Healthy Soil — Healthy People
Bacteria are tiny one-celled organisms generally 4/100,000 of an inch wide (.00004). A teaspoon of productive
soil generally contains between 100 million and 1 billion bacteria. That is as much mass as two cows per acre.
A ton of microscopic bacteria may be active in each acre. While bacteria may be small, they make up both the
largest number and biomass (weight) of any soil microorganism.
Bacteria are similar in size to clay soil particles (<.2 µm) and silt soil particles (2-50 µm). They grow and live in
thin water films around soil particles and near roots in an area called the rhizosphere.
Bacteria’s small size enables them to grow and adapt more rapidly to changing environmental conditions
than larger, more complex microorganisms like fungi.
Most soils are simply a graveyard for dead bacteria cells. Bacteria are so simple in structure that they have
often been called a bag of enzymes and/or soluble bags of fertilizer. Since bacteria often live under starvation
conditions or soil water stress, they reproduce quickly when optimal water, food, and environmental conditions
occur. Bacteria population may easily double in 15-30 minutes. Flourishing microbial populations increase soil
productivity and crop yields over time.
Just as we have unwittingly destroyed vital microbes in the human gut through overuse of antibiotics and
highly processed foods, we have recklessly devastated soil microbiota essential to plant health through
overuse of certain chemical fertilizers, fungicides, herbicides, pesticides, failure to add sufficient organic
matter (upon which they feed), and heavy tillage.
These soil microorganisms, particularly bacteria and fungi,
cycle nutrients and water to plants, to our crops, the source of our food, and ultimately our health. Soil
bacteria and fungi serve as the "stomachs" of plants. They form symbiotic relationships with plant roots and "digest"
nutrients, providing nitrogen, phosphorus, and many other nutrients in a form that plant cells can assimilate.
Reintroducing the right bacteria and fungi to facilitate the dark fermentation process in depleted and sterile soils is
analogous to eating yogurt (or taking probiotic drugs) to restore the right microbiota deep in your digestive
We used to think that soil organic matter was formed from leftover bits of plants that were difficult to degrade.
Over time, we thought that these plant particles became chemically transformed into what was called humus,
dark, long-lasting material left over when dead plants and animals decay. This view suggested that the key to
building soils was getting a lot of dead plant material into the ground.
Recent technological advances have transformed our understanding of soil formation. There is now strong
evidence that that the most persistent forms of soil carbon are formed primarily from dead microbial bodies
rather than from leftover plant parts. The vast majority of old soil carbon appears to have undergone
microbial decomposition. While plants are the original source of carbon for soils, microbes control its fate by
using it as food, thus ensuring that at least some of it will remain in the soil.
To maximize the proportion of plant carbon that is transformed into soil organic matter, we should aim to
support and enhance soil microbiomes that quickly and efficiently transform dead plant materials into soil
organic matter. Healthy soils should also contain microbiomes that help prevent disease, cycle nutrients and
help reduce plant stress.
Much recent research has focused on adding organic material back to soils to restore them. This is an
important strategy, but I believe we also should aim to enhance the microbes that are responsible for soil
Legume plants like beans, peas, clover, and locust trees partner with soil bacteria called rhizobia to
extract nitrogen from the atmosphere
Retain nutrients in the soil, preventing them from leaching
Compete with, inhibit and consume diseases
Decompose plant residue, toxic materials and pollutants that kill plant roots
Form soil aggregates that improve water infiltration, root penetration and water-holding capacity of the soil
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