Monday, 21 May 2012

Soil Soul!


I am constantly learning and evolving, and have many more questions that hopefully I will find the answers to and post on this page.

Documenting my intimate and sometimes overwhelming relationship with soil and all the information that goes with it!
This is my online Guts, digesting all the knowledge about Yummy Soil and its complex history, structure and web!

Get Your Hands Dirty!!!


The first thing I will say is: SOIL IS LIVING! You cannot see it, but each time you take a step you are standing on a complex web of creatures and critters that are all performing functions within a Soil Food Web. Most of the soil life is within the first 10 centimeters of soil, housing and harboring centipedes, springtails, ants, slugs, ladybird beetle larvae and countless bacteria and fungi. There can be up to 50 earthworms in a square foot of soil, and just a single teaspoon of healthy soil contains a billion invisible bacteria, several yards of fungal hyphae (the fungal strands underground that give rise to the fruiting bodies we know as mushrooms) and several thousand protozoa (single celled organisms that feed on bacteria). 

One integral thing when talking about the Soil Food Web is talking about exudates. Most people do not realize that the energy gained from plants through photosynthesis is actually converted into chemicals that they secrete through their roots. These chemicals are called exudates. They are carbohydrates/sugars and proteins that are excreted by the roots into the rhizosphere (the place directly outside the roots). The rhizosphere is like a central hub for soil activity, as bacteria and fungi feed off the exudates. If you think of perspiration being a humans exudate, and the surface of the skin being the rhizosphere it makes things a little easier to imagine!
Exudates actually 'wake up' and attract beneficial bacteria and fungi. There is soil life constantly competing for these root secretions, which means there is a constant mix of diverse soil organisms present within this area. Whatever the bacteria and fungi do not need to absorb as nutrients, they release as wastes, which the plants take up into their roots. This is like going to the local organic shop for our nutrients, rather than to a supermarket far away for poor quality foods. Because all this is happening in the rhizosphere, it means that nutrients become readily available when and where they are needed!
Nutrients are preserved within the bodies of soil life and released when that organism dies or waste products are produced. This process is called immobilization. It means that nutrients are immobilized inside all of the critters, bacteria and fungi.
Now you might start to realize something.... without PLANTS the soil life diminishes! If there are no plants there are no exudates and therefore there is no thriving soil life around the rhizosphere. Plants create healthy soil life! A really amazing fact is that plants can control the amount and different kinds of fungi and bacteria which are attracted to them, depending on the kinds of exudates they produce. Plants are pretty smart, they may not be able to move, but they have been around long enough to adapt and have found many ways of drawing the things they need to them instead. 

Soil Pacman!
(what eats what within the soil) 

Exudates are secreted =====> Bacteria and Fungi Feed on Exudates =====> Nematodes and Protozoa feed on Bacteria and Fungi =====> Larger critters like Centipedes and Mites feed on Nematodes and Protozoa 

The soil food web is kept healthy and pathogenic bacteria is kept at bay while everything is in a balanced relationship, competing for exudates. The fungal strands (hypae) form a mat (called mycelium) that can wrap around roots and protect plants from pathogenic fungi and bacteria. Mycorrhizal fungi establish themselves in a symbiotic relationship with plant roots, providing them with nutrients delivered straight to the site that is needed.

"Ultimately, from the plants perspective anyhow, the role of the soil food web is to cycle down nutrients until they become temporarily immobilized in the bodies of bacteria and fungi and then mineralized" - 'Teaming with Microbes' Jeff Lowenfels & Wayne Lewis 

Disturbed soils will have more bacteria than fungi. Forest soils have 10 times the amount of fungi than bacteria, as fungi can break down lignin, the substance that differentiates trees from plants and creates bark. 

...more coming soon...

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