Compost

Creating and applying compost is one of the very best things a gardener can do for their soil.

Compost pile on concrete

Composting is the natural process by which organic materials are broken down, making them available to plants and microorganisms. It is a major component of pedogenesis, or soil creation. Without healthy soil, we begin to lose our food, water and air. Yeah, it’s kind of important.

More benefits of composting include:

• Less biodegradable materials end up in landfills
• Improves soil structure
• Reduces water consumption
• Reduces compaction and the need for aeration
• Improves permeability
• Reduces the use of carbon fuels
• Promotes soil fertility
• Stimulates healthy root development
• Reduces erosion
• Reduces the need for chemical fertilizers

One of the nicest things about composting is that bacteria and fungi do most of the work for you! Other organisms, such as worms and insects, also pitch in to help. Now, it is possible to simply dump everything in a pile and wait for nature to takes its course. Eventually, there would probably be a nutrient rich soil amendment, but it might take years. Or it can turn into a stinky, rotten mess. Follow these tips for successful composting in a reasonable amount of time.

Selecting a site for composting

• Place it close enough to the garden be convenient, but not bothersome.
• Avoid locations that are next to a house, fence, or other structure. Moisture and bugs do happen.
• The location can be on dirt or cement, in shade or sun If the compost pile is on dirt, that spot is going to provide some excellent growing in the future!
• The ideal size is a 3' cube, give or take. Smaller piles have a hard time getting warm enough. Larger piles tend to run out of air and are harder to flip.

Composting bins (Antranias) Public Domain

Bins, drums or piles?

Catalogs and garden centers urge you to try their latest and greatest rolling drums. Personally, I think they are a waste of money. Those bins rarely work as well as advertised and you still need to move the materials around. Closed drums are also more prone to excess moisture, which can lead to rot.

Drawing of compost bin (USDA)

Wire bins work well and are highly mobile. You simply move the wire away to flip the pile and pitch the material back in, watering as you go. If you look online or in your local library, there are many DIY compost bin instructions available for free and these simple structures do not require a contractor's license or skill set to build. For me, I find that simple piles work the best. I keep my regular compost pile near my chicken coop, for convenience. Occasionally, I move it to an exhausted bed for a season to supercharge it with nutrients and organic material.

Chickens help produce some amazing compost - plus you get eggs!

Understand the process: Organic matter + air + water = compost

Organic matter consists of yard and kitchen waste that has been cut into 2” or smaller sized pieces. Smaller pieces compost faster because there is more surface area for decomposers to reach.

Organic matter is considered either “green” or “brown”. Green matter includes cut grass, pulled weeds, kitchen scraps and manure, and it is rich in nitrogen. Brown matter is rich in carbon and includes dried leaves, straw, and shredded newspaper. The ratio of green to brown is a major factor in how long it takes a compost pile to breakdown. “Hot” piles work fastest and use a 30:1 carbon-to-nitrogen ratio, while slower piles can have a 2:1 carbon-to-nitrogen ratio. If material is continually added to a single pile, it will slow the process. A better choice is to have 2 or 3 piles, at various stages of decomposition.

Meat and dairy in the compost pile?

Most recommendations warn against using meat, dairy, and grease in compost piles. Other people have no problems with it. Personally, I use the majority of my kitchen “waste” to make soup stock. The solids are then fed to my chickens. Whatever they don’t eat (along with what they did eat) ends up in the compost pile, bones and all. I have had no problems and my plants seem to appreciate the calcium. Of course, my dogs do a very good job of keeping opossums, rats, and raccoons out of my yard. It's your call. One other method of decomposition that uses fermentation, rather than decomposition does allow you to add meat and bones without difficulty. This method is called bokashi.

Decomposition

Decomposition is an aerobic process, which means it needs air. Air helps breakdown organic matter and those tiny workers need it, too! Air enters a compost pile by turning it every few days. [Read: good exercise.]

Water is needed for the same reasons as air: it aids in decomposition and it keeps microorganisms and other decomposers alive. Keep the compost as damp as a wrung out sponge and avoid simply watering the top, as this tends to cause runoff. Watering as the piles are turned works the best. If the pile gets too wet, spread it out and let it dry, or it will rot.

Temperature is another composting factor. As materials break down, especially the green ones, energy is released in the form of heat. If you’ve ever watched a big pile of freshly cut grass, you know exactly what I mean. Under the right conditions, a pile of grass clippings can burst into flames! (And it stinks to high heaven). Ideally, the right conditions will generate temperatures between 122 - 131 degrees Fahrenheit. If temperatures remain above 140 for at least 10 days, weed seeds and pathogens will be killed. If temperatures stay above 160, however, decomposers will die and the process will stop.

Because temperature is a factor, do not expect much out of a compost pile in winter. Material can still be added, or another pile started. In spring, the whole process will begin again. Also, if an area is especially hot or wet, cover the compost pile to maintain desirable moisture levels. Some people take composting very seriously and monitor temperature. I didn’t until I started composting the bedding from my chicken coop.

Composting manure

Animal bedding and manure are reasonably good sources of nitrogen and organic material, but they can make you sick. To be safe, manure must be composted for at least 45 days, 15 of which must be at temperatures between 131°F and 170°F, and turned at least 5 times. Assuming it hasn’t been recontaminated by air-dropped bird poop or other pathogens. Raw manure should never be applied to the soil while plants are growing. If it is, be sure that the manure does not touch the plants. Composted manure and bedding have significantly improved my soil health and helped to reduce compaction. Apparently, all those earthworms and burrowing beetles love the stuff!

A steaming compost pile in the morning makes this gardener very happy!

​When is compost ready?

Compost is called “finished” when it is ready to use. There is simply no way to say how long finishing will take because of the factors already mentioned. Generally, speaking, under reasonably good conditions, a compost pile is ready for use within 45 to 60 days. Finished compost takes up 25-40% of the original occupied space, depending on its ingredients. Compost can be dug into beds before planting, a 2” layer can be applied over lawns as an amendment, or it can be used as mulch or top dressing. I like to add just a little compost to the bottom of potted plants before adding high quality potting soil and my plants seem to like it a lot.

Composting with worms

For those who do not have space for a compost pile, bin, or drum, try composting with worms! This is called vermiculture. Worm bins can compost an amazing amount of yard and kitchen scraps pretty quickly. Did you know that worms can eat their body weight in scraps every single day? Learn how to build worm bins and compost with worms at the UC Agriculture and Natural Resources page about worms.

Remember, composting is easy and it provides a powerful boost to the garden. Start composting today!