While the desert can offer ideal sunshine and temperatures for many plants, desert growing can be fraught with difficulties. There’s not enough rainfall, it’s too hot, and the soil tends to be very sandy.
Thankfully all of these issues can be mitigated with compost, which can help retain moisture, insulate plant roots, and fix sandy soils.
But it’s also these very issues that can make composting challenging. In order for decomposition to occur there needs to be moisture – which is the one thing the desert doesn’t have.
Desert Composting: A Unique Process
To optimize decomposition, every compost pile needs to maintain at least 50% moisture, which should feel like a damp, wrung-out sponge. Since evaporation is such a problem in the desert, you’ll need to work harder to achieve this level of moisture. Here are some general guidelines to help you get the most from your desert compost.
- Locate your compost in the shade.
Composts located in direct sunlight will be an average of 10 to 15 degrees hotter than those in the shade. Higher temperatures speed evaporation, challenging decomposition and the microbes that help it take place.
- Minimize ventilation holes.
Enclose your compost pile in a bin with fewer ventilation holes than those designed for moister climates. This will help minimize water loss through evaporation.
- Minimize disturbance.
Gardeners who live where rain is more frequent benefit from turning their compost often, because turning speeds aerobic decomposition. In the desert, however, frequent turning can result in your pile drying out too quickly, which slows decomposition. Try to strike a balance between turning your pile and keeping it moist by minimizing turning and wetting your pile each time you turn it.
- Aerate the pile by adding dry bulk material.
Sticks, pinecones, twigs, corn stalks, and other dry, bulk materials help “fluff” up your pile by introducing air pockets to improve aeration. This is in addition to the typical brown/green ratio that a regular compost pile would have. Normally you would add at least two parts brown (carbon) to one part green (nitrogen) material. (The idea ratio is closer to 20:1 carbon to nitrogen). Brown materials include leaves, nut shells, paper towels, straw, and shredded paper. Green materials include grass trimmings, coffee grounds, food waste, and crushed eggshells. In the desert pile, add an additional layer of dry, bulky material in between each layer of green/brown material, or approximately 4” of bulking on top of each 6” of green/brown. Every now and then you can add some water if it dries out.
- Cover the pile.
Adding some kind of topper to your compost will help seal in moisture and insulate your pile from the outside. A desert compost pile will heat up very quickly from the inside and should reach 150° F for at least a few days. When it cools down, usually after a week or two, you can turn the pile. This means trying to bring the bottom of the pile to the top, and the sides into the middle. Then the pile will heat up again, and the process repeats until everything except the bulking material has turned to humus. Insulating your pile with a layer of leaves, cardboard, or straw will aid this process. An enclosed compost bin with a lid is another great option.
Setting Up Your Pile
A plastic compost bin with solid sides and a sturdy lid is the best for desert conditions. Not only does this type retain moisture, it will keep out unwanted critters that will be looking for water and food. You can make your own by drilling a few aeration holes in the sides of a large plastic garbage can, but you will also have to cut the bottom out because it does need to sit directly on the ground for friendly microbes and bacteria to move in. It also needs to be fairly large, since you have to add so many bulking materials.
A compost tumbler makes turning the pile easy, and many desert gardeners recommend the tumbler design for its ability to retain moisture.
One of the best bins for desert composting is the Eco King 160 Gallon Compost Bin, which gives you plenty of space, easy access, and UV-resistance. Coupled with a nearby rain barrel for access to moisture, and some shade, and you will have the ideal desert composting setup with little effort.
Alternatively, you can get everything in one with the Compost Wizard Hybrid Composter and Rain Barrel, which combines a 47-gallon rain barrel with a rotating composter. A compost tumbler makes turning the pile very easy, and many desert gardeners recommend the tumbler design for its ability to retain moisture. This tumbler allows water from the compost to run down into the rain barrel, but you can just as easily remove water from the barrel and put some back into the composter, not only saving water but retaining nutrients as well. Because it is black, it is also recommended to keep it in the shade because it will get very hot.
When you first set up your bin, add a layer of bulking material, a layer of food waste/carbon material, and a little bit of dirt. If your bin is open to the ground, dirt isn’t as important, but a tumbler bin needs to be inoculated with some dirt in order to introduce beneficial microbes that will kickstart the composting process.
Success in the Desert
There are other ways to achieve success when composting in the desert. Many desert gardeners find that using their compost as mulch in the garden helps things break down successfully because of the steady stream of water that keeps their compost moist. This means that you really do need to monitor the moisture content of your compost pile very frequently.
If you want to try mulch composting, one of the easiest ways is to add all of your waste in the rows between your beds, then cover with some leaves or straw. As you water the garden, the mulch will break down very quickly and you can stir it into the beds. Possibly the best system is a combination between the two – using a composter as storage and a way to start the decomposition process, and then putting the compost down as mulch before it has completely turned to humus.
Fortunately, composting isn’t an unforgiving process. You can’t ruin your desert compost – it will just dry out if it’s not working. Experiment with water, shade, and proper carbon/nitrogen ratios to find the right system for your microclimate.
By Nicole Faires