A spadeful of soil for garden may look very simple, innocuous substance. But it is, in fact, of such enormous complexity that it is doubtful if mankind will ever fully understand it. First of all, if it is good soil, it is filled with life. In every teaspoonful of soil there are millions of bacteria – bacteria of numerous species as well as algae, microscopic animals, the mycelium of fungi, and viruses. In larger quantities of good soil you are sure to find worms and the larvae of numerous beetles and other insects. It has been calculated that there are from five to ten tons of living matter in every acre of soil.
The interrelationships of these various animals and plants are of great complexity. There are long and involved food chains, and subtle mutually beneficial arrangements. There are chemical processes of such complexity that no scientist has ever been able to duplicate them in his laboratory. For example, there are five species of bacteria that we know of which can fix nitrogen from the air and convert it into the type of amino acid which can make protein for plants and ultimately people. Two other species of bacteria have the baleful effect of turning useful nitrites and nitrates, that could have been used by plants, into free nitrogen gas again; three species can turn ammonia into nitrites; another can turn nitrites into nitrates which plants can use; and a huge array of bacteria, fungi and actinomycetes turn protein and other dead organic matter into ammonia. That simple spadeful of soil is a chemical factory of sophistication that no human chemist has ever been able even to approach.
The origins of soil
Fundamentally, soil is rock that has been pulverized by such agents as heat and cold, water and wind, and, very importantly, has been subjected to the eroding effect of lichens, bacteria, algae and other living creatures. The hardest rock in the world, as long as it is exposed to light, is being gradually gnawed away by plant life. For the purposes of the gardener, although a geologist might disapprove, it is enough to say that most of the land surface of the Earth consists of a layer of soil lying on top of rock. Between the two is an intermediate layer known as subsoil, which is rock in the process of being broken down by natural forces. Some soils are the direct products of the rock underneath them; others were brought to where they are by other forces. They may have blown there; like the Ioess soils of North America and China, been carried there by glaciers, like much of the soil in North America and much of the soil north of the Thames in Britain, or been washed there by water, like many sols in river valley.
Types of soil
To, the practical gardener the origin of his soil is of interest, but not vitally important. What is important to the gardener is the nature of his soil, wherever it came from: Whether it is light, meaning composed of large particles like sand; heavy, meaning composed of very small particles like clay; or something in between. It is important to know: whether it is that rare commodity, organic soil, which means it is composed of decaying vegetable matter; whether it is acid or alkaline sand is inclined to be acid, clay alkaline; whether it is naturally well drained or not; what lies underneath it – soil above chalk or limestone is vet-) likely to be alkaline. Fortunately, whatever your soil: is like, you can improve it. There is scarcely a soil in the world that will not grow good crops of some sort if it is properly treated. There are many types of fertilizers to assist with this, but I strongly suggest using an organic garden fertilizer, especially ones you can make at home like compost or organic liquid fertilizer. Excess acidity is easily remedied by adding time; excess alkalinity by adding compost or manure. Water logging can always be cured by drainage. Trace clement deficiencies can be cured simple by adding the missing trace elements.