Infused With Life: How Microbes Work in Your Plant Growing System

Growing successfully with an organic system is impossible without the use of beneficial microbes. However, you cannot simply switch from synthetic to organic. Using beneficial microbes in a plant growing system requires a different set of growing parameters than are used in a totally synthetic system whether a hydroponics, soil-based or soilless environment. The switch requires a new approach that follows the rules of our natural world where plants have been growing successfully in the wild for millions of years.

In a synthetic system, plants are completely dependent on people to maintain feeding schedules and oversee delivery mechanisms. In a growing environment where microbes are used, people are no longer in complete control, and the plant is not completely dependent on people.

As people, we need to provide basic nutrients and microbes, but that is where our job ends in a microbe-growing environment. Now, the plant decides when it wants to eat, how much it wants to eat and how it prefers its food to be delivered—via roots, via leaves or a particular group of microbes. This enables your plants to grow bigger, faster and more nutrient-dense.

Why Growers Need Beneficial Microbes

Years ago, we didn’t need to add microbes if we were growing outside in soils since the microbes were naturally there. For many decades now, though, we have been killing off the naturally occurring microbes with salt-based synthetic fertilizers and toxic pesticides, fungicides, herbicides and even some organic pesticides. What we haven’t killed off directly has been zapped through pesticide drifts. The only way to get the beneficial microbes back into our plant growing systems is by adding them, as well as the foods that are needed to sustain those populations.

Part of our job is to be sure the salt levels in our growing system are below 100 ppm when we add microbes to soil or hydroponic systems. Microbes can still be added to leaves when using synthetic fertilizers on soil that are above 100 ppm, but not directly to the soil.

Microbes are like people in that they need food, air and water to thrive. If they are given too much salt they become dehydrated, shrivel up and die. If salt levels in your soil or nutrients are less than 100 ppm then you can add microbes (no matter if you are using synthetic or organic nutrients), but above that 100 ppm threshold, the microbes start dying off.

Why are microbes so necessary for successful growing when using organic nutrients? Let’s look to Mother Nature for the answer. The sun is the primary source of energy for all life on earth. Its energy is stored in bonds of carbon-based chemicals that are also called organic matter and are produced by plants through photosynthesis. This energy can later be released for use by microbes and by higher plants the process of respiration.

What does this mean for our plant growing systems? Organic nutrients are carbon-based, while synthetic nutrients are salt-based. Salt-based synthetic nutrients can diffuse directly into a plant through the cell walls, so microbes are not needed. Most carbon-based organic matter is chemically complex and cannot diffuse directly through the cell walls, so microbes are needed to consume that organic matter and break it down into plant available forms. Although there are some simple forms of organic matter that are not chemically complex and can convert to a form that is usable by plants, most organic nutrients are dependent on microbes for transformation.

In salt-based systems, the concentration of salts outside the root has to be extremely high in order to force the nutrients into the plant. When disease-causing organisms find their way into the system, they feed off these high nutrient concentrations and flourish, making salt-based systems extremely susceptible to disease. Natural systems are less susceptible, as long as the set of organisms in their soil is present.

Disease-causing organisms tend to have boom-and-bust life cycles. Once they’re established, they grow rapidly and damage everything; so, in order to prevent this, you need to ensure the habitat does not allow them to do so. High concentrations of nutrients provide the best conditions to allow these organisms to grow.

The chemical world has tried to sterilize their systems to prevent all living things from being there, but this is impossible. Instead of trying to kill everything, re-add the organisms that are beneficial to plants and prevent the disease-organisms from being able to get a foothold in the system.

If you are trying to grow in an organic system, you might be experiencing great difficulties and are unsure why. You are buying the best nutrients out there and applying them according to the instructions, but your plants are just not growing the same as they did when you were using synthetic nutrients.

You’ve added the bacillus subtillus and mycorrhizal fungi microbes—that means you have some of the puzzle right, but not entirely. You need to add a full spectrum diversity of beneficial bacteria, saprophytic fungi, protozoa and fungal and bacterial-feeding nematodes for complete nutrient cycling to occur. With only one species of bacteria and mycorrhizal fungi, you are missing thousands of other species of bacteria, saprophytic fungi, protozoa and nematodes.

Why do you need thousands of species and all those different groups of microbes? Again, let’s look to Mother Nature for the answer. Different microbes are activated under different environmental conditions—temperature, humidity and nutrient availability. If we have 20,000 to 40,000 different species of bacteria and 15,000 to 30,000 different species of fungi in one teaspoon of compost tea, some will be awake and some will be asleep.

Different types of plants need certain species of bacteria and since we have only been able to identify and culture less than 0.01% of the species of microbes out there in the world, we have to rely on the plant to pick and choose which microbes it needs to grow and thrive. A full spectrum of aerobic organisms is found only in products such as worm castings, compost and liquids derived from those materials, called compost tea.

Below is a summary of the basic nutrients and microbes necessary for growing in a natural system.

(Want to learn more about gardening and microbes, check out Getting To Know Your Microbes)

Compost Tea

Compost tea combines the benefits of compost with added foods (such as sea kelp and humic acid) to stimulate the growth of beneficial micro-organisms in the compost tea. Growing micro-organisms produce glues that instantly hold them onto leaf surfaces and fine soil particles. Compost tea is effective at covering all surfaces of a plant or soil with these beneficial microbes to provide: rapid protection against disease, nutrient cycling to transform food sources from sea kelp and humic acid into plant available forms soil structure, water retention due to air passageways created by the microbes in the soil and nutrient retention from sea kelp and humic acid.

Humic Acid

Humic acid is chemically complex, preventing the nutrients it contains to be used by plants. Beneficial, aerobic fungi usually consume humic acids and the fungi then hold nutrients that were contained in the humic acid. Bacteria can use the fungal waste products produced by the fungi, and fungi and bacteria need to be eaten by predators like protozoa or nematodes in order for the nutrients to be transformed into plant available forms. When fungi and bacteria are eaten, the nutrients that were once held within the humic acid are released in plant available nutrient forms.

Sea Kelp

Sea kelp contains some soluble nutrients that plants can use directly, but much of sea kelp is chemically complex. It is mainly used as a food by both bacteria and fungi, and when bacteria and fungi consume kelp, they retain the nutrients from the kelp in their biomass. The bacteria and fungi must then be eaten by either protozoa or bacterial and fungal feeding nematodes in order to transform those nutrients, originally from the kelp, into a plant available form.

Mycorrhizal Fungi

Mycorrhiza is a symbiotic association between a fungus and the roots of a vascular plant. Mycorrhizal fungi form critical relationships with most plants on the planet. Relationships are symbiotic when two or more different living organisms, such as mycorrhizal fungi and plants, form relationships. Mycorrhizal fungi and plants each receive mutual benefits from each other—the plant provides the fungi with sugar from photosynthesis and in exchange, the fungi gathers nutrients from rocks, sand, silt, clay and organic matter such as sea kelp and humic acid, then sends those nutrients back to the plant in exchange for more sugar.

Worm Castings

Worm castings contain a large variety of beneficial bacteria, fungi, protozoa and nematodes. These organisms colonize the soil rapidly and perform many different beneficial functions for plants, such as rapid protection against disease, nutrient cycling to transform food sources from sea kelp and humic acid into plant available forms soil structure, water retention due to air passageways created by the microbes in the soil and nutrient retention from sea kelp and humic acid.

(For more information on healthy mircobes, check out, Understanding the Benefits of Plant-based Nutrients and Healthy Microbes)