Dirt, or more accurately, soil, is amazing stuff and something that we very much take for granted. But not all dirt/soil is not created equal. I've been fascinated with soil since I discovered how long and how much material it takes to make it.

For the sake of clarification, let's make a couple of distinctions.

Dirt - mainly mineral based; pebbles and finely ground rock.

Soil - mineral, plant, fungi and animal based.

It's easy to tell dirt and soil apart. Soil will usually be darkish in color and have a rich earthy smell. Dirt just tends to smell like dust.

There's a lot of dirt around the world, it's in plentiful supply - no worries there. The problem with dirt is that it's a filler and has very little nutrient content as its primarily composed of basic minerals - calcium, iron etc. While these are required to some degree by plants, the real life giving properties are in the soil.

Soil is a smorgasbord of nutrients; animal droppings and decaying plants and creatures add to its fertility. It contains a multitude of life forms including insects, fungi and bacteria - it's an ecosystem unto itself.

Because there's so much dirt around, we can tend to see it as a limitless resource; but so much of the dirt on this planet isn't really capable of sustaining life.

The soil/worm connection

I began to understand how much matter it takes to make soil when starting a worm farm. In that scenario, the worms break down the organic material leaving what is basically a very rich soil - worms are a crucial part of the soil ecosystem.

We put hundreds of pounds of waste into our worm farm during the first year and at the end of it still weren't able to fill the worm bin up with castings (worm poo). All that organic waste breaks down so much as it primarily consists of water.

Soil horizons

Soil layers are called horizons. The very top layer is called the O horizon, it's made of new and decomposing organic materials and basically acts as a mulch.  The "A" horizon below it is a mixture of rock particles and decomposed organic materials - the fertile soil. This can be a few inches to  to a foot thick. The B horizon is almost entirely rock material, plus some nutrients that have washed out of the A horizon. The C horizon is mainly bedrock in various states of weathering and extends to a depth of thousands of feet.

The fragile nature of soil

Only a very small percentage of our planet has soil suitable for sustaining high levels of plant life and the silly thing is we tend to build our houses in areas where this rich soil is. When our house was being built, I remember all the topsoil being scraped off the top of the subdivision and dumped in big piles - which the wind then went to work on, causing localized dust storms so thick that at times we could hardly see across the road.

We lose millions, perhaps billions of tons of top soil across the world each year that winds up in our oceans. Good quality soil tends to extend downwards just inches rather than feet  - and that's what sustains us; so it's crucial that we preserve what we have.

Threats to soil:

Acidification - usually happens through intensive watering and harvesting when certain nutrients and minerals are removed that alter the acid/alkali balance, or by using too much nitrogen-rich fertilizer.

Soil contamination - often contaminated by industrial chemicals. It can sometimes take many years for oils etc. to wash out of soil to the degree that plant life can grow again.

Desertification - this can sometimes be caused by drought, but also by general abuse where too much is taken out of the land without anything being put back into it. The land becomes infertile.

Soil erosion - once plant cover is removed, such as in the case of deforestation, the soil is no longer replenished with nutrients and is easily blown away or carried by rainwater runoff.

Salinity - where saline ground water comes to the surface, evaporates and leaves salts behind. This commonly occurs where deep rooted trees are cleared.

Things you can do to help save our soil

Even if you don't have a yard, we can all do our bit to go towards conserving our precious soil.

- Start a worm farm and return the casting to the earth

- Start up a compost pile

- Mulch; this not only saves water in your garden but protects the soil and adds to it

- Use natural fertilizers

- Plant more trees and deep rooted vegetation

- If you're moving soil from one area to another, try to do it on a calm day or cover up the pile

- Don't pour hazardous waste and toxic substances onto the ground e.g. gas and oil.

While "Peak Oil" has been getting increased media attention lately, a matter just as urgent is Peak Soil. While a life without oil is a disturbing concept, life without adequate fertile soil is downright frightening.