The Soil Food Web

“There can be no life without soil and no soil without life: they have evolved together.”

-Charles Kellogg

“Soil without biology is simply geology - the study of rocks.”

-Ray Archuleta

Soil Food Web

Soil is a living system

Soil micro-biologists have concluded that roughly 95% of the functions we expect the soil to perform are biologically driven.

Ignoring this biological or natural system mother nature has put in place is why we are now so dependent on fertilizer, fungicide, insecticide & are now experiencing problems such as salinity, compaction, poor water infiltration, disease, insect pressure, etc.

Livestock

Biomass below ground?

Care for your below ground livestock, like you would your above ground livestock.

1. Feed them a steady flow of carbon via a living root

2. Provide a balanced C:N Ratio

Note: 27,000 Ibs/acre of below ground biomass, the weight of approximately 18 cows.

If we shut off this liquid carbon pathway (food) what will the below ground livestock eat?

1. Plants feed carbon (food) to bacteria & fungi that was produced by photosynthesis.

2. Consider phosphorus solubilizing bacteria as an example. Once fed, it can perform it’s evolutionary task of solubilizing unavailable phosphorus for the plant. This phosphorus is now considered to be in an organic form of P and plant unavailable. This is known as immobilization.

3.Since that phosphorus is in the organic form & plant unavailable, Mother Nature needed to figure something out - so she introduced the protozoa, nematodes & arthropods. (3rd trophic level)

4.When this trophic level consumes the phosphorus solubilizing bacteria, it is released as an inorganic form and plant available. This process is known as mineralization.

The Bacteria

The decomposers of simple carbon chains. (Low C:N ratio residue & root exudates)

The mutualists form symbiotic relationships with the plant. The most common mutualists most folks are familiar with are rhizobium bacteria or “nitrogen-fixing” bacteria.

Actinomycetes are a large group of bacteria that grow as hyphae like fungi. They are responsible for the “earthy” smell of healthy soil.

The fungi

Saprophytic Fungi primary decomposer of complex carbon chains (dead plants) Bacteria can then decompose the simple chains. We recognize this fungi as the white filaments breaking down residue that are visible to the naked eye.

Mycorrhizal Fungi create a symbiotic relationship with the plant. To learn more about the formation & importance of mycorrhizal fungi, click here. Mycorrhizal fungi are not visible to the naked eye.

The Predators

Protozoa

as mentioned earlier, these guys will consume the bacteria and fungi & excrete the excess nutrient in plant available form.

Source: Elaine Ingham. Soil Protozoa. NRCS Soils

The Predators

Nematodes

as mentioned earlier, these guys will consume the bacteria and fungi & excrete the excess nutrient in plant available form.

There are generally 4 classifications of nematodes and their roles in our soil:

1. Eat Bacteria

2. Eat Fungi

3. Eat Each Other

4. Root Feeders (bad guys that thrive in anaerobic soil conditions)

Source: Elaine Ingham. Soil Nematodes. NRCS Soils

The Predators

Arthropods

Shredders help bacteria digest residue

Source: Andrew R. Moldenke. Oregon State University

Ecosystem Engineers

The earthworms

Earthworms dramatically alter soil structure, water movement, nutrient dynamics, and plant growth.

Stimulate microbial activity. Although earthworms derive their nutrition from microorganisms, many more microorganisms are present in their feces or casts than in the organic matter that they consume. Increased microbial activity facilitates the cycling of nutrients from organic matter and their conversion into forms readily taken up by plants.

Mix and aggregate soil. As they consume organic matter and mineral particles, earthworms excrete wastes in the form of casts, a type of soil aggregate.

Increase infiltration. Earthworms enhance porosity as they move through the soil. These burrows can persist long after the earthworm has died, and can be a major conduit for soil drainage, particularly under heavy rainfall.

Improve water-holding capacity. By fragmenting organic matter, and increasing soil porosity and aggregation, earthworms can significantly increase the water-holding capacity of soils.

Provide channels for root growth. The channels made by deep-burrowing earthworms are lined with readily available nutrients and make it easier for roots to penetrate deep into the soil.

Bury and shred plant residue. Plant and crop residue are gradually buried by cast material deposited on the surface and as earthworms pull surface residue into their burrows.

Source: Clive E. Edwards. Ohio State University

How do we get the Soil Food Web functioning?

The simple answer? Increase plant diversity on the farm and keep a living root in the ground at all times. This beneficial habitat for the entire food web will allow these microbes to build soil aggregates and restore the capacity of the soil to function.

Balancing the Carbon:Nitrogen ratio of the soil/plants/residue is crucial in creating a home (balanced diet) for the entire soil food web.

We would recommend a 15 species Full Season Cover to biologically jumpstart your soil.