The following article first appeared in the Nevada County Grown 2019 Food and Farm Guide. It introduces the Sierrra Soil Biology Association, describes how plant-and-microbe communities work, and offers perspective on the current state of biological soil management. We hope it proves helpful.
By Wesley Sander
Owner/Operator, Foothill Biological Soil Health Services
When six of us first gathered for a potluck dinner in Auburn a little over a year ago, there was an undeniable spark.
All of us are, and probably always will be, geeky about soil biology. We love seeing healthy plants grow. We love collecting and assembling data. We peer through microscopes for hours on end. We found each other because we are all students, in one capacity or another, of the microbiologist and educator Dr. Elaine Ingham.
Ingham is the world’s foremost champion of a big-picture understanding of the soil microbiome, and of farming techniques that harness that knowledge to produce the healthiest plants possible, at any scale, while reducing costs. And that’s to say nothing of the possibilities for reversing climate change, as the world’s agriculture begins preserving carbon in its soils.
Among Ingham’s students worldwide, we are the largest localized gathering. We have since become the Sierra Soil Biology Association, a group of consultants and educators helping to promote an understanding of soil microorganism communities – of why they’re so important, and of ways that farmers, ranchers and gardeners can use this knowledge.
For some in our group, the journey began a few months before that first potluck. For others it was years. For Alane Weber, it started in the mid ’90s, when she began cooking small compost piles in her Bay Area backyard. The world was just beginning to perceive the importance of the microbial realm, that universe of creatures too small to see without a microscope, their vast web of relationships making soil health, and therefore plant health, function as nature intended.
Before long, Weber was teaching classes and training clients. Often she did the work herself, preparing microbe teas in a 250-gallon brewer and hauling a skid sprayer around in her pickup. The results were always remarkable. Plants grew vigorously, with no infestations or diseases.
Weber had worked since her teens in horticulture, including many years spent at one of the Bay Area’s largest nurseries. That experience had begun taking its toll. Years of routine chemical applications had left a toxic accumulation of metals in Weber’s body, creating a host of health problems. She had stopped working, hoping to detoxify.
That was when she heard about Dr. Ingham, then a professor at Oregon State University. Ingham had already begun turning away from academia, teaching independent courses around the country in a subject no one else seemed to know about: soil management based on an understanding of how microbes interact with one another, and with plants. The Soil Foodweb, Ingham called it. Weber soon stood out among Ingham’s students. A lasting friendship developed.
“Elaine was the one who put it all together,” Weber recalls. “What she was saying was just so different from everyone else.”
Ingham’s agricultural techniques stem from work she published with three colleagues at Colorado State University in the 1980s. The work demonstrated links between plant health and a basic pattern of development observed throughout nature. That pattern, called succession, involves the long progression of a natural area over time, from one kind of plant community to the next.
For any plant-and-microbe community, the first defining event is disturbance – fire, landslide, the plowing of a farm field. Microbial communities are largely destroyed, leaving only scattered survivors. Certain plants thrive in this chaotic environment, quickly setting seed and outcompeting what previously grew. Relatively few of these plants are of much use to us. We generally call them weeds.
Meanwhile below ground, the microbes that rebound most quickly from such a catastrophic event are bacteria, the smallest of single-celled creatures. As bacterial communities begin developing again, shorter grasses begin growing, feeding on the type of nitrogen made available by those bacteria. After many years, taller grasses may rise to dominance; then shrubs and vines, then trees. As the pattern progresses, fungal communities reestablish and proliferate underground until, eons later, dense groves of towering trees are found growing in soil that harbors many times more fungal biomass than bacterial.
Every plant is at home somewhere along this spectrum. Which means that, if we can adjust our soils’ biological balance while keeping the biomass of both groups at healthy levels, we can recreate the biological profile most favorable to our target plants. But that’s not all we need. To make the Soil Foodweb really work for us, we also need the rest of its denizens, and lots of them. Here’s the simplified rundown of how the system works, starting from the bottom:
On Earth, bacteria and fungi are the only life forms capable of digesting organic and mineral matter down to its constituent elements. Plants need these decomposers to supply the nutrients they need, but to make the transaction happen, they must offer something. So they inhale carbon dioxide from the air, exhale away the oxygen, and secrete the resulting carbon out into the soil, where bacteria and fungi feed on it.
Those bacteria and fungi can impart many nutrients and metabolic agents directly to their partner plants. But for plants to find all the nutrients they require, at the specific times they’re needed – for full nutrient cycling to occur – a soil must also contain predators and grazers. Single-celled protozoa (mostly flagellates and amoebae) feed on bacteria; nematodes (microscopic roundworms) and microarthropods (microscopic insects) eat fungi, bacteria and protozoa; earthworms and insects eat pretty much everything. The waste these organisms secrete contains the nutrients that plants require, in water-soluble form, ready for roots to absorb. If the system is healthy, plants feed themselves by offering the right carbon-rich compound at the right time, attracting particular decomposers that offer back specific nutrients.
So how do we harness this knowledge? We collect as many microbes as we can find, multiply them through proper composting, and reintroduce them to our soils. It is possible to build, in a matter of weeks, microbial density and diversity sufficient for a soil to naturally support vegetable crops, or grasses, or orchards, or vineyards. In the right environment, plants can achieve the health that allows their natural defenses to work against pests and diseases.
By developing the Soil Foodweb, therefore, we can practice agriculture free of the modern reliance on chemical nutrients and pesticides, and with significantly less water. In living soil, microbes hold moisture, transferring it from one individual to the next. Data assembled by Ingham and her students over the years has reliably shown decreases in water usage of around 50 percent in the first year of applying biology-based techniques.
“Trying to grow healthy plants using toxic chemicals seems to be such a contradiction that I always shake my head to fathom how we got here,” Dr. Ingham said recently. “We have to end the practice of using toxics to grow what we eat.”
For farmers, this all raises the question: where to get microbes? It’s a quandary often on the minds of SSBA’s founding members. Dr. Ingham has long addressed the challenge by training farmers to perform their own composting, usually sourcing ingredients on-site. But many growers aren’t prepared to undertake a new enterprise. Most conventional composters, meanwhile, face the prospect of learning new skills and overhauling their practices.
“The vast majority of commercial composters don’t know how, or are unwilling, to make biologically complete compost,” says Brian Vagg, who runs an Auburn-based consulting business with wife Shelby Vagg (both are SSBA founding members). “I have clients who need this kind of material.”