Did you know that one teaspoon of top-notch garden soil can hold a billion bacteria, beneficial fungi, protozoa, and nematodes? You might be asking yourself, “What are protozoa?” Or exclaiming, “I thought nematodes are bad for your garden!” The key to growing plants successfully is to build, feed, and sustain the soil microbiology in your garden, thus creating a soil food web.
In order to do this, we must first understand what goes into a healthy and vibrant soil. The science of soil biology can be intimidating. But by covering the basics and keeping it simple, everyone can learn how to grow healthy and delicious plants in our desert environment.
A soil food web is a community of living organisms in soil. In that community live bacteria, fungi, nematodes, protozoa, earthworms, arthropods, and the roots of living plants. These are the workhorses of your garden. These living organisms break down the compost and soil amendments we add to our gardens. A lack of healthy organisms means that any nutrients present in the soil will not be available in a water-soluble form for plant roots to uptake. So it’s not just about adding organic amendments. You need to add living organisms and create conditions for them to thrive in your garden. If your garden soil is lacking any one of these major living organisms, your plants are going to exhibit signs of stress and attract garden pests.
Growing our own food and medicine is a labor of love that requires us to set our own roots down into the earth. This means that, along with nurturing our own connection with nature, we must also be open to the lessons our land and soil are teaching us. I didn’t fully understand the importance of microbes until my garden started to struggle and produce unhealthy plants. Every season I added fresh compost to my garden. Every season some plants would succumb to the weirdest and seemingly random diseases and bugs. As I interacted with my little piece of land, I soon came to see and experience the web of life that was crucial to sustaining healthy conditions. The specific plant diseases and bugs destroying my plants also pointed to a pattern: healthy soil life and fertility are critical for a healthy garden.
Just as in the human body, plants need the right nutrients to communicate health and wellness. Plant nutrients are classified into two groups: macro and micro. The macronutrients, what plants need more of, are: nitrogen, potassium, phosphorus, calcium, sulfur, and magnesium. The micro, what plants need in small amounts, are: boron, copper, iron, manganese, molybdenum, and zinc. Plants use their roots to take up these nutrients via water. This is why soil pH matters—pH is a logarithmic scale ranging from 0 to 14, where 7 is neutral. The pH stands for the “potential to be” a hydrogen ion. The hydrogen ions in the soil actually determine the alkalinity or acidity of soil.
In the rocky foothills of the Tucson Mountains where I garden, the soil is alkaline (low in hydrogen ions) and annual vegetables and fruits prefer a slightly acidic soil. For plants to have access to the water-soluble nutrients in the soil, we need to have the right pH. This is why gardeners in Baja Arizona dig their garden beds two feet down, amending with 50 percent native soil and 50 percent compost. We need to inoculate our soil with quality organic matter, preferably rich in microbes, to create conditions that our plants can thrive in.
So what can you do to fortify and help establish a healthy soil food web in your garden? You can start a worm bin and make a compost tea brewer. Worms are a key organism in the soil food web because they convert biomass into a plant-soluble form by creating worm castings and aerating the soil in the process. Their manure is full of beneficial microbes, growth enzymes, humus, and so much more. Compost tea is made by aerating high-quality worm castings for 24 hours or more to extract and multiply the microbes in the castings into the billions. Compost tea yields the most value from “worm work” (theirs and ours). A monthly soil drench of your garden soil with aerated compost tea, using high quality worm castings, will jump-start the soil food web.
We are all busy. As a parent, I want to work smarter, not harder. Saving time, money, and physical labor are also important factors that influence how we interact with our gardens. Another benefit of “worm work” is the biorecycling of food waste that may otherwise unnecessarily end up in a landfill. Save your time, money, and lower back all while decreasing your carbon footprint (another reason I love worms). Once you have a successful worm bin, you can use worm castings (i.e. worm manure) to build your soil. Building and maintaining a worm bin is also a great hands-on lesson for children. It is an excellent minilab that integrates environmental science with fun, and is perfect for small spaces and classrooms. In my house, both of our elementary-age children built their own bins and now maintain and harvest from them.
Worms need shade, water, and food to do well in our hot summers. They don’t like very cold weather either, so it’s important to place them in a good microclimate in your yard. Generally speaking, worm bins kept outside are made out of wood, so they breathe better, and they are relatively cheap to build. The best set-up for an outside worm bin is under a shady mesquite tree. Storage totes and five-gallon buckets are very popular as well, but they tend to heat up outside because they aren’t as breathable. I like placing indoor worm bins in the laundry room, under kitchen sink cabinets, or in closets.
Go to my YouTube channel, The Sonoran Desert Grower, to find a step-by-step video for building an affordable worm bin and compost tea brewer. In the next issue of Edible Baja Arizona, I will walk you through how to build a worm bin, showcasing both super affordable and more professional models.
Stay tuned! ✜
Zotero Citlalcoatl is a permaculture designer and herbalist of the Sonoran desert. Follow him on Instagram at @the_sonoran_desert_grower.
How to Make Compost Tea
You’ll need four to six cups of worm castings (EcoGro sells quality worm castings), four gallons of dechlorinated water, six tablespoons of organic, unsulphured molasses, and a home-scale compost tea brewer.
A home-scale compost tea brewer set-up consists of an air pump, air tubing, an aquarium air stone, a five-gallon paint strainer bag, and a five-gallon bucket with a lid. To make compost tea, place the worm castings into the five-gallon paint strainer bag, tie it with a knot, and place into the five-gallon bucket. Inside the bucket, place the airstone with up to four gallons of dechlorinated water. Connect the air tubing from the air pump to the air stone inside the five-gallon bucket, aerating it for the brew process. You want an aquarium air stone that produces big bubbles instead of small bubbles; bigger bubbles won’t damage the protozoa and fungi in the tea. Typically compost tea is brewed for a 24- to 36-hour period. If you own a microscope, you can see the microbial activity in your tea, and identify some of the main players of the soil food web. Some gardeners use a microscope to dial in the brew time, so they’re using their tea when it’s the most microbially active. It’s important to use compost tea within six hours after turning off the air pump. The most it can be stretched out is for an additional 48 hours, by keeping it aerated, and adding more molasses to feed the microbes in the brew. Just remember that fresh tea is always the best for your plants, but extending the brew time is an option.