Understanding the Soil Food Web
February 16th, 2015
By Ananda Fitzsimmons
As I mentioned in my last post, I attended a three-day workshop with Dr. Elaine Ingham in Montreal in January. Dr. Ingham wrote the first monograph on The Soil Food Web back in 1986, along with her husband, who is also called Dr. Ingham. Since then, she has made it her life’s work to study and understand the interactions that make up the life of the soil and has popularized the concept of the Soil Food Web, making it very accessible to non-scientists.
Fertile soil is alive with bacteria, fungus, protozoan, nematodes, microarthropods, all the way up to the critters we can see with the naked eye. Many agricultural soils have had their biological population decimated through over-till and the use of synthetic fertilizers, pesticides and fungicides. According to Dr. Ingham, if we can restore the full balance of players in the Soil Food Web, we would have little need to use these amendments to grow healthy nutritious plants. The mineral matter is there in the earth, we are just lacking the biology to make it available to plants.
In general, agricultural soils have way more bacteria than fungi, as fungi are more vulnerable to tilling. Tillage breaks up the web of mycelium that forms the root system of fungi. Without that population of beneficial fungi, the fungal pathogens have a heyday, and when we start using fungicides, it just makes the problem worse. Getting the right balance between fungus and bacteria is key to healthy soil. Different crops require different ratios of fungus to bacteria.
The bacteria and fungus solubilize and sequester nutrients, and they colonize on and around the roots of plants. It is the beneficial protozoa and nematodes that release those nutrients when they prey on the bacteria and fungus. This keeps the nutrients from being washed away into the waterways and provides a time-released delivery to the plant roots.
Dr. Ingham recommends inoculating the soil with compost or compost tea to re-establish the full diversity of soil biology. Of course, it is critical to get the balance right when making compost. Otherwise, it won’t do the job. Many composts are not up to standard, especially those made in municipal composting facilities, which, as Dr. Ingham says, ‘’ …that isn’t compost; it is reduced waste material!’’ She proposes that we all buy microscopes and examine our soil, compost and compost tea to make sure we have enough bacteria, fungi, protozoa and nematodes in every gram.
Next time, I will tell you about using compost tea along with our Garden Solution, which is, as far as I’m concerned, is a marriage made in heaven!