Definition of Soil
Whitney (1982) Hilgard (1892) Dokuchaiev (1900) Joffe (1936): Soil is a natural body of mineral and organic constituents differentiated into horizons usually unconsolidated, of variable depth which differs among themselves as well as from the underlying parent material in morphology, physical makeup, chemical properties and composition and biological characteristics.
SSSA (1970):
(i) The unconsolidated mineral matter on the surface of the earth that has been subjected to and influenced by genetic and environmental factors of parent material, climate (including moisture and temperature effects), macro and microorganisms and topography, all affecting over a period of time and producing a product, that is “SOIL” that differs from the material from which it is derived in many, physical, chemical, biological and morphological properties and characteristics.
(ii) The unconsolidated mineral material on the immediate surface of the earth that serves as a natural medium for the growth of land plants.
Approaches of Soil Study
Two Concepts: One treats soil as a natural body, weathered and synthesized product in nature while other treats soil as a medium for plant growth.
1) Pedological Approach: The origin of the soil, its classification and its description are examined in Pedology. (From Greek word pedon, means soil or earth). Pedology is the study of soil as a natural body and does not focus on the soil’s immediate practical use. A pedologist studies, examines and classifies soil as they occur in their natural environment.
2) Edaphological Approach: Edophology (from Greek word edaphos, means soil or ground) is the study of soil from the stand point of higher plants. Edaphologists consider the various properties of soil in relation to plant production. They are practical and have the production of food and fiber as their ultimate goal. They must determine the reasons for variation in the productivity of soils and find means for improvement.
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