The Organic System – Soil Bacteria

The Organic System – Soil Bacteria

The Organic System – Soil Bacteria

In the Organic System, soil bacteria are key roleplayers in the soil food web that supports our plants and the health of the soil.  We, as gardeners, tend to think more about the parts of our garden above ground.  In reality, we should be thinking just as much about the parts of our garden below ground.  We are, in effect, ranchers of an amazing array of life forms that are an integral part of the whole garden ecosystem.

What are bacteria

Most of you remember enough of your high school biology to know that bacteria are single-celled organisms that are typically cylindrical shaped and microscopic.  Though they are tiny, they make up for size in numbers.  In healthy soil, a teaspoon of soil usually contains between 100 million and 1 billion bacteria.

An acre of well-managed soil can contain a ton of bacteria. Bacteria are more prevalent than any other form of life on the planet.  They exist everywhere.  There are more bacteria in and on your body than there are living human cells by a factor of 10 to 1.  Up to 3 percent of your body weight is made up of bacteria. 

Types of Bacteria

The Organic System – Soil Bacteria

Bacteria fall into four functional categories.  The most important to gardeners are those in the decomposer group.  These bacteria consume simple carbon compounds and leave behind the materials that feed and support the rest of the organisms in the soil food web.  Many of these decomposers immobilize certain compounds within their cells, preventing the loss of these nutrients from the root zone.

The mutualists specialize in partnering with plants.  These specialists include nitrogen-fixing bacteria.  The third group of bacteria is lithotrophs.  Lithotrophs obtain their energy from compounds of nitrogen, sulfur, iron, or hydrogen instead of carbon.  Their ability to manage a wide range of other materials is important to the delivery of micro-nutrients to plants in useable forms. The last group of bacteria is pathogens.  Pathogens are those that we usually associate with disease or problems with our plants and sometimes with ourselves.

What do Bacteria Do?

The Organic System – Soil Bacteria

Bacteria perform so many functions within the soil that it is almost impossible to detail the entire catalog of functions.  These small organisms are at the core of water dynamics, nutrient cycling, and disease suppression. Bacteria produce most of the substances that bind to soil particles to create aggregates.  Aggregates help improve water infiltration, soil stability, and provide spaces for many other organisms to set up shop.  A diverse and healthy bacteria culture in the soil will suppress many diseases causing organisms below and above the soil.

The More Important Players.

A diverse and broad spectrum of bacteria is important to soil health.  There are a few about which we, as gardeners, should be concerned.

Nitrogen-fixing bacteria

This group of bacteria forms symbiotic relationships with plants at the root level.  The most common of these are legumes.  The nitrogen-fixing bacteria create their workspaces in nodules attached to the roots of plants.  Carbon is provided by the plant and the bacteria convert nitrogen into a compound that can be used by the plant.  Leaves and roots from these plants, when left in the ground, return this nitrogen to the surrounding area.

Nitrifying Bacteria

Nitrifying bacteria convert ammonia compounds to nitrates (NO3), the form most preferred by plants.  While this is important for plants, it creates problems in gardens or fields under cultivation because nitrates are highly mobile and leach from the soil more easily than other forms of nitrogen.  In some un-altered soils, such as undisturbed forests, natural processes inhibit the nitrifying process.


The Organic System – Soil Bacteria

Actinomycetes are a huge group of bacteria that exist in the soil.  These bacteria grow together like the hyphae associated with fungi.  It is this group of bacteria that give our soil the earthy smell that we enjoy from freshly turned earth.  Actinomycetes are decomposers and are important in breaking down hard to decompose compounds such as cellulose.

Location, Location, Location

Where do bacteria reside?  Everywhere is the answer to that question in a broad sense.  However, different soil bacteria favor different conditions.  On the whole, bacteria exist in the rhizosphere, that small region adjacent to and around the plant roots. Different bacteria may be present at different times depending on the condition of the soil, the food matter that is present, and the needs of the plants themselves. 

Promoting Bacterial Diversity.

It is important to adopt gardening strategies that encourage a diverse bacterial culture.  Many of these practices are part of the basic Organic System that we promote.

Don’t Till

Tilling destroys the structures that bacteria and fungi create in the soil leading to a breakdown of the soil structure, erosion, compaction, and a loss os habitat for the bacteria and fungi.

Don’t Use Synthetic Pesticides, Herbicides, and Fertilizers

If we are trying to grow a rich and diverse bacterial and fungal soil network, why would we want to put anything on or in the soil that would kill these organisms?  If these products kill the bugs and plants above ground, it stands to reason they will do the same for the organisms that exist below ground.  Even salt-based synthetic fertilizers damage the soil biome in many ways.


The Organic System – Soil Bacteria

Mulching helps protect the soil.  Much of the living activity within the soil exists in the top few inches of soil, and it is this area that is most vulnerable to damage by the sun and other weather factors.  Mulching helps protect the soil biome from damage caused by UV rays and extremes in heat and cold.  Mulching will also mitigate the loss of valuable soil moisture through evaporation.  Applying good mulch means a continuing supply of organic material is always available for the bacteria and fungi, creating a richer and more diverse habitat.

Keeping your underground livestock happy and healthy is just as important as caring for your plants.  In the end, it is this vast universe of unseen creatures that provides for good soil health.  Healthy soil, rich in bacterial life, is the key to healthy nutrient-dense plants in your garden.  Feeding the soil is the key.

Links and Resources

For more information about organic gardening, lifestyles, and living, visit our website at West Texas Organic Gardening.

If you found the information here helpful, you might also find these articles on our website of interest.

Organic Growing Myths

Toss Your Tiller


If you have more specific questions or problems, you can contact us using the contact form on our website. You can also post your question to our community forum at this page; West Texas Organic Gardening Community Forum.

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