By Colin Bell, PHD And Matthew Wallenstein, PHD

All growers know that plants need light, nutrients, and water to grow. But recent scientific advancements have revealed how soil microbes can take plant growth and health to the next level. It is increasingly clear that plants need beneficial microbes to maximize their phenotypic potential. Many growers are discovering the benefits of integrating microbial inoculants into their indoor and outdoor cultivation management practices.

Microbes are the basis for all life on Earth. Bacteria and fungi shaped our planet to create the very foundation upon which plants exist––from the carbon dioxide they breathe to the soils they grow in. About 700 million years ago, plants evolved into a rich microbial world. Their roots extended into soils already teeming with microbial life. Ancient plants quickly evolved to actively support their microbiome by releasing sugars and other metabolites through their roots, which microbes eagerly use for food. In return, soil microbes break down dead plant material and recycle nutrients. In nature, all plants are surrounded by diverse communities of bacteria and fungi––different forms of microbes that we collectively call “the microbiome.”

In natural soils and well-nurtured agricultural fields, microbes are abundant and omnipresent. In a handful of healthy soil, there are billions of individual microbial cells. These cells represent tens of thousands of different bacterial and fungal species. Thousands of scientific publications have revealed the many ways in which soil microbes support plant growth. For example, by making nutrients more available for plant uptake, they maximize root growth, flowering, and bud production. Microbes also communicate with plants through chemical signaling, helping plants respond to environmental stresses and thus preventing nutrient lock-out events. A healthy microbiome can trigger a plant’s immune system to fight diseases and also create a barrier that inhibits pathogens.

In nature, plants are able to select particular microbes from the tens of thousands of species living near their roots in order to maximize their success. They engineer their microbiome through the chemistry and quantity of chemicals they release from their roots and through the timing and rate of nutrient uptake. However, managed agricultural and horticultural systems have much lower microbial diversity for the plants to choose from. As a result, plants are unable to optimize their microbiome without the deliberate addition of microbial inoculants.

Beneficial microbes are the key to unlocking the potential of the plant’s genetics to maximize yield and bring out each strain’s unique qualities. When deciding to use microbes in your cultivation practices, a good place to start is by trying to mimic key features of natural systems, where plants and microbes work together in harmony. In nature, no microbe lives alone. Instead, microbes inter- act closely with each other, working in groups to perform complex functions like breaking down plant material to release nutrients. Each microbe completes a different step in the process and then performs a metabolic hand-off. This is analogous to assembly line workers that specialize in specific parts of a complex process. A healthy microbiome should contain groups of microbes (known as consortia) that work together to conduct critical functions.

Whether you grow hydroponically or in soil, indoors or outdoors, you can put the power of microbes to work. There are many ways to enhance your microbiome. Some growers produce their own compost tea––an inexpensive way to add living microbes to your system. There are also many commercially available microbial formulations that include one or more species of bacteria or fungi. Beneficial bacteria are most often inoculated into soils or hydroponic systems to promote plant growth by increasing plant nutrient uptake. One way bacteria accomplish this is by releasing enzymes into the soil or other growth media. Enzymes catalyze the breakdown of nutrient-rich molecules into plant-available forms. Soil bacteria can produce many different types of enzymes to cycle import- ant macronutrients like nitrogen and phosphorus for plant uptake.

The incredible diversity of the microbial world was unknown prior to advancements in genomic techniques that have been made in the last few decades. We are now in the midst of a microbial revolution. Plants and microbes have been closely intertwined throughout evolutionary history. New microbial technologies and management practices are making it easier than ever for cannabis growers to harness the power of natural soil microbes and grow the most productive and healthy plants possible.