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The world beneath our feet: Soil structure and amendment Part III

Jenny Wren

Toad, Worms, Wood Lice and Amending the Soil all have one thing in common – they are part of the Soil Food Web. The Food Web is written about frequently and is graphically described in the rhyme about The Old Lady Who Swallowed a Fly who knew large animals eat smaller ones, a brilliant explanation of The Food Chain or Web.

The Soil Food Web is a continuation of that web but too frequently it is ignored.

The Soil Food Web is really part of The Food Web. Compare how much we know about life above ground to that below. We don’t generally squirm when we see a crow feeding on carrion or when we see ourselves chewing a good steak (well, some do). We don’t spend much time considering it but we do sometimes squirm if we find a small slug in our salad or ants that have made their way into the house. I would too but truly those occurrences are indicators of healthy soil around you.

Creatures who unite our above ground web with those below ground, chickens, other birds, toads, mice, voles are important members of The Web. They live because of smaller creatures in the Soil Food Web and those smaller creatures living below ground are what keep our soil healthy. Knowing you have a healthy soil is more than squeezing a lump of soil in your hand to see if it is friable. It is also looking to see if you have the life that belongs there – earthworms, centipedes, ants, slugs. No life below ground and your soil is not healthy.

We cannot see the majority of the life that exists beneath the ground because it is microscopic but a good indicator of soil health is earth worms. According to Jeff Lowenfels and Wayne Lewis in their book about The Soil Food Web, there can be up to 50 earthworms in a square foot of soil. My garden used to have a healthy population of dew worms. Golfers hate them because they are the enemy of a carpet like lawn but they are a workhorse for aeration and incorporation of organic matter into the soil. My dew worm population seems to have depleted and I credit the balance I feel I have in the garden. I believe they may be the reason Toad is so chubby and why I have such a healthy bird population. If you have never seen dew worms, they are like an oversized earth worm and many would squirm at first sight. However watching a dew worm actively pulling leaves into the ground is truly a wonder. We have a brick patio and the Mountain Ash of course drops a lot of leaves in the fall. When I see a moving leaf slowly disappearing between the bricks I know there is a large worm at work under there. Watching a Robin haul a large worm out of the soil is another fun sight – almost as good as watching a fly fisherperson with a large salmon.

Worms and other small creatures such as protozoa extract their energy from the carbon in plant material. This is where we can see how plants are actually in control for without plants there is no food web. There is a lot of chemistry that goes on below soil level to weave the web between plant and animal life. Plants secrete exudates through their roots just as we perspire. This in turn is a catalyst and condition in which fungi and bacteria can thrive enabling the plants to absorb the nutrients they need to grow. It is interesting that these days, when you go to the nursery to purchase a tree or shrub, you will frequently asked if you would like ‘Mike’. Mike is not a person. It is a dried powder made up of dormant fungi, mycorrhiza which facilitate better growth. In a healthy environment with a balanced soil food web this is naturally present. Adding some to a depleted soil will usually assist in healthy root development for a plant. Plants have a symbiotic relationship with these fungi. The mycorrhiza use the plant secretions. The fungi grow creating conditions which facilitate easier absorption of essential nutrients for the plant.

The earthworms and protozoa in turn spread the fungi and bacteria created in these environment to other plants and areas of the garden. It is easy to see these fungi at work when walking in a forest. If you find a mossy bank and can gently lift the moss you will frequently see a mass of white – the threads of fungus doing their work. A native forest frequently does not have the depth of soil we cultivate in our garden so the fungi are easier to see. Larger fungus on tree trunks and rotting wood are working in the same way.

In a garden environment I like to create the healthy web naturally. It is not always easy in an urban setting where herbicides and pesticides might be used in abundance. However as individuals we can do our best and I like to think Toad is an indicator of that. Like a canary in the coal mine my toad I believe has given me a message.