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The AASHTO Soil Classification System was developed by the American Association of State Highway and Transportation Officials, and is used as a guide for the classification of soils and soil-aggregate mixtures for highway construction purposes.
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):
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] The classification comprises two levels: The first level has 32 Reference Soil Groups (RSGs).
The second number ("P value") is the percentage by weight of phosphorus pentoxide P 2 O 5. The third number ("K value") is the equivalent content of potassium oxide K 2 O. [3] For example, a 15-13-20 fertilizer would contain 15% by weight of nitrogen, 13% by weight of P 2 O 5, 20% by weight of K 2 O, and 52% of some inert ingredient.
Soil sealing or soil surface sealing is the loss of soil resources due to the covering of land for housing, roads or other construction work. [1] Covering or replacing the topsoil with impervious materials like asphalt and cement as a result of urban development and infrastructure construction paired with compaction of the underlying soil layers results in the mostly irreversible loss of ...
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Soil texture triangle showing the USDA classification system based on grain size. For soil resources, experience has shown that a natural system approach to classification, i.e. grouping soils by their intrinsic property (soil morphology), behaviour, or genesis, results in classes that can be interpreted for many diverse uses.
These standards are adopted by the NCWM and published in Handbook 44: Specifications and Tolerances and Other Technical Requirements. NCWM utilizes special committees called National Type Evaluation Program Sectors to develop the technical policies, checklists and test procedures that are used for the evaluation and certification process.