A battle for your garden, invisible to the naked eye, is raging in your root zone. Trillions of microscopic critters are viciously competing for dominance. What are they? What do they do? And why does it matter?
You may have heard that a hospital is the best place to get sick – even though everything is ultra-sterile. When good microbes are gone, bad ones move in. Our world functions best in partnership with good microbes to protect us against invisible threats and to perform functions impossible for the grower. Nature’s way is to support and partner with the beneficial microbe community. Successful growers know that healthy microbes are the key to increasing quality, and yield while minimizing plant stress. Healthy soils contain a mix of various microbes that can be either beneficial or harmful to your plants. We can separate these organisms into four primary microbes in soil; protozoa, nematodes, bacteria, and fungi. Protozoa and nematodes are larger organisms that perform specific and important functions in healthy soil, such as eating bacteria and fungi, as well as protecting the rhizosphere (area directly around the roots). Most terminal crops, however, don’t make full use of these creatures since the cycles are short and often soil isn’t reused. More important in these applications are bacteria and fungi. For the purpose of this article, we’ll focus on these, since they are the base of the soil food web.
Bacteria are the smallest of microbes. They tend to be the most diverse and resilient too. Bacteria are the first to establish populations in a soil environment. In fact, they require little time and resources to begin functioning. These microscopic creatures are the workhorses of the soil, tuned to perform specific functions. Bacteria don’t eat like we do. Instead, they simply absorb small molecules through their cell wall(s). Since most compounds in soil are larger “poly” molecules, bacteria produce enzymes and send them out to cut up large chunks into smaller absorbable molecules. Bacteria like to eat simple sugars as their primary food source. They are able to consume small sugar molecules quickly without enzymatic digestion. They can break down large sugars with enzymes but it takes some time. These are some of the functions bacteria perform:
- Produce hormones, vitamins, and other bio-stimulants
- Convert nutrients into forms that plants can use
- Create a sticky slime that helps bind together soil particles and improve soil structure
- Protect the rhizosphere (area immediately around the roots) from invading bad pathogens and organisms
- Release stored nitrogen as nitrates
- Some bacteria effectively pull gaseous nitrogen from the air and fix it into a form plants can use
One of the most important factors in maintaining a healthy bacterial population is plenty of carbon in the soil. Carbon acts as an anchor for bacteria, something they can hold on to. Without a solid platform, bacteria are easily washed away from the root area. Carbon can be introduced to soil with activated charcoal, organic acids (L-amino acid, Humic acid, etc.) or other organic matter.
Most growers know of Mycorrhizal fungi. This term actually refers to the symbiotic relationship that certain fungal strains develop with plants. (Myco refers to fungi, whereas rhizal refers to the rhizosphere, root system). This relationship is complex and diverse. Basically, the fungi attach to the plant’s roots. The plant exudes sugars, which feed and stimulate the fungi. In turn, the fungi convert and transport nutrients and stimulants into the root tissue. Most types of Mycorrhizal fungi take several weeks to fully establish a colony on the roots and start performing their functions. Because of this, fungi tend to perform better in environments where plants exist for longer periods and soil remains undisturbed (forests, perennials, shrubs, etc.). Fungi are not as good at breaking down and consuming simple sugars, as are bacteria. Fungi tend to perform better with larger complex food sources. They are, however, able to consume small sugar molecules quickly without enzymatic digestion. They can break down larger sugars with enzymes too, but it takes some time. These are some of the functions fungi perform:
- Build networks of ‘hyphae’ – strands that help transport nutrients across distances to the rhizosphere
- Pull nutrients directly into the root hair
- Build a protective layer around root hairs
- Increase root surface area, which can enhance moisture and nutrient uptake (especially phosphorus)
- Break down complex organic matter into usable compounds
- Protect roots against bad pathogens and pests
- Some fungi grow inside plant tissue and protect against systemic attacks, like powdery mildew
- Release stored nitrogen as ammonium