Compost, a favorite soil amendment and mulch for gardeners the world over, is an excellent source of organic material for any part of your garden.
It is the magic elixir for troubled plants as well as poor soils. It improves the lightness and workability of various soils. It boosts water retention in sandy soils and aids in drainage in clay soils.
But compost, especially making your own, versus buying it bagged, is complicated. Here's an overview of this magical, biologically complex black gold.
What compost is—and isn't
Compost is the decayed remains of organic materials. It's that simple. Microorganisms eat whatever you feed them and turn it into particulate matter that in turn aids plants in absorbing nutrients from the soil for use during their growth cycle. Compost provides nutrients itself as well, depending on what ingredients were used.
Compost is not fertilizer. It can be used in conjunction with both organic and inorganic fertilizers or soil amendments to provide your plants a complete diet, though.
Compost is not potting soil. By itself, compost lacks enough structure to be used as potting soil. It also contains microorganisms that may or may not be good to contain in a potted environment. Sterilized compost can be used with other sterilized materials to make potting soil or seed starting media.
Compost is not dirt. Just because it looks like soil, smells like soil, and tastes like soil doesn‘t mean it is soil. Compost is organic matter and aids plants by loosening the soil.
What to compost
Theoretically, you can compost any plant material or byproduct, and any manure produced by vegetarian animals. However, there are some exceptions and preferences.
The vast majority of other common plant material and farm-type animal manure can be used. Most common plant materials are fallen leaves, grass clippings, hay, straw, garden plants, deadheaded flowers. Common animal manures are horse, chicken, cattle, and rabbit. Horse manure must be thoroughly composted before using it. If it is not composted first, weed seeds in it may germinate in your garden.
What not to compost
Typical things that you can‘t compost include plastic, metal and glass. Recycle those.
Other items to avoid include meat-eating animal (dogs and cats) waste, bones, dead animals, dairy products, meats, and fats. Don't compost fossil fuels, paint, pesticides, or harsh chemicals such as bleach.
Also: Never compost invasive plants, diseased plants, poison ivy, or weeds with many seeds.
Photo by Joi Ito
How to compost
The short answer is: Make a pile of any acceptable materials and keep an eye on it.
The long answer is: Start with some bulky limbs on the bottom so that air will flow up under the pile into it. Layer enough brown materials on top so that they cover the limbs. Six or 8 inches will probably do. Spray this layer with a little water. Add green materials in a 6- to 8-inch-deep layer. Then add a layer of soil. You can also add some fertilizer, such as a 10-10-10 if you want, but don't have to. Then continue with the layering until the bin is full or you run out of materials.
In about two weeks, the contents will have settled to about half their height. It's time to turn it to introduce more air in the pile. Don't worry about the layering this time. You want a good even mixture going back in. If you have new materials to add, throw them in the mix. (If you want to add table scraps to a full bin, just burrow 8 or 10 inches in the stuff, drop them in, and cover them.)
How often you turn the pile is up to you. You don't want to do it every day, and not once every six months. Give the bacteria in the pile time to heat and cool the pile. Any time after it's cool again is a good time to turn it.
Eventually, you'll notice that there is more and more decayed material and less and less recognizable material and the pile quits heating up. That means it's done. However, if you want an ongoing pile, just keep adding more greens and browns to it and sort out what you want to use as you need it.
If your compost smells, watch the green materials-too much will be too wet and smell foul after a short while without some air flow. To prevent this, add more brown materials and disperse them evenly throughout the pile.
Or, turn your pile to add air. (The smell is caused by anaerobic decomposition. That‘s decomposition without oxygen, much like the fermentation of yeast used in making bread. You want aerobic decomposition, or decomposition with oxygen). If you dump a wheelbarrow full of cabbage leaves on a relatively small pile, then it‘s gonna smell one way or the other. Use common sense and bury any additions you make to the pile.
Circular fence or silo bin. Home improvement stores, feed and seed stores, and agricultural supply stores sell various types of wire fence in rolls of varying lengths. (Not chain link fence, but agricultural livestock fence.) It may look expensive, but if you go in with some friends, you can all have bins from the same roll.
I don't advise chicken wire: It's too small and flexible, and the compost will bulge the wire and get stuck. Start by cutting about a 10-foot piece, leaving wire sticking out on the end and make a hoop with it. Crimp the loose wires or use tie wraps or something to bind the ends together. This should give you about a 3-foot-diameter hoop.
Pallets. Pallets are cheap. (Free in many cases.) They are good to use for your first bin so you‘ll know whether you want to seriously pursue composting. Pallets don‘t look great, and they‘ll rot and attract termites eventually, but you‘ll get a feel for composting without much of a monetary investment. My advice is to have at two least side-by-side pallet bins (using a total of five pallets). Make a three-wall structure, then add another back and side wall using one pallet as a center dividing wall. The idea is to create the pile in one bin using layers as above, then toss it back and forth to turn it. You could add a third bin to put completed compost in if you get serious about it.
Barrels and tumblers. If you have a small yard, and want a little compost fast with little effort, this is the one for you. The commercial ComposTumbler on a stand the most expensive of these options. If you have an old barrel with a cap (plastic or metal), you can make your own. Just drill a bunch of ½-inch holes in the barrel. Then stand the barrel on its end and fill it and cap it. Knock it over and push it around the yard once every other day or so. Water it once in a while. In a few weeks or months, you‘ll have finished compost. You can add more materials to this one as needed. If you don‘t know where to get a barrel, try a trashcan. If you get one on wheels, you can use it to make your compost in and wheel the finished product to the garden or potting shed for easy use.
Do you need a bin?
No. It‘s a matter of personal preference. Bins keep your contents together when the wind blows, though. Bins also look nicer in some situations than a pile of dead leaves and grass. Bins, depending on the type, might be able to keep rodents out, too. And, the bins might encourage you to get out and turn your compost since you invested the time and money into creating one. If you have the room, and don‘t mind a few loose leaves blowing, and appearance isn‘t paramount to you, you don‘t need a bin.
Compost pile placement
Look at your property. You don't want a compost bin too far from the house and garden, yet not right next to them. You want it close enough that you‘ll actually use it, but not so close that it‘s an eyesore.
You can compost in either full sun or full shade. Full sun will dry the pile out faster, so you‘ll have to keep it watered. Conversely, in full shade, it will not dry out as easily, so you‘ll need better air circulation or to turn it more often.
It‘s so good, and there are so many ways, that I can‘t list them all here! But here are some of the more popular ways.
Soil amendment: Most soil benefit from extra organic matter. Either till it in or use it as a top dressing to help provide nutrients and tilth to the soil. Incompletely finished compost will provide more drainage in compacted soils than finished compost. Bigger particles, better drainage. But any compost is better than no compost.
Mulch: If you just have so much compost that you don‘t know what to do with it, use it to mulch around plants. Incompletely finished compost works for this too.
Compost tea: Take a handful of finished compost, put it in a sock or leg of panty hose, and soak it in a bucket of water over night or for a few days. Use the water to water houseplants or other potted plants. Also good for watering special garden plants. Proportions are irrelevant. The stronger you make it, the more nutritive value it will have.
Photo by Diana House
Compost has a lingo all its own. Green, brown, hot, finished. What are they talking about? Here are some definitions:
Brown: It's not just a color. Brown materials are rich in carbon and provide food for microorganisms. Common examples are dried fallen leaves, hay, or straw.
Cold-temperature: This referrs to a method of slow composting. With the cold method, you pile your materials and let them set until you are ready to use them. No turning required. It's called cold because the pile doesn't routinely heat up very much. It can take several years to get finished compost from a cold process. Most cold piles are used in an unfinished state.
Finished: State of compost when none of the original contents of the pile are recognizable. It resembles a bunch of soft brown dirt, much like lightly dampened coffee grounds.
Green: It's not just a color, either. Green materials are rich in nitrogen and provide food for the microorganisms that break down the materials. Examples are fresh grass clippings and chicken manure.
Heap: Pile of contents in or not in a bin.
Hot: It's a temperature condition as well as an ingredient condition. A compost pile will heat and cool as the microorganisms break down materials. During their feast, the pile may get as hot as 160 degrees F. Hot also describes the relative amount of nitrogen in fresh manure. The more nitrogen, the hotter it is said to be. Chicken manure is said to be the hottest manure commonly available. The word "cold" is not used to refer to materials without much nitrogen. They're just not so hot.
Tilth: Workability of the soil. More tilth is better. More organic matter provides this.
Master Composter, mastercomposter.com.