Horticulture/Compost Introduction

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All organic matter eventually decomposes. Composting speeds the process by providing an ideal environment for bacteria and other decomposing microorganisms. The final product, humus or compost, looks and feels like fertile garden soil. This dark, crumbly, earthy-smelling stuff works wonders on all kinds of soil and provides vital nutrients to help plants grow and look better.

Decomposing organisms consist of bacteria, fungi, and larger organisms such as worms, sow bugs, nematodes, and numerous others. Decomposing organisms need four key elements to thrive: nitrogen, carbon, moisture, and oxygen. For best results, mix materials high in nitrogen (such as clover, fresh grass clippings, and livestock manure) and those high in carbon (such as waste paper, dried leaves and twigs). If there is not a good supply of nitrogen-rich material, a handful of general lawn fertilizer will help the nitrogen-carbon ratio. Moisture is provided by rain, but you may need to water or cover the pile to keep it damp. Be careful not to saturate the pile. Structuring the pile to maintain small air spaces provides oxygen. Frequent turning yields faster decomposition.

Common Problems

Can use tarp to cover top of compost

Composting is not an exact science. Experience will tell you what works best for you. If you notice that nothing is happening, you may need to add more nitrogen, water, or air. If things are too hot, you probably have too much nitrogen. Add some more carbon materials to reduce the heating. A bad smell also may indicate too much nitrogen, or too little air.

Cold composting often proceeds faster in warmer climates than in cooler areas. Cold piles may take a year or more to decompose depending on the materials in the pile and the conditions.

Hot Composting requires more work, but with a few minutes a day and the right ingredients you can have finished compost in a few weeks depending on weather conditions.

Adding kitchen wastes to compost may attract flies and insects. To prevent this problem, make a hole in the center of your pile and bury the waste.

Ingredients

All composting requires three basic ingredients:

Browns - This includes materials such as dead leaves, branches, chopped twigs and straw. Provide the carbon (C).
Greens - This includes materials such as grass and hedge clippings, plant cuttings, flowers, vegetable waste, fruit scraps and other scraps, and coffee grounds. Provide the nitrogen (N).
Water - Having the right amount of water, greens, and browns is important for compost development.

Your compost pile should have an equal amount by volume of browns to greens (the ideal C:N range). You should also alternate layers of organic materials of different-sized particles. The brown materials provide carbon for your compost, the green materials provide nitrogen, and the water provides moisture to help break down the organic matter.

Cover top of compost with a tarp to keep it moist.

Tools

A pitchfork next to a compost bin

Tools include pitchforks, square-point shovels or machetes, and water hoses with a spray head. Regular mixing or turning of the compost and some water will help maintain the compost.

Using Compost

Compost can be used for all your planting needs. Compost is an excellent source of organic matter to add to your garden or potted plants. It helps improve soil structure which contributes to good aeration and moisture-holding capacity. Compost is also a source of plant nutrients.

Compost can also be used as a mulch material. Studies have shown that compost used as a mulch, or mixed with the top one-inch layer of soil, can help prevent some plant diseases, including some of those that cause damping of seedlings.

Adapted from the USDA Backyard Conservation Tip Sheet, and EPA Composting At Home public-domain works of the US Government.