Arizona is a place of heat and sunshine, which some plant species love, but the dry conditions and hot daytime temperatures make it tough for desert gardeners. Southwest soils are often too sandy for many plants, and the lack of reliable rainfall limits plant selection for avid gardeners.
Compost can help alleviate some of the issues that Arizonian gardeners face, but the desert conditions pose a problem even here. Compost requires moisture and lots of it, but water is a resource often in short supply in the Southwest.
If you live in the desert and have attempted to turn your organic scraps into the nutrient-rich, dark, and crumbly compost plants love, you may have been frustrated by how long it takes. The dry conditions can make composting in the desert challenging, but that's because you haven't yet hit on the right formula.
Keep reading and learn how to improve your composting efforts to create fertile, loamy soil for a thriving desert garden.
What is Compost?
Compost is what you get when you decompose organic matter like vegetable scraps and garden waste. Well-made compost is a nutrient-rich soil improver that provides nourishment for growing plants.
Composting is a natural process that can take a long time in nature when left to its own devices. However, there are things you can do at home that will significantly speed up the process, which are especially handy when gardening in the hot, dry climes of Arizona.
Why Should You Compost?
The U.S. Environmental Protection Agency reports that 26% of landfill material comes from kitchen scraps and garden waste. Many Arizona cities promote backyard composting to reduce the amount of organic waste making its way into landfills.
Compost also improves the amount of water that soil can hold, and will save you money on fertilizers and soil improvers. Hard, sandy soil is difficult for roots to penetrate. They have a much easier time of it when the earth has been loosened with compost.
Composting in Arizona
Composting isn't a complicated process, but ensuring you have all the essentials in place will give you the best results.
Microorganisms from Native Soil
A couple of shovels of native soil will kickstart the composting process. This step introduces millions of bacteria and fungi to your organic waste, which are essential if composting is to occur. There are commercial products available that have these organisms, but they aren't strictly necessary.
Many of the bacteria and fungi responsible for the composting process need oxygen to survive (aerobic), but some do not (anaerobic). Both will eventually break down organic waste, but it's preferable to have the aerobic organisms doing all the work.
Regularly lift and turn the compost with a garden fork to aerate it and kill the anaerobic microorganisms. The composting will go quicker, and you'll avoid the unpleasant odors created by the anaerobic organisms.
You can help the aeration process by placing bulky material like twigs, sticks, pinecones, paper towels, and shredded paper in with the organic waste. You shouldn't have any problem filtering the twigs out when you are ready to use the compost.
Keeping your compost heap moist is one of the biggest challenges in the desert, but it's essential for keeping the microorganisms alive. The key is to keep it moist, but not wet. If the heap is too soggy, you could create a mosquito problem and will have to endure bad odors.
Try creating your compost heap in a shady location to prevent evaporation on hot Arizona days. It's possible to cover the compost and lock the moisture in, but you will want to be careful not to miss out on rainfall.
If you do decide to cover your compost heap, it will heat up internally to around 130° F to 150° F very quickly. Let the pile sit for about a week or two before turning it. Turning your compost means transferring the bottom to the top, and the sides into the middle. After you do this, it will heat up again. Eventually, all of the organic waste will have turned into humus.
An extra layer of leaves, cardboard, or straw will insulate the pile and help with the composting process, but you could also try an enclosed compost bin with a lid. Compost bins often have holes for ventilation, but in Arizona, it's a good idea to use one with fewer holes to prevent evaporation.
Most of the organic waste leftover from cooking can be added to a compost heap. Grass clippings, expired flowers, vegetable peels, cores, coffee grounds, and fruit rinds are all great candidates for the compost bin. You can also throw in sawdust, straw, and shredded paper, but keep these to appropriate amounts (more on this below).
How to Speed Up the Composting Process
Nitrogen is essential to the composting process because the decomposing bacteria and fungi rely on it for their growth and metabolism. You can ensure there is an adequate supply of nitrogen by adding green material to the heap. If there is too little green material, the composting process will be slow and may even be brought to a halt.
Carbon is also a vital component of the composting process, and you can accelerate composting by maintaining your compost heap in a 20:1 ratio of carbon-to-nitrogen content.
Carbon-containing or 'brown' materials include sawdust, shredded paper, and dry leaves. A carbon-nitrogen ratio that is too high (35:1) will slow composting down. If it gets too low (around 20:1), you will start noticing foul odors emanating from your compost heap because of the excess nitrogen.
Materials That Should Be Kept Out of a Compost Heap
All organic matter will return to the earth at some point, but that doesn't mean you should add everything to your compost bin. Here's a quick list of what shouldn't go into your compost bin.
Weeds and diseased plants - A good compost heap will probably kill weeds and diseases, but why take chances? If you're keen to use as much of your garden waste as possible, you can pre-treat any weeds that may have gone to seed by sealing them in a plastic bag and leaving them in the hot sun for a few weeks before adding them to the compost.
Cooking Oils and Margarine - While they will break down eventually, these cooking products can take a long time and are best left out of your compost.
Fireplace Ash - Arizona soil is already very alkaline, and throwing in fireplace ash will make it even more so. Plants will struggle in earth that is too alkaline as it inhibits nutrient availability.
Maintaining a Compost Heap
To ensure rapid decomposition of your organic waste, grind it into small pieces before adding it to the pile. Doing this increases the surface area available to the organisms. When adding your green and brown materials, don't layer them, but mix them in well.
Keep an eye on the moisture content of your compost. It should feel like a damp, freshly squeezed sponge. In a desert environment, the main reason compost heaps take so long or completely stop composting is because of a lack of moisture.
Regularly turn the pile to aerate it and keep oxygen levels high. Sprinkle the heap with water as you turn to ensure an even distribution of moisture. The pile will heat up, ideally to around 130° F to 150° F. Let it sit for about seven days before turning again. If you want to monitor the temperature, you can purchase an internal compost thermometer.
The Best Containers for Arizona Compost
A compost bin isn't a complicated device. At a minimum, choose a bin that will keep birds, dogs, and cats out, but gives you easy access for turning and adding to the pile.
Many municipalities around Arizona are offering recycled trash containers to use as compost bins free of charge to residents. An optimal size for a compost heap is 3'x3'x'3 or 4'x'4'x'4'. You don't want a heap that is too small as the internal temperatures won't reach an optimal level. If it's too big, you will have trouble maintaining adequate moisture levels, and it will be cumbersome to turn and keep aerated.
A convenient location for a compost bin will be conveniently close to the kitchen. You will also want to make sure it's within easy reach of a hose for frequent watering. A shady area will also help you keep control of the composting environment.
How to Know When the Compost is Ready?
You will know your compost is ready to use in the garden because it will look markedly different from the materials that went into its creation. Ready to use compost will be a dark brown color and have a sweet earthy smell to it. While you are developing the compost, the process will be relatively slow. Once it has reached a sufficient size, let it age for at least 3-months to give the organisms a chance to finish the process.
Desert Composting Alternative
A popular composting method for Arizona gardeners is to use the compost as mulch for the garden. Because the compost is receiving moisture from the garden's frequent watering, you don't need to spend so much time monitoring the moisture levels.
When using compost as mulch, gardeners will start the decomposition in a bin as usual. Once the process is in full swing, the compost is then laid out as mulch. Leaves or straw are then added over the top of the compost to lock in the moisture and provide sufficient carbon content.
Composting isn't rocket science, so even when you get it wrong, you won't be able to ruin your compost; it will just dry out. A little experimentation with shade, carbon/nitrogen levels, and moisture will soon provide you with a never-ending supply of nutrient-rich humus to feed a thriving garden.
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