovel and a fork could get just as hot and rot just as thoroughly as piles shredded and tumbled with up-to-date heavy equipment. Even a whole head of cabbage rotted. Cutting things into tiny particles, he concluded, really doesn't matter.

Though a bit skeptical at first, I followed his example and was able to duplicate those results easily. I've done it many times since. Apparently the bacteria and fungi find all the exposed surface area they need on wastes pretty much the way they are. Shredders are great for reducing the space that bulky materials (especially tree branches and vines) take up. But don't let the lack of one get in the way of your composting.

Thick, woody branches are a special case. Wood is almost pure energy, with virtually no nitrogen or air mixed through it. Shredded branches will rot faster than ones left whole. But wood chips are still very slow rotters: air and nitrogen are plentiful only on their surfaces.

IT'S GOOD TO LET RAIN WEATHER YOUR COMPOST

Actually, rain can quickly leach potassium and nitrogen out of a pile. And when a compost pile becomes waterlogged, air is driven out and composting slows. One of the most serious problems I've had in trying to compost newspaper is that the stuff holds too much water, and it becomes oxygen starved and smelly.

I recommend adding just the right amount of water when a pile is made, then covering the top of the pile with a water-resistant tarp or derelict plastic garbage bags. Compost should be moist and springy to the touch, but not dripping. Fresh grass clippings often contain all the moisture I need in a new heap.

ADD SOIL TO THE HEAP TO INTRODUCE MICROORGANISMS

Dr. Golueke, the compost scientist, also looked for the kernel of truth in this old chestnut and found there just wasn't anything there. It turns out that so many bacteria and fungal spores occur naturally on just about everything that adding an "inoculum" is superfluous. Moreover, lab-reared inoculums, he learned, don't compete well with the wild ones. I have since eliminated adding layers of soil in my compost piles and things rot just as fast.

The advantage of leaving out the soil is that you reduce the work of making the compost and the finished product is lighter. Of course, putting in some soil doesn't really hurt anything either. There just isn't a single advantage to it.

COMPOST IS REALLY A SOIL AMENDMENT, NOT A FERTILIZER.

On technical grounds, I will instantly concede this point to anyone who wants to insist on it. Good compost may be too low in soluble N, P and K to qualify as fertilizer, but that doesn't mean it's just filler, on a par with sand or peat moss.

Compost is packed with all the minerals that plants need, in very favorable proportions. After all, compost is basically just highly concentrated plant material. Freshly made compost continues to break down fairly rapidly for a year or so, releasing those nutrients along the way. I have grown many fine vegetable gardens with no other fertilizer than an inch or two of pure compost applied once a year, and I know plenty of other gardeners who do the same.

Five Tips for Easier Composting

Mix at least two materials. A pile made of just leaves or just grass, for example, will tend to mat together and become anaerobic. (If it smells putrid, it's anaerobic.) Alternating layers of unlike materials is the remedy.

Make a pile at least three by three by three feet. Dr. Golueke's research indicates that this is the minimum critical mass for good heating. Piles taller than four or five feet are laborious to turn and tend to compact under their own weight.

Let it mature. At some point you should stop adding to a pile and start another. An unturned pile will be ready about a year after you STOP adding to it. Each turning cuts decompostion time roughly in half, if nutrients and moisture are right.

Cover it. Excess water drives out oxygen and carries off precious potassium and nitrogen very quickly. Covering the pile with something waterproof recycles the water released during decay and keeps material on the outer edges moist enough to keep rotting.

Make a separate pile for branches. Very woody materials get in the way when the time comes to turn or apply the compost. Stack them by themselves out of the way to rot slowly. Or shred them into mulch for shrubs and garden paths.

Copyright NGA

Reprinted with permission HouseNet, Inc.

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