Besides being the source for the entry of nutrients and water into plants, the soil is the medium for the detritus food chain: nutrients released in detritus are decomposed by various soil microbes like bacteria, algae, fungi, protozoa, etc., bound in or on soil particles, and taken back into plants through their roots. Soil (mud) is also the main source of nutrients for all aquatic plants (hydrophytes), roofed or submerged or free-floating. In addition, soil is the means of support for all terrestrial organisms : plants are anchored to the soil by their root systems ; animals walk upon it and are supported by it, as many animals like nematodes, polychaetes, arachnids, insects, rodents, etc.
, live under the soil. The word soil is derived from a Latin word ‘solum’ meaning earthy material in which plants grow. The science which deals with the study of soil is called soil science, pedology (pedos-earth), or edaphology (edaphos-soil).
The study of soil is helpful in practices of agriculture, horticulture, forestry, etc., such as cultivation, irrigation, artificial drainage and use of fertilizers. Pedology is also useful in sciences like geology, petrology, mineralogy, palaeobotany and palaeozoology. A fully developed or mature soil is that state of soil that has assumed the profile features (i.
e., succession of natural layers), characteristic of predominant soils on the smooth uplands within the general climate and botanic regions in which it is found (Marbut, 1926). According to Dokyachev (1879), the first soil scientist, the soil is a result of the actions and reciprocal influences of parent rocks, climate, topography, plants, animals and age of the land.