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Soil Biology

I recently was part of a symposium on soil conservation.  I spoke about the benefits of soil biology, how to improve soil biology and how it related to soil conservation and sustainable practices.  This is always a difficult subject to communicate especially with the embedded ideas of growing using chemicals.  I have tried to simplify the message by explaining that soil biology uses living organisms to create the same type of environment for roots that injecting chemicals would.  I am always open to other ways of explaining it but basically I try to use the example of probiotics and preventative care versus treating symptoms.

A more detailed explanation I went through in my presentation was explaining the soil food web (which many growers are familiar with) and discussing some of the elements of it.

Different explanations seem to resonate with different growers.  Basically, the soil food web exists to break down organic matter to create nutrients for plants.  The life in soil then converts them to food.  In this manner, plants become stronger working for themselves rather than relying on chemical injections to feed the roots.  Some important members of the soil ecosystem:

Beneficial Bacteria

- Rhizobacteria: form a symbiotic relationship with plant by converting nitrogen (from air) into a nutrient for the plant once embedded in root system

Actinobacteria: Critical for decomposition of organic matter and humus formation

- Bacillus: Protect roots and aid in nutrient uptake


Through bioturbation, disturbance of the soil, earthworms create passages ways for air and water.  In addition, worm castings are a source of nutrients that roots can feed off of, creating NPK with soil.  As we have mentioned before in the newsletters, earthworms are an easily observable sign of healthy soil

Beneficial Nematodes:

These are microscopic organisms which look like worms.  Predatory nematodes kill pests (borers, cutworms, grubs, etc.) and protect roots.


These are single cell organisms that eat bacteria which then releases nitrogen (in form of ammonium).  This also regulates bacteria populations


Anthropods are essentially bugs (Centipedes, spiders, etc.).  These are very important for nutrient release in the soil.  They shred organic matter, mineralize nutrients, and control pests.

Enhancing Soil Biology

There are a number of methods to enhance soil biology and foster a beneficial ecosystem at the roots.  These include:

  • No Till/Limited Till: This involves growing without disturbing the biology through tillage.  Tillage should be done infrequently.  This will add organic matter and reduces erosion as well as build up colonies of beneficial organisms.
  • Cover Crop: “Green Manure” increases nutrients in soil and increases organic matter when it is plowed under.  Many non-organic growers find it can produce the same results as concentrated forms of nitrogen.  It also enhance soil structure and creates less erosion.  Another reason growers use cover crops is for disease and pest management.  It can introduce predators or draw away pests in addition to being a weed control when rolled down.
  • Crop Rotation: This has been a long standing means of decrease pests and pathogens.  It also helps build nutrients and soil biology and reduce erosion.
  • Increasing Organic Matter: Adding compost/mulch or other soil amendments gradually increases the organic matter in a soil.  This is broken down into humus for fertilization and soil biology.  It provides minerals and nutrients and also reduces erosion.

We are currently embarking on an ambitious project converting 60 acres to certified organic crops.  As part of the project we will be optimizing organic inputs and testing methodologies side by side.  The goal is to show reduced costs with similar yields to current conventional practices.

Good Growing,
Graham Phillips

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