Beginner’s Guide to Making Compost: Organic Gardening

By: Willi Evans Galloway

Nature creates compost all the time without human intervention. But gardeners can step in and speed up the composting process by creating the optimal conditions for decomposition: Air + Water + Carbon + Nitrogen = Compost

Air. Like most living things, the bacteria that decompose organic matter, and the other creatures that make up the compost ecosystem, need air. Compost scientists say compost piles need porosity—the ability for air to move into the pile. I like to think of porosity in terms of fluffiness. A fluffy pile has plenty of spaces—or pores—for air to move about. A flat, matted pile of, say, grass clippings does not. Even fluffy piles compress during the composting process. Occasionally turning your pile refluffs the material, moves new material into the center, and helps improve air flow into the pile, says Craig Cogger, Ph.D., extension soil scientist at Washington State University.

Water. Compost microbes also need the right amount of water. Too much moisture reduces airflow, causes temperatures to fall, and can make the pile smell; too little water slows decomposition and prevents the pile from heating. Conventional wisdom says that compost should feel like a wrung-out sponge, says Abigail Maynard, Ph.D., agricultural scientist at the Connecticut Agriculture Experiment Station.

Carbon ingredients. The microbes that break down organic matter use carbon as an energy source. Ingredients with a high percentage of carbon are usually dry and brown or yellow in color. The most common high-carbon ingredients are leaves, straw, and corn stalks. Sometimes people call these ingredients browns.

Nitrogen ingredients. Microbes need nitrogen for the proteins that build their tiny bodies. Ingredients high in nitrogen are generally green, moist plant matter, such as leaves, or an animal by-product, such as manure. These ingredients are called greens, but in reality they can be green, brown, and all colors in between.

C/N ratio. In order for a compost pile to decompose efficiently, you need to create the right ratio of carbon (C) to nitrogen (N) (C/N). Piles with too much nitrogen tend to smell, because the excess nitrogen converts into an ammonia gas. Carbon-rich piles break down slowly because there's not enough nitrogen for the microbe population to expand. An ideal compost pile should have a 30:1 C/N ratio. Grass clippings alone have about a 20:1 C/N ratio. Adding one part grass clippings, or other green, to two parts dead leaves, or other brown, will give you the right mix.

Building a Compost Pile
There are two main ways to make compost: cold compost (minimum effort) and hot compost (maximum effort).

Cold Black Gold
Nearly every expert I talked with admitted (sometimes sheepishly) that they do this type of composting in their own back yards because it’s easy. Here’s how to make cold compost: Mix together yard wastes, such as grass clippings, leaves, and weeds, place them in a pile, and wait 6 to 24 months for the microorganisms, earthworms, and insects to break down the material. Add new materials to the top of the pile. You can reduce the waiting period by occasionally turning the pile and monitoring and adjusting the pile’s moisture level. The compost will be ready when the original ingredients are unrecognizable. Generally, compost on the bottom of the pile “finishes” first. You may not want to include woody material, because it breaks down too slowly.

Pros: Takes little effort to build and maintain; can be built over time.
Cons: Takes up to 2 years to produce finished compost; doesn’t kill pathogens and weed seeds; undecomposed pieces may need to be screened out.

Some Like It Hot

Hot, or fast, composting takes more work and the right combination of ingredients, but you can get high-quality compost in under 2 months. Here’s how: Wait until you have enough material to create compost critical mass (27 cubic feet), which is the minimum volume for a pile to hold heat. Then mix one part green matter with two parts brown matter. Bury any vegetative food scraps in the center to avoid attracting animals. Check to make sure the mixture has the ideal moisture level. Continue adding mixed greens and browns and checking the moisture until you’ve built a pile that is 3 feet by 3 feet by 3 feet, or 5 feet wide at the base and 3 feet wide at the top. The microorganisms will immediately start decomposing, and their bodies will release heat. The pile will insulate the heat, and the temperature of the pile’s interior will reach 120°F to 150°F. Turn the pile weekly and regulate moisture levels. After about a month, the hot phase will be done, and the pile will finish decomposing at temperatures between 80°F and 110°F. The compost will be ready to use when it no longer heats and all of the original ingredients are unrecognizable.

Pros: Produces high-quality compost within 2 months (and sometimes as soon as a few weeks); can kill weed seeds and pathogens. (Organic Gardening does not recommend adding weed seeds or manures that contain human pathogens to compost—hot or cold—because uniform heating is difficult to achieve in home compost piles.)
Cons: Time-consuming; requires careful management of moisture, air, and C/N ratio.

Source:http://www.organicgardening.com

Compost Tips for the Home Gardener

What Is Compost?

Compost is a dark, crumbly material created when microorganisms break down organic matter such as leaves, grass clippings and kitchen waste. Compost is not completely decomposed (like humus); it will contain small pieces of debris that can be recognized as bits of twigs and leaves.

Why Compost?

Converting yard debris to compost has many benefits. It is an environmentally friendly way to reduce the amount of solid waste that must be disposed of, and it provides useful and beneficial products for yards and gardens. Compost is an excellent soil amendment that improves the health and structure of both sandy and clay soils. It can be applied on top of soil as mulch. Mixed with other components, it makes a good potting soil and some gardeners brew it in water to make a compost “tea” for plants.

What Can Be Composted?

Two types of materials are needed for successful composting: “green” materials, which are rich in nitrogen, and “brown” materials, which are rich in carbon. Table 1shows the types of materials that are considered “browns” and “greens.

Twigs and branches greater than 1/4 inch in diameter and fibrous palm fronds should be processed in a shredder/chipper before composting. Leaves, especially waxy types such as live oak, laurel oak, water oak, and magnolia, also break down faster if they are shredded. Sawdust and other wood scraps can be composted, but they take a long time to decompose.

Keep seed-laden weeds, diseased plants and nematode-infested roots out of the compost pile since it is difficult for most home composting units to reach the high temperatures (130-140°F) needed to destroy these pests. Meat, bones, and foods with oils, dressings, or fats, should not be composted because they may attract animals or produce an objectionable odor. The manure of animals that eat plants (cows, horses, etc.) is a great “green” material for a compost pile. However, carnivorous animal waste (dogs, cats, etc.) should not be used due to the possibility of diseases.

Building a Compost Pile

Composting is all about supplying the microorganisms that do the decomposing with the essentials of life: food, water and oxygen. Microbial activity is affected by the proportion of carbon (brown materials) to nitrogen (green materials). This is commonly referred to as the “C/N ratio.” The optimum C/N ratio for rapid composting is about 30/1 or less. Table 2 lists the approximate C/N ratio for materials commonly used for composting.

A compost pile or unit should be sited in an area protected from drying winds and where it can be reached with a hose. Place it in a shaded area where you will be more comfortable when you “work” it. Depending on what type of compost “unit” you buy or build, you may want it screened from view by neighbors and yourself. Keep in mind that there is nothing magical about commercial compost units; they are simply holding units and will not produce compost any faster or better than a simple pile. The most important feature is that the pile or unit be a minimum of 3' x 3' x 3'. Refer to Fact Sheet AE23 “Construction of Home Compost Units” for more information. It is available on the web:

http://edis.ifas.ufl.edu/HE026 http://solutionsforyourlife.ufl.edu/map/

To create the compost pile, layer roughly equal amounts of “green” materials and “brown” materials in alternating 3- to 4-inch tiers up to a height of about 3 feet. Smaller particles will decompose faster than larger materials. It is essential that each layer be watered as you build the pile; otherwise it is almost impossible to moisten the center of the pile once it is completed. The materials should be moist, not soggy. There is no advantage to purchasing a compost “starter,” since organic yard wastes naturally contain the microorganisms needed to start the decomposition process.

Managing a Compost Pile

A new pile of green and brown materials will heat up rapidly. This is a reflection of the microbial activity. After 4-7 days, it will begin to cool and should be turned at this time to mix the materials and allow the pile to heat again. A hot pile will often produce steam, but this is nothing to worry about. Compost can be produced fairly rapidly (about six weeks) if the pile is occasionally turned and watered (if dry). Turning also shifts material from the outer (cooler) part of the pile to the warmer center. It may be necessary to add more water during the composting period if the pile appears dry. Materials added to a compost pile or unit which is not turned or watered will still decompose. It will just take much longer.

If you are interested in monitoring the temperature of the pile, use a long-stemmed compost thermometer that reads to 160° F or higher. The most effective range for composting seems to be 122°F - 131°F. Higher temperatures of 131°F - 140°F may be desirable to destroy weed seeds or plant pathogens, but it is difficult to maintain a pile at that temperature. At temperatures above 149°F many of the organisms involved in composting become inactive or die. If the pile becomes too hot, decrease the intervals between turnings.

How to Use Compost

Compost is ready to use when it is dark brown and crumbly. If the texture is not uniform, the compost can be sifted through a screen to remove larger pieces, which can then be returned to the pile for further composting.

Compost is a wonderful soil additive – especially to Florida's poor, sandy soils. Use only finished compost as a soil amendment. Otherwise, microorganisms will “rob” nutrients from plants as they continue to decompose the unfinished compost. Add 1-3 inches of compost to the soil surface and mix it to a depth of 4-6 inches. Compost can also be used as mulch. This is a particularly good use of unfinished compost. It will continue to break down, and, like all mulches, will need to be re-applied once or twice a year. As a potting mix, use only finished compost and blend it with a material that improves the drainage of the mix such as coarse sand, perlite, or vermiculite.

Compost contains small amounts of nitrogen and micronutrients which can be extracted for a plant “tea.” Fill a bag made of cheesecloth, burlap or some other woven fabric with compost and soak it in a bucket of water for one hour. Use the resulting tea as a weak, liquid fertilizer.

Troubleshooting a Compost Pile

Table 3 provides information on common composting problems, their causes and how to solve them.

References

1. Sydney Park Brown. Yard Trash to Garden Treasure, Horticulture and Water Management, Hillsborough County Cooperative Extension Service, Sponsored by Hillsborough County Solid Waste Department.

2. Roger A. Nordstedt and Anne W. Barkdoll. 2003. Fact Sheet AE23 Construction of Home Compost Units. Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida.

3. Roger A. Nordstedt and Anne W. Barkdoll. 1991. Circular 958 (available only via CD-ROM), Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida.

4. Florida's Online Composting Center. Sarasota County Government Environmental Services Business Center Solid Waste Division, Resource Conservation Section, http://www.compostinfo.com/

Source: Gardening Guide

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