Dive Into the Rhizosphere: Soil Root Microbe Interactions

“Rhizosphere” isn’t really one of those words that gets thrown around a lot in casual conversation. And, while the idea of diving in for an evening of soil, root and microbe discussions might seem as intimidating, this evening’s talk was easy to follow and incredibly informative, led by Sunny Kaercher of Miller Soils and the guest speaker at Verde Natural’s fourth It’s Alive event. Kaercher has loved plants and plant systems ever since she was a child, and now she works with Miller Soils to help grows find balance and encourage beneficial biology in their systems. 

Even at the young age of 11 years old, Kaercher realized her love for plants. Early on, at her grandparents’ farm in Southern Idaho, she realized why. “Every summer my parents would ship me out [to the farm] for at least two weeks. It was a win-win for everyone; I grew up in a city, so I didn’t get to play in the mud really unless it was soccer practice or something. So, it was really fun to just kick it at the farm. My grandpa would turn on the hose at one end of the garden and there was a change in elevation, so the water would flow down. And I would spend hours maintaining and building my dams and culverts and canals and I was in heaven...I look back and think about these times and I’ve actually been really interested in system designs for a long time. My parents thought I might be a civil engineer. No, I like plants way too much.”

Kaercher’s fascination with and respect for systems, ranging from ecosystems to biological and microbial systems, is more than evident in both her passion and knowledge on the topics. And she cautions the crowd not to get too intimated, offering to walk them through some “basic science”, talk about how the rhizosphere works and the interactions that take place within it, as well as nutrition, soils and worms, and how to get the most out of your soils. Gauging the crowd, Kaercher begins by saying that this first part may take a few of them back to the days of high school biology and chemistry. For many of us in the audience, it was a much-needed refresher. 

“Really this talk is about relationships and flow, not so much soil."

Kaercher begins by breaking down the differences between ecology and biology and how each system interacts with each other to create and sustain balance. “Start with what plants need, where they get it from and how they get it,” she explains. Plants take in light with their leaves and convert to sugars that are used by the plant to draw water and nutrients from the soil using the roots. Plants share the same basic needs as humans–clean air, clean water, food and shelter (in the case of plants, shelter refers to general environment, not a roof)–and the rhizosphere is where the roots join or help create soil food webs. In the same way that humans take in oxygen and expel carbon dioxide, plants take in carbon dioxide and release oxygen and a variety of byproduct molecules. 

In order to foster the best culture, you need to focus on your soil composition, its mineral content, as well as the particle size of the minerals used. Clay is 100x smaller than sand, but sand has very little nutrient or water retention. A mix of all soil types can be best, but you generally want 5-15% organic matter in your soil. “If you can pick up your soil in your fist and make a ball and it sticks but when you drop it, it crumbles, you’re probably safe…Color is also a great indicator; darker soil has more organic material and nutrients.”  

How the Rhizosphere Works: “I like to think of it as the 'shakedown street' of the plant world because it is where all the goodies are exchanged”

In a nutshell, it works like this: Roots produce sugars, which are then eaten by the bacteria and fungi who retain the nutrients. Then, protozoa and nematodes eat the bacteria and fungi, releasing those nutrients back into the soil to be absorbed by the roots, turned back into sugars, and cycle continues. Much of this depends on the soil’s ability to retain nutrients, as discussed, as well as how well it is aerated, something that the biology of the system often helps sustain. As worms move through the different soil layers, and as forces and weight from above compact soils, different bacteria and organic matter is moved throughout the web. The web of bacteria, nutrients and biotics also works as a communication network between plants, warning of droughts or other conditions that may be moving between them.

9 Actions You Can Take to Let Living Soil Thrive

  1. Oxygen: getting dissolved oxygen into your grow system is great, especially if feeding with in-water nutrient solutions. Make sure your oxygen is at least 6PPM or higher.

  2. For compost teas and extracts: make sure oxygen is in there. Make sure you’re using quality compost source; if compost is bad, it multiplies in your plants.

  3. Commercial biology: This shouldn’t be your first choice but there are good products that can be used in small doses.

  4. Make sure to feed the soil not the plants. Feed microbes as they process everything for plants.

  5. Build your soil with quality ingredients. Especially if using no till or reusing soils, you want something that will last.

  6. Ask questions; It will get you were you want to be.

    1. What does my plant need?

    2. Where is it coming from?

    3. How is it getting it?

    4. Where is it going?

  7. Pay attention to your potting soil.

    1. Almost anything in a bag has no mineral content in there; no soil.

    2. Bags of soil often replace mineral with other substrates like cocoa core or peat.

    3. Look for organic certifications

    4. Look for cannabis-specific organic certifications

    5. Look at compost source. Ask about the compost source and how old it is, where it came from. Larger companies that have scaled up have lost access to good compost which can be where you start to get bugs and problems.

    6. Ask for an analysis. If you don’t own a microscope and know how to use it, send your soils in to labs that will test them for you.

  8. Introduce and maintain Biology: Biology impacts the entire system and helps to maintain aeration and organic matter.

  9. Knowledge is power; Track Your Data. Grow logs are an excellent way to understand how your plants and soil are interacting with each other.

If any of this piqued your interest in growing and modifying your soils, Sunny Kaercher’s talk is packed with information that you do not want to miss out on. Visit this page for more of Kaercher’s presentation at the fourth It's Alive talk as well as recaps from previous Verde Natural events. 

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Ben Owens

Ben Owens began his cannabis career during his undergraduate years at the University of Missouri – Columbia with the help of a few friends, a blunt wrap, and a gram of ganja. Graduating with a Masters and Bachelor’s in Strategic Communication & Journalism, Owens’ focus has been on integrating the professionalism and high standards of the advertising and journalism industries into the cannabis and counter culture realm. Owens founded CannaVenture® in March 2016 as the merger between two of his utmost passions: the outdoors and cannabis.