Case Study: Soils, soils, soils

Boring, boring, boring I hear you say but no, wait, you may have been missing something. Soil is so important because we use it to produce food, build houses, grow trees, improve water quality, regulate water flow, filter out harmful substances and maintain ecosystem stability. Here is some interesting info about soil.

Bugs

There are many millions of insect species in soil. In a pea-sized lump of soil there can be as many as 10 000 million bacteria, 10 million fungal spores, and 10 million algae as well as larger mites, worms, ants etc.

Many soil insects are beneficial. There are certain fungi (mycorrhiza) that help plants retrieve nutrients (e.g. phosphorus) from the soil. This can be especially important in Australian soils, which are often low in phosphorus. Other things like some nematodes and mites actually reduce pest species by feeding on them.

Colour

Did you know that soil colour can tell you about its fertility? Light-coloured soils are mostly low in nutrients while dark-coloured soils indicate lots of organic matter present. A reddish soil shows good drainage and aeration.

Texture and structure

These are two soil terms that are often confused. Texture is a measure of the ratio of sand:silt:clay in the soil. But structure is how these and the organic matter and air spaces in between are arranged. The key to a good soil structure is lots of organic matter. Organic matter and clay help hold all soil particles together. The spaces around the lumps of soil are just as important, as they allow air and water into the soil. A well-structured soil will have a range of soil clump sizes and a range of spaces in between.

pH

The most common chemical trait talked about in soils is pH. This is a measure of its acidity/alkalinity or, as some say, its sourness or sweetness. Most plants like a pH range of 5-8, so this is where you want your soil to be too. On the pH scale, 0-6 is acid, 8-14 is alkaline and 7 is neutral. Most soils in NSW are naturally acidic (pH 5 or below), which is why lime often has to be added for agricultural use. The pH of a soil will also affect the availability of nutrients to the plants and in many cases can make toxic aluminium more available.

So you see there is certainly a lot more going on beneath our feet than we realise.

Sourced from an article by Abigail Jenkins, NSW DPI.