So far we have focused on soil structure the chemicals. The trend today, is to take a piece of land, strip the top soil and build on the sub soil. Then to replace the top soil for landscaping, they bring in what they call “sandy loam”. This is usually mostly sand with minimal loam. It looks good and is easy to dig for a garden (which is why it’s a favorite with landscapers) but poor when it comes to moisture retention and fertility.
The plants you planted that were surviving in wintwer, wilt and die in summer. The soil just can’t retain water. The problem is easily fixed with the addition of humus. Leaf litter, lawn clippings or even fine bark mulch will assist with moisture retention and as they decompose in the soil, will realease valuable nutrients, however they will break down very slowly because your soil is lacking in the naturally occurring organisms that decompose this material, recyling the nutrients.
Soil is not just sand fibre and a few chemicals; it is a living environment with all sorts of organisms, from visible sized insects to microscopic ones, all interacting together. To do this effectively they need a warm moist environment. The process almost stops when the soil temperature drops to zero and when it tops 35ºC but peaks around 15ºC.
These organisims perform one or more of three functions:
- Decocmposition – the rotifers – they consume material and release nutrients back into the soil, in a form that can be used by the plants. Unfortunately they are often not too particular which material they consume and can consume living and dead material, causing harm if not in balance with the other organisms. These are the bacteria, fungi and many different types of nematodes (worms) and insects.
- Predators – these organisms prey on others, keeping the system in some sort of balance. Some predators can also feed on plant material when food is in short supply.
- Aerators – the beneficial organisms usually perform best when there is oxygen present and to aerate the soil requires organisms to create tunnels for air flow and drainage. Excess water can also prevent soil oxygen.
When these organisms are in balance your garden will flourish but you can’t buy them from the garden shop. They have to be grown on site and the fastest way is in compost.