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Soil properties that can be measured quantitatively are used in this classification system – they include: depth, moisture, temperature, texture, structure, cation exchange capacity, base saturation, clay mineralogy, organic matter content and salt content. There are 12 soil orders (the top hierarchical level) in soil taxonomy.
The pore space of soil contains the liquid and gas phases of soil, i.e., everything but the solid phase that contains mainly minerals of varying sizes as well as organic compounds. In order to understand porosity better a series of equations have been used to express the quantitative interactions between the three phases of soil.
American soil scientist Hans Jenny published in 1941 [128] a state equation for the factors influencing soil formation: S = f(cl, o, r, p, t, ...) S soil formation; cl (sometimes c) climate; o organisms (soil microbiology, soil mesofauna, soil biology) r relief; p parent material; t time; This is often remembered with the mnemonic Clorpt.
Diagnostic properties are typical results of soil-forming processes or reflect specific conditions of soil formation. Diagnostic horizons are typical results of soil-forming processes showing a minimum thickness and therefore a horizontal appearance. The diagnostics have names (e. g. argic horizon, stagnic properties, fluvic material). [1]
Soil Profile on Chalk at Seven Sisters Country Park, England. Pedology (from Greek: πέδον, pedon, "soil"; and λόγος, logos, "study") is a discipline within soil science which focuses on understanding and characterizing soil formation, evolution, and the theoretical frameworks for modeling soil bodies, often in the context of the natural environment. [1]
A soil scientist examining horizons within a soil profile. Soil science is the study of soil as a natural resource on the surface of the Earth including soil formation, classification and mapping; physical, chemical, biological, and fertility properties of soils; and these properties in relation to the use and management of soils. [1]
Since the origin of agriculture, humans have understood that soils contain different properties which affect their ability to grow crops. [4] However, soil science did not become its own scientific discipline until the 19th century, and even then early soil scientists were broadly grouped as either "agro-chemists" or "agro-geologists" due to the enduring strong ties of soil to agriculture.
The Unified Soil Classification System (USCS) is a soil classification system used in engineering and geology to describe the texture and grain size of a soil. The classification system can be applied to most unconsolidated materials, and is represented by a two-letter symbol. Each letter is described below (with the exception of Pt):