Q: Is there a certain soil type best for composting? The soil near my home is mainly sand/clay (Arizona's high desert, Four Corners region). How can I best help the composting process taking into account the amount of sun, wind and water received in my region? What is the most sustainable way to do so?
Asked by Dianne Nakai, '03, Window Rock, Ariz.
Recently, I toured a community farm with an immense composting area. Multiple piles were placed in a special order based on the method and materials used for composting. Our tour guide explained the complex turning and layering techniques of each pile: I stared in amazement at what I had assumed was simply about rotting banana peels. Luckily, composting in your own backyard doesn't have to be complicated for it to be successful, even if your hometown's soil and climate are extreme.
Adding compost to any soil increases the amount of oxygen and water the soil holds, making it better for plant growth. More extreme soils, such as sand or clay, benefit more from compost than other soils—good news for places like Arizona. The process of composting in a desert climate, however, may require more TLC than in milder environments.
Temperature and moisture are the composting factors most affected by climate. Healthy compost piles may get as hot as 140 degrees Fahrenheit early in the process; heat speeds up the decay process. The outside air temperature also affects compost. Desert days are warm enough for decomposition to occur, even in winter. However, at night—especially in winter—temperatures in the desert fall below freezing. This can stop the decomposition process. Covering your compost pile with a tarp—or better yet, using a black container positioned in the sun—will ensure your compost survives the night.
As for moisture, an ideal compost pile is 40 to 60 percent water. That means the material should feel about as wet as a wrung-out sponge. In the Arizona high desert, where it is very dry, particularly in the spring and fall, you will need to pay extra attention to your compost pile's moisture content, and you will almost certainly have to water it to keep it active. (You can choose not to water your compost pile at all. You'll still get good compost, it will just take longer.)
Watering compost brings up a sustainability issue—is frequently watering in an area that often experiences extreme drought conditions environmentally justified? Keeping your compost pile covered with a tarp or in a container will retain more moisture, so it will work longer on just the moisture from your food scraps. You can also choose to landscape your yard with native plants, which are adapted to the dry climate and sand or clay soils. Although natives would still benefit from compost, they might need less of it in the long run. That means you could keep a smaller compost pile and put in less water. I suggest keeping a container in the bathroom to catch the cold water in the shower while you wait for it to heat up. My parents are passionate water-saving advocates, so I grew up doing this in the Bay Area. We used the water on our plants. It sounds intense, but it really adds up.
All it takes when it comes to composting, or what Eliot Epstein in The Science of Composting calls "the highest form of recycling," is being mindful of your region's environmental conditions. With that awareness, nothing should stop you from creating a pile of healthy, decomposing material that's great for the earth.
Gretchen O'Henley received her bachelor's degree in Earth Systems in 2011.
