Thursday, 7 July 2011

worm nests, fermented compost and building highly humic soil

If you saw the last post "microbes in the community" you'll note we had a lot of interest in our pics of worm nests, of which i promised to explain a little more...

"worm nests?" i hear you ask "but worms don't make nests, do they?"

well, maybe they don't, but when a young child sees the likes of this:

 then you have to ask yourself what else you'd call it!

Of course, this is all part of a process and that process we call "fermented compost".  Why fermented compost?  Simply put, we take our (highly nitrogenous) kitchen waste and ferment it with microbes, before adding it to the soil, for the worms to munch away at.

Compost worms (Eisenia fetida) are different than earth worms, firstly. They are commonly known as redworm, brandling worm, tiger worm and red wiggler worm, but are a species of earthworm adapted to decaying organic material. When roughly handled, an eisenia fetida exudes a pungent liquid, thus the specific name foetida meaning foul-smelling. This is presumably an antipredator adaptation.

 Although very simple organisms, worms can be thought of as "cows of the soil" in that they require bacteria in their guts, in order to process the organic matter they consume (along with a grit-like calcium carbonate substance they produce through internal glands).  In studies of soil the world over, scientists have found that where there is a lack of soil bacteria, worms populations are sparse.  Conversely, where healthy worms populations exist, the soil bacteria is plentiful and healthy.  This explains, in part, why fermented compost is so attractive to these little soil-recyclers and why, in a bacteria-rich resource such as fermented compost, they find their way in, eat plentifully, colonise, reproduce and turn the fermented compost into a nursery, replete with cocoons (worm eggs) and white baby worms, as you can see from the pic of the worm nest above.

To give an idea of scale, here are some pictures which zoom in from the spade level, to the close-up, where a 50 pence piece is shown.

As a point of note, that white substance you can see near the 50p is a product of fermentation, specifically a casein (cheese-like) material which is produced by Lactic Acid Bacteria - the very same lactic acid bacteria responsible for preserving Wooly Mammoths in the permafrost regions of Northern Europe.  For an elegant visual explanation of how Wooly Mammoths get preserved, be sure to check out the National Geographic Article here.

As you can see in the above pics, the white baby worms are plentiful.  Human hair gives an idea of the scales involved - you can even make out the tiny worm eggs (cocoons) and how the soil particles are sticking together, thanks to the humic content of their casts.

These photos were taken about 4 weeks after burying the fermented compost in a trench in the soil - half way through the 8 week process (in warmer weather - in colder weather it takes from 10 - 13 weeks for the fermented compost to be fully consumed by the worms).  You can think of these compost worms as a pioneer species, because after the compost worms have done their work, earthworms come in to colonise the now organically rich soil.

Indeed, as these later pics show, the baby worms soon become healthy adult worms, to continue the process:

Benefits of Humus

• Humus can hold the equivalent of 80 to 90 percent of its weight in water, so soil rich in humus is more drought-resistant.

• Humus is light and fluffy, allowing air to circulate easily, and making soil easy to work.

• The sticky gum secreted by microbes while forming humus hold soil particles together in a desirable crumb structure.

• Humus is extremely effective at holding mineral nutrients from being washed away in rain or irrigation water, and in a form readily available to plants. Ample reserves of humus also provide additional plant nutrients in times of need.

• Humus is able, because of its biochemical structure, to moderate excessive acid or alkaline conditions in the soil-a quality known as buffering.

• Many toxic heavy metals can be immobilized by soil humus, and prevented from becoming available to plants or other soil organisms.

• Although the color of humus can vary, it is usually a dark brown or black color, which helps warm up cold soils quickly in the spring.

In the next blog post, i'll show you how to make your own fermented compost system, so you too can start to make your own worm nests!

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