How to Make Compost for Your Vegetable Garden

1 comment Jun 14, 2021by Juanita Schulze

Vegetable peels, coffee grounds and fallen leaves can become something valuable for your garden instead of going into the trash. Composting brings those materials together with moisture and air so decomposers can turn them into a useful soil amendment.

Finished compost can improve soil structure, support soil life and help soil hold moisture. It also contributes nutrients, although it is not a complete fertilizer or a guarantee that your garden will never need supplemental watering.

A Composting Lesson That Started in Childhood

When I was a child, my dad grew a vegetable garden and kept a large metal drum in the yard for compost. He taught me to collect kitchen scraps, add them to the drum with soil and stir the mixture. Preparing compost became part of our year-round garden routine.

That simple job helped me see kitchen leftovers differently. What looked like waste could help us grow tomatoes and cucumbers in the next garden. Today, I would put more emphasis on balancing leafy and woody materials with the scraps, and on making sure the container has enough airflow.

The Four Essentials: Browns, Greens, Water and Air

A useful home composting system needs carbon-rich materials, nitrogen-rich materials, moisture and oxygen. Gardeners often call the first two groups “browns” and “greens,” but the names describe their role rather than their actual color.

Browns provide carbon. Examples include dry leaves, small dry plant stalks, shredded plain cardboard and suitable non-glossy paper.
Greens provide nitrogen. Fruit and vegetable scraps, fresh grass clippings and used coffee grounds are common examples. Coffee grounds count as greens even though they look brown.
Moisture supports decomposition. Aim for a damp-sponge feel rather than a soaking-wet mixture.
Air keeps the process aerobic. Turning, mixing and including materials that resist matting help air move through the pile.

Keep a supply of dry leaves or other browns near the bin. Kitchen scraps alone tend to create a wet, compacted mixture rather than a balanced pile.

What Can Go into a Backyard Compost Bin?

Good starting materials include vegetable trimmings, fruit peels, apple cores, melon rinds, coffee grounds and paper coffee filters. Crushed eggshells can be included, although they break down slowly.

For browns, use dry leaves, shredded plain cardboard with tape removed and suitable uncoated paper. Avoid glossy coatings, plastic labels and packaging that contains materials you cannot identify. Chop tough stalks and large scraps into smaller pieces to help them break down more readily.

Keep the following out of a basic home pile:

Meat, fish, bones, dairy products, oils and grease.
Pet waste and cat litter.
Treated or painted wood.
Diseased plants, heavily pest-infested material and weeds carrying mature seed.
Grass or plants treated with herbicides that could affect the finished compost.
Produce stickers, plastic and glossy paper.

Cooked foods can attract animals, especially when they contain fat, meat or sauces. For a straightforward beginner system, stick mainly to raw plant scraps and appropriate yard materials.

Collect Kitchen Scraps Without Inviting Fruit Flies

We have used both a bowl and a lidded pottery container on our kitchen counter. Emptying the container frequently and washing it between uses helps keep the routine manageable. If scraps need to wait longer, a closed container in the refrigerator or freezer can be useful.

A countertop collection container is not necessarily a composter. Its job may simply be to hold scraps until they reach the outdoor system. Decomposition involves microorganisms, so a clean-looking container is not bacteria-free. Wash your hands after handling scraps and keep food-preparation surfaces clean.

Do not assume a bag labeled biodegradable or compostable will break down in your backyard bin. Many compostable bags and food-service items need commercial composting conditions. Unless a product is specifically suitable for your home system, empty the scraps into the bin and keep the bag out.

Choose a Bin or Pile You Can Manage

Choose a well-drained, accessible spot near a water source. A simple contained pile, a ventilated bin or a compost tumbler can all work. Where rodents or other animals are a concern, use a suitably designed, securely enclosed system while maintaining the airflow it needs.

Do not seal an ordinary compost bin airtight. The organisms doing aerobic composting need oxygen. Choose materials and a container appropriate for the job rather than reusing a vessel that may have held harmful chemicals.

We have used large tumblers shaped like wheels on rollers. Turning them by hand makes mixing convenient, but the balance of ingredients and moisture still matters. More spinning cannot compensate for an overloaded, soggy mixture.

Build and Maintain the Mix

Start with air space. For an open pile, a loose base of suitable coarse browns can help drainage and airflow. For a manufactured bin or tumbler, follow its setup instructions.
Add greens with plenty of browns. Cover fresh food scraps with dry material and mix so wet clumps do not build up.
Check moisture. Add water gradually if the contents are dry. Add dry browns and improve drainage if the mixture is soggy.
Turn or mix when needed. Bring outer material into the active center and loosen compacted areas. Avoid treating a fixed turning schedule as a substitute for observing the pile.
Let a batch finish. Continually adding fresh scraps makes it harder to obtain uniformly finished compost. A second bin or separate curing area can help.

You do not need to add a layer of garden soil every time you add scraps. Heavy soil layers can make the mixture dense. A balanced mix already provides a place for decomposers to work, and routine additions of fish fertilizer are not necessary.

Troubleshooting Odors, Slow Breakdown and Ants

Strong unpleasant odors often point to excess moisture, too many greens or inadequate air. Mix in dry browns, loosen compacted material and check drainage.

Slow breakdown may result from dry conditions, large pieces, a small pile, cold weather or an unbalanced mix. Adjust what is actually limiting the process rather than adding fertilizer automatically.

Ant activity can occur in a dry or undisturbed pile. Check moisture and mix the contents when it is safe to do so. If you suspect fire ants, keep children and pets away, avoid disturbing the colony and seek local Extension advice. Do not add homemade borax, detergent or other pesticide mixtures to compost intended for your vegetable garden.

How to Tell When Compost Is Ready

Finished compost is generally dark, crumbly and earthy-smelling, with most of the original ingredients no longer recognizable. Some woody pieces may remain and can be screened out and returned to another batch.

A hot pile is actively decomposing; heat alone does not establish maturity. A reading of 120°F is not a universal readiness test or proof that all weed seeds and pathogens have been destroyed. Cooler composting systems can also work, usually more slowly.

Allow a finished batch to cure. It should not reheat substantially after mixing when moisture is appropriate. If you are uncertain about maturity, let it age longer or seek local guidance before putting it near young roots.

Using Compost in the Vegetable Garden

Use mature compost as a soil amendment or top-dressing, with the amount guided by your soil, the compost and the crop. There is no single 25-to-75 mix that suits every garden.

Compost alone is generally not a complete seed-starting or container-growing medium. Immature compost, excessive soluble salts or unsuitable application rates can harm plants, but it is not accurate to say that all compost automatically burns roots.

For further guidance on ingredients and backyard methods, read the EPA's home composting guide. Start with a manageable system and adjust as you learn how your materials and climate affect it.