ABSTRACT

Soil organic matter is all derived from living organisms such as plants, earthworms, slugs, snails, arthropods, nematodes, fungi and bacteria including actinomycetes. Many of the living organisms in the soil play an important part in the decomposition of the dead organic matter. Initially, finer and finer organic matter is produced but eventually just carbon dioxide, water and minerals are all that is left. The rhizosphere is a zone in the soil that is influenced by roots. Living roots change the atmosphere around them by using up oxygen and producing carbon dioxide. Furthermore, roots exude a variety of organic chemicals that are rich sources of food for many micro-organisms. Micro-organisms occur in greatly increased numbers and are more active when in proximity to roots. Most woodland trees have fungi covering their roots and penetrating the epidermis. Orchids and heathers have an even closer association in which the fungi invade the root and coil up within the cells.