Soil is the product of various factors functionally interrelated. S = F (CI, O, P, R, T) S = soil properties F = function CI = climate
O = organism, (biological activity), ACTIVE R = relief
P = parent material, PASSIVE T = time
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1. Parent Material:
Controls textural properties, e.g., quartzose materials give rise to sandy soils. Basic rocks and fine-grained sediments give fine textured soils. They have strong influence on young soils; influence diminishes with time. Iii general, there is weak co-relation between plant and other material and soils.
2. Relief:
Determines the thickness of the soil drainage and the amount of moisture in the soil.
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3. Time
Determines maturity.
4. Climate:
It has most profound effect. It affects soil directly by controlling weathering, percolation through the soil, and work of gradational agents; indirectly by influencing vegetation, humus formation and acidity.
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The same type of rock can give rise to very different soils depending on climate-basalt may give brilliant, red coloured highly weathered soil in the humid tropics or it may give a black tropical soil in semi-arid conditions.
5. Organism:
Includes higher plants, vertebrates, micro-organisms and mesofauna. They act as binders, lead to formation of cracks and air circulation.
They cause addition of organic matter, extraction of water and nutrients, their release and absorption and re-absorption.
Few mammals by their burrowing habits cause considerable mixing.
Micro-organism like actinomycetes (Streptomycetes) are very important decomposers of organic matter.
Algae, when in sufficient number, form a crust preventing soil erosion, contribute to organic matter and initiate “Carbon and nitrogen cycles.
Mesofauna like earthworms, nematodes, mites are concerned with ingestion and decomposition, transport material and in doing so produce passages which improve drainage and aeration.
Although all the factors have different influence, they all are interrelated in totality.