The difference between soil and dirt is life. Dirt is lifeless, soil is full of life. As a farmer, grower, or back yard gardener we are really in the business of building and maintaining soil, and if we do this well almost everything else takes care of it self.
What does healthy soil look like?
It has text and colour of chocolate cake, it had a sweet smell and life (worms, mites and other larger bugs) should be visible to the naked eye (and millions of smaller not so visible bugs).
So how do we make healthy soil?
The building blocks of soil are sand, silt and clay. A soil with a disproportionate amount of any of these will has different physical characteristics, and getting this balance right is important. Too much clay will result in poor drainage, too much sand will provide poor moisture retention. There is a lot of good information (for instance the Victoria Agriculture Department website http://vro.agriculture.vic.gov.au/DPI/Vro/vrosite.nsf/pages/soilhealth_toolbox) available on the benefits and problems the different compositions afford, soil pH testing and management, etc, it can be confusing, I know I get confused with all the terminology and soil amendments. There are situations where significant soil amendments may be required to set the basis for great soil, but in my experience almost all problems can be resolved simply and relatively quickly by the regular addition of good quality compost and managing the soil to build it's carbon content.
At our farm the soil tends to be rich in clay.
Most experts will tell me to add vast quantities of sand or lesser quantities of gypsum (calcium sulphate) to breakdown the clay and improve our soil structure. But in Australia gypsum is mined and we try very hard to reduce are carbon footprint. A simpler, more natural approach is to add carbon to the soil by adding good quality compost or well rotted manures, keeping the soil covered by mulch and avoiding the use of pesticides and herbicides will have devastating effects on subterranean life.
So in practical terms what does this actually mean? Well we create new garden beds firstly by laying down cardboard or paper on top of usually grass. Then because we have a lot of dead wood around the farm this is collected and placed onto of the base then fill the bed with quality compost, a layer of straw and more compost. The cardboard reduces (almost eliminates!) the weed load, the existing weeds and grass will decompose linking the existing soil base with the new. Over time the wood will decompose releasing carbon and more nutrients into the soil, and in the shorter term the straw and compost will create super nutrient rich soil and a happy haven for beneficial bugs and life in no time at all.
On existing beds we regularly ( 3 to 4 times per year) add a good layer of compost and always keep the bed covered with mulch or a cover crop, a crop grown purely to cover the soil which is then returned back to the soil when the bed is needed. And importantly we minimise soil disturbance, we rarely till the soil. Trees and perennials received at least 4 times a year fresh compost to the drip line and mulched. Do this and I guarantee you will have carbon rich super healthy soil supporting the healthy and vigorous growth of vegetables, plants, flowers and trees. Reducing the need for expensive fertilisers, reduce plant loss, less issues with pests and improved water retention.
How is soil the secret of life? As Jack Palance said in the movie "City Slickers" with Billy Crystal,
Curly: You know what the secret of life is? Mitch: No, what? Curly: (holds up his leather gloved hand and points his index finger) This. Mitch: Your finger? Curly: One thing, just one thing. Mitch: That’s great, but what’s the one thing? Curly: That’s what you’ve got to figure out.