Monday, July 27, 2015

The Soil Food Web

"We know more about the movement of celestial bodies than about the soil underfoot.” ---Leonardo da Vinci

Below is a copy and paste from the presentation found here.  This serves as a excellent introduction.  Keep in mind as one is reading that the Soil Food Web is crucial to the health of the Earth, all plants, animals, humans, economy, society, the water supply, weather, etc.  The Soil Food Web can be destroyed by various means (including most if not all methods of tilling).  I think it is time to come to terms with the statement of fact that our post-modern industrial agricultural practices are unenlightened.  And our economy/food system is full of greed and causing untold suffering to the inhabitants of the Earth.  

But it doesn't have to be this way. There are ways of growing food without even having to till. And there is an obligation to regenerate and rebuild soil as we grow for the sake of future generations. And because soil is so essential to human life there is a moral obligation to educate every single person on this Earth as to the importance of soil, so that they can make clear decisions as to how they are going to treat it, who they are going to let take care of it, and what they are going to do to help preserve and save it.  If anything why not learn about soil?  This is where our bodies come from and this is where they are going.  Its in the Bible.  And it is intellectually stimulating, not to mention wonderful to learn about soil.  Da Vinci craved what we have learned.  

Without further ado here is a summary of the Soil Food Web:

Role of Plants in Soil Food Web

• Provide up to 60% of their photosynthetically fixed carbon dioxide as food to soil organisms through their roots as root exudates (sugars, amino acids, proteins, shed root cells)
• Provide large quantities of plant matter to soil (food for the food web)
• By providing a rich source of exudate foods, plant roots are
surrounded by a thin layer of intense biological activity – the
rhizosphere – where most soil biology is found
• By selectively secreting specific foods a plant can stimulate specific organisms to grow and perform a required function for the plant (facilitated by high biodiversity)
• By regulating microbial growth in the rhizosphere, plants exert a very sophisticated influence on the structure of soil food webs and
patterns of nutrient flow


• One acre of healthy soil contains the weight of a cow in bacterial biomass
• One gram of healthy soil contains over 25,000 species and a billion individual bacteria
• High bacterial biodiversity is required to sustain soil functions under a variety of soil conditions
• Engage in nitrogen fixation (rhyzobia, Azotobacter), chemical detoxification (pseudomonads), promoting root growth and mycorrhizal associations
• Decompose organic matter and dissolve minerals and hold these nutrients
• Cover leaf and root surfaces to provide pathogen protection
• Secrete polysaccharide glues that stick soil particles together, increase water holding capacity and improve soil structure
• Serve as a primary food source for protozoa and bacteria-feeding
nematodes that (bacterial nutrient cycling channel)
• While most bacteria are beneficial, a small number are plant pathogens and usually occur in unhealthy and unbalanced soils
• Recent research has discovered numerous bacteria species inside plants and performing beneficial functions

• Important decomposers of high-carbon and resistant materials (lignins, woody materials) – including toxic organic chemicals
• Efficiently retain nutrients/micronutrients in their biomass and prevent them from leaching (N, P, S, Ca, Fe and others)
• Build soil structure by holding soil particles (glued by bacteria) together in aggregates with their long hyphal strands
• Improve air and water infiltration and the water holding capacity of soil
• A small number are pathogenic in contrast to large numbers of beneficial fungi that perform essential soil functions, including suppression of pathogenic species and the soil conditions permitting their appearance
• Can trap and digest nematodes
• Serve as a food source for fungal feeding nematodes and microarthropods that then excrete plant available nutrients (fungal nutrient cycling channel)
• Easily damaged by high-till and chemical agriculture
(supplement via Martin Crawford.  Recently it was discovered that fungi through their networks can move nutrients such as nitrogen, from overstocked areas to under-stocked areas via a structure called mycorrhiza

Soil Protozoa
• Single-cell flagellates, amoebae and ciliates living in water films on soil and organic particles, feed on bacteria and small bits of organic matter
• Feed almost exclusively on bacteria and in this process take in more nitrogen and nutrients than they need and excrete these in plant available form (Key discovery by Elaine Ingham in the 1980s) NUTRIENT CYCLING RATES are proportional to protozoa populations.
• Activity and movement helps maintain soil structure

Soil Nematodes
• Small round worms living in water films, inside plant roots and inside insects or their larvae
• Movement through soil spreads bacteria and fungi
• Classified as bacterial, fungal or root feeders - or as predators
• Participate in both bacterial and fungal nutrient cycling channels
• Provide food for other soil fungi, insects and worms

. . And The Rest . . .
• Mites
• Small insects
• Worms
• Centipedes, millipedes

Biology Releases Nutrients
• Available nutrients may be lacking
• A reserve of nutrients (total extractable) exists in MOST soils that are more than adequate to grow any plant.
• ACTIVE, functioning organisms must be present to move nutrients from one pool to the next.
• Organisms killed by pesticides or high levels of inorganic fertilizers must be replaced

What Compost Can Do
• Suppress Disease (no more pesticides!)
• Retain Nutrients (stop run-off, leaching)
• Make Nutrients Available at rates plants
require (eliminate fertilizer)
• Decompose Toxins
• Build (re-build) Soil Structure
• Reduce Water Use, increase water holding
capacity, rooting depth
• Supports and restores soil foodweb health

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