The soil is at the interface between the atmosphere and lithosphere (the mantle of rocks making up the Earth's crust). It also has an interface with the hydrosphere, i.e. the sphere describing surface water, ground water and oceans. The soil sustains the growth of many plants and animals, and so forms part of the biosphere. A combination of physical, chemical and biotic forces acts on organic and weathered rock fragments to produce soils with a porous fabric that contain water and air (pedosphere). We consider soil as a natural body of mineral and organic material that is formed in response to many environmental factors and processes acting on and changing soil permanently.
Figure 1.1.1. Compartments of a landscpape.
Because soil is important for cultivation and agricultural production, soil fertility and productivity are important issues to address. Detailed pedological knowledge is useful for land evaluation purposes, i.e. the classification in fertile productive soils and less valuable soils. Soils are an integral part of landscapes and the knowledge of the distribution of different soils helps to preserve a high standard in environmental quality. For example, site specific management cannot be developed without detailed knowledge of soils. Critical sites, e.g. shallow hillslope soils prone to erosion and leaching of nutrients, can be identified using pedology. Soil surveys furnish basic inputs to soil conservation planning and provide information used in equations for predicting soil loss and water pollution under various management practices on different soils.
Some definitions are given, which are closely related to soil science and pedology:
Pedology: The interpretation, mapping, and classification of soil based on soil genesis.
Pedon: A pedon is the smallest volume that can be recognized as a soil individual. It has three dimensions and its area ranges from 1 to 10 square meters, depending on the variability in the horizons. The shape of the pedon is roughly hexagonal. A soil volume that consists of more than one pedon is termed a polypedon.
Ped: Peds are soil aggregates which are recognizable in the field because they are separated by voids and natural planes of weakness. They should persist through cycles of wetting and drying, as distinct from the less permanent aggregates.
Pedogenesis: The process of soil formation as the integral result of the combination of soil forming factors (climate, parent material, relief, organisms, time).
Soil classification: The grouping of different soils into classes on the basis of one or more criteria. A class is a group of individuals or units similar in selected properties and distinguished from all other classes by differences in these properties.
Information provided by: http://www.soils.wisc.edu