The Dirt on Composting

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Gardening columnist Karen Bridgewater displays some in-progress compost from her backyard tumbler. In this column, Bridgewater shares some knowledge she and her husband have gained over 25 years of composting, as well as advice from other experienced gardeners. Photo: Isabel Ebiner

By Karen Bridgewater

If you have ever tried gardening in San Dimas, the following scenario may sound very familiar: the sunbaked soil is hard as a rock, and it is nearly impossible to dig a hole. A network of cracks has formed across the ground, and when you irrigate, water puddles up on top of the surface. Nothing grows. This is our native clay soil, and it is in desperate need of organic matter, otherwise known as compost. 

What is compost, and how does it improve soil?

Compost is simply decomposed organic material, such as plant and food waste. It is rich in nutrients and beneficial organisms. Compost’s crumbly nature improves the structure of compacted soil by increasing air circulation, moisture retention and water drainage. 

Hard, compact soil makes it difficult for roots to grow and limits the amount of air and water available, which they need to survive. Compost breaks up the hard clay, providing a more hospitable environment for plants to grow. Bacteria and fungi in the compost convert nutrients in the soil into substances easily absorbed by plant roots.

Buying vs. making compost

You can buy compost in bags from home improvement stores and nurseries, purchase it in bulk from landscape supply companies or take the leap and make your own.

Creating your own compost is economical and good for the environment — plus, it is a great way to connect with nature. Purchasing compost can get expensive, especially if you are buying it in bags. Making your own from kitchen and yard waste not only saves you money but also helps to decrease the amount of debris going to the landfill.

How does composting work?

The workhorses of the composting process are microorganisms that break down organic materials. Since these microbes are living creatures, they require oxygen, moisture and food to survive. They do best in a moist, well-aerated environment and need to be fed a proper ratio of brown and green materials.

Carbon-rich brown materials — such as dried leaves, twigs, straw, sawdust, corn stalks, newspaper and cardboard — decompose slowly. Green materials are rich in nitrogen and break down quickly. These include grass clippings, coffee grounds, vegetables and fruits, fresh leaves and manure from animals like cows, horses, sheep, chickens or rabbits. 

Certain materials should not be used in composting because they are toxic or will interfere with the composting process. These include dog and cat waste, meat scraps, fats and oils, charcoal ash, diseased or chemically treated plant material, citrus and debris from black walnut and eucalyptus trees. 

How much brown and green material is needed?

It is generally recommended to add more carbon-rich brown materials to the pile, but you can experiment with various ratios of browns to greens from 1-to-1 to 4-to-1. Observe how your pile responds.

As the pile breaks down, it should have the consistency of a wrung-out sponge and smell pleasant. 

If the pile is wet and stinky, you added too many greens. Correct this by adding brown material to balance the mixture and absorb the excess liquid.  Then turn the pile to incorporate more air. 

If the pile looks dry and does not heat up, it needs water and more greens. Work both into the pile with a pitchfork to bring it back into balance.

BEGINNER’S TIP: For those new to composting, San Dimas resident Debbie Gibbs suggests a simple way to figure out the ratio of materials to use when building your pile: fill up two grocery bags, one with greens and one with browns, then dump them on the pile and mix them up.

When will my compost be ready to use?

Creating usable compost can take anywhere from two weeks to two years. 

Chopping brown and green materials into small pieces, frequently turning the pile and using a high nitrogen activator, such as blood meal, can help speed up the process. Most backyard composters can produce finished compost within two to six months.

Finished compost will be dark and crumbly and have an earthy smell. It will resemble rich soil and no longer look like the materials that were originally added to the pile.

How do I use compost to improve my soil?

If the soil can be tilled, you can spread two inches of compost on top of your planting area and mix it into the top 12 inches. However, this destroys networks of beneficial fungi that help roots access nutrients in the soil. Spreading compost on a bed in the fall and working it into the top few inches of soil in the spring is a better alternative.

Even better is to choose a method that improves the soil without digging, such as lasagna or hugelkultur composting, which will be discussed in the next section. 

Composting methods  

There are many composting techniques. Choose an approach based on your budget and lifestyle.

Traditional composting
An open pile can be built on the ground or contained in a wire cage. Closed bins can be purchased or constructed from wood. Aim for a pile that is at least 3 feet high, 3 feet wide and 3 feet deep, as the finished compost heap will reduce to half its original size. 

Place alternating layers of brown and green materials on your pile, and top it with a brown layer to cut down odors that might attract animals. 

Hot composting
If you are impatient but willing to do a little work to speed up the process, hot composting may be the method for you. 

Chop up materials before adding them to the pile to make it easier for microorganisms to do their work. Instead of layering the brown and green materials, mix them together in a large pile.

Bridgewater shows off her husband’s backyard compost pile, which is turned regularly. Photo: Isabel Ebiner

As the microbes digest the materials, heat is generated. It is critical that the pile is at least 3 feet high, 3 feet wide and 3 feet deep, otherwise it will not heat up enough to kill weed seeds and pathogens. This only occurs when the pile maintains a temperature of approximately 140 degrees for 72 hours. After that time, the temperature drops. When the temperature falls to 100 degrees, turn the pile with a pitchfork. 

This process, repeated every several days, can produce finished compost in as little as three weeks.

Lasagna composting 
Lasagna composting, also known as sheet composting, is a slow, soil-building method that involves layering organic material directly on top of the ground where you will plant.

Before starting, clear the targeted area then cover it with a thick layer of cardboard to smother weeds and keep the ground moist.

Add alternating layers of brown and green materials to at least 3 feet high, moistening each layer as it is laid down. Finish with a thick layer of mulch. Left alone, the compacted ground beneath the cardboard will transform into soft, rich soil in six months to a year.

If you are in a hurry to get growing, you can use this method directly in a raised bed, and instead of waiting for it to finish composting, top it off with a few inches of garden soil and plant right away.

Hugelkultur
Hugelkultur is a method that uses logs as a base layer to retain moisture and nutrients, followed by layers of branches, twigs, straw, manure, leaves and grass clippings.  

San Dimas resident Debbie Gibbs is having great success with this method. The dark, rich soil teeming with worms in her 5-by-8-foot raised bed is proof of that. In addition to the logs in the bottom of the bed, Gibbs added five straw bales, cardboard, leaves from her 300-year-old oak tree, green leaves, palm fronds and kitchen waste. 

To speed things up, Gibbs “blitzes” kitchen scraps in her Vitamix before pouring them down French drain pipes that are partially buried in the bed. Worms crawl through the holes into the pipes, eat the food then return to the bed to deposit their castings (worm poop). 

San Dimas resident Debbie Gibbs uses French drain pipes to feed the worms in her hugelkultur raised bed. Photo: Isabel Ebiner

During the pandemic, Gibbs focused on composting cardboard.

“I made a promise to myself that I would use all of the cardboard packaging that came to the house,” said Gibbs.

Gibbs said composting has improved the health of her plants and reduced the amount of water she uses on her garden by 75%.

Compost tumbler
A tumbler is a rotating barrel suspended by a frame and equipped with a latching door. The barrel is filled with the proper organic material blend then “tumbled” with a crank. This method aerates the compost, helping it to heat up, and increases the speed of composting. Under ideal conditions, finished compost can be cranked out in as little as two weeks.

Bridgewater’s dog Cody walks past the backyard compost tumbler, which uses a crank to turn organic material and produces ready-to-use compost in as quickly as two weeks. Photo: Isabel Ebiner

Vermicomposting
Vermicomposting, or worm composting, is a method that quickly turns food scraps into a rich soil additive referred to as “black gold.”

The basic process involves raising Red-wiggler worms in a plastic bin filled with damp shredded paper and periodically feeding them kitchen scraps.

Microorganisms in the worm’s gut digest the paper and food scraps, transforming them into nutrient-rich castings that are then harvested and used as a soil enhancement.

Bridgewater feeds vegetable scraps to the Red-wiggler worms in her vermicomposting bin. Microorganisms in the worm’s gut digest the paper and food scraps, transforming them into nutrient-rich castings. Photo: Isabel Ebiner

Paul Vander Werf, vermiculture chairperson for California Garden Clubs, said that vermicompost is more valuable and sells for “ten times more than regular compost.” It holds twice as much water as regular soil, suppresses plant diseases and pathogens, buffers soil pH and contains hormones that promote plant growth. 

Unlike a typical compost pile that quickly compacts, he said, “worms constantly move through the soil, aerating and breaking it down much faster.“

When asked how much effort it takes to make vermicompost, Vander Werf said, “You need to check it five minutes every day and feed it once every week or two. Then you just observe and learn.”

Vander Werf encourages people to start small and don’t expect perfection. Worms reproduce every 45 days, so even if some of your worms die, more will hatch, allowing you to learn from your mistakes and try again.

Sound like too much work?

If soil building seems too complicated, do not let it dissuade you from gardening. You can always plant in raised beds placed on top of the hard, clay ground, filled with potting soil.

Additional resources

To learn more about composting, check out “Let it Rot” by Stu Campbell or “Worms Eat My Garbage” by Mary Appelhof. The Los Angeles County Department of Public Works offers a free, online composting class at smartgardening.com.

Composting classes
Smartgardening.com Homepage

Basic composting
Home Composting – Garden Gold From Kitchen & Garden Waste 
Composting Basics 
Composting 101: What is Green & Brown?

Lasagna/sheet composting
Sheet Mulching 
Go From Lawn to Garden 
Sheet mulching — aka lasagna composting — builds soil, saves time 

Hugelkultur gardening
Hugelkultur gardening – Master Gardener Society of Oakland County
Permaculture, “The Many Benefits of Hugelkultur,” 
hugelkultur: the ultimate raised garden bed 

Vermicomposting
Vermicomposting 101: How to Create & Maintain a Simple Worm Bin 
Vermicomposting 101: Plant and Soil Benefits of Vermicompost 

Tumbler composting
Make Superior Compost

Sources of free mulch
Free Mulch: La Sanitation 
Mulch & Compost Giveaways

Books, equipment and accessories
Let it Rot! (book)
Worms Eat My Garbage (book)
Compost Thermometer
Stainless Steel Odor-Free Compost Pail
Compost Bins and Tumblers
Choose the Right Mantis Composter by Available Features
Order Live Composting Worms, Lowest Price Quality Composting Worms


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