Texas A&M AgriLife experts agree, composting helps to make gardens and landscapes healthy while helping homeowners manage waste.
Composting is fostering the decomposition of organic matter — like certain kitchen scraps and landscape clippings — until it breaks down into the rich, crumbly brown material known as compost. This nutrient-rich mix helps garden and landscape plants thrive when added to the soil.
At the same time, creating compost could help Texans divert as much as 30% of the garbage entering landfills, said Skip Richter, Texas A&M AgriLife Extension Service horticulture agent and host of Garden Success, KAMU FM/HD-1, in Brazos County.
“It’s an easy way to cultivate a healthy landscape and reduce organic waste. Plus, composting is so easy a kid can do it,” Richter said, referring to his AgriLife Extension free composting guide for kids.
How to build a compost pile
Composting is maintaining an ideal temperature in a pile of organic material as it breaks down. That pile needs a certain carbon-to-nitrogen, or C:N, ratio to do its work — 30:1 or close to it, said Joe Masabni, Ph.D., AgriLife Extension vegetable specialist in Dallas.
A publication by Masabni and AgriLife Extension assistant Patrick Lillard offers deeper information on composting, including C:N ratios for specific organic materials.
But Daniel Cunningham, Texas A&M AgriLife horticulturist with the Water University program, Dallas, says a good rule of thumb is to think of higher-carbon materials as drier and mostly brown in color. Those include items like dead leaves, dry tree mulch, newspaper and cardboard.
“On the other hand,” he said, “think of nitrogen as mostly green material, like fresh grass clippings or vegetable waste from the kitchen.”
Cunningham recommends a “brown-to-green” ratio of around 2:1 by volume generally, but exceptions occur. Coffee grounds, for example, are a nitrogen source that is brown. The Dirt on Composting, free from AgriLife’s Water University program, covers an array of composting best practices and organic materials in greater depth.
Masabni recommends building a compost pile of three repeating layers of organic material, up to 5 feet tall, with a minimum footprint of 3 square feet.
“Ideally you want about 4 square feet to create a stable environment for the microorganisms that break it all down,” Masabni said.
Add the coarsest organic materials as the bottom layer, and the finest as the top layer in each set of three.
Temperature is key in composting
The pile should become a literal hotbed of activity as microorganisms feverishly consume the organic material, turning it all into compost.
Temperatures within a well-functioning compost pile will reach between 135-165 degrees, Cunningham said. Hotter temperatures could cause microorganisms to die off, halting compost production.
“Compost piles sometimes overheat when adding in too much nitrogen,” he said, also recommending a compost thermometer to monitor the heat. “At the same time, too much carbon, excess dryness and forgetting to turn your pile can slow down the process, too.”
Mixing up the layers at least every 10-14 days, by turning a compost pile, will keep microorganisms at work by circulating critical oxygen through the pile.
Richter recommends adding moisture to the pile while building each layer, and to maintain moderate moisture when turning the pile.
“Only a few drops of water should drip out when you squeeze a handful of properly moistened compost,” he said.
The finished product
Finished compost should be a dark, finer material resembling a somewhat coarse but rich soil.
“The compost resulting from a well-maintained compost pile should smell earthy and fresh,” Richter said. “Excessive nitrogen can result in an ammonia odor, while offensive odors such as rotten food may indicate soggy conditions and require additions of more dry material.”
Conversely, the experts said, signs of too little nitrogen or water include organic material remaining intact in the pile, a pile that is too cool or a pile that is only warm in the very center.
Finished compost can be mixed into the soil or added regularly as a top-dressing, depending on an array of soil conditions.
The right amount of compost
“’How much do I need?’ It’s a question I get all the time from gardeners interested in making their own compost,” Masabni said.
A 3- by 3- by 3-foot compost pile will cover a 4- by 8-foot bed with an ideal 3 inches of compost once per year. Compost is also available from some local governments, recycling centers and retailers.
Composting guide links
Visit the publications in this story and other Texas A&M AgriLife online materials for comprehensive guidance on composting, compost troubleshooting and resource-efficient landscaping and gardening in Texas.