Soil Classification Lecture Notes (Fall 2024) PDF

R.W. Dirszowsky – Lecture Notes (Fall 2024) Page 33 Soil Classification Throughout history humans have used some kind of system to name and classify soils in ancient ti...

R.W. Dirszowsky – Lecture Notes (Fall 2024) Page 33 Soil Classification Throughout history humans have used some kind of system to name and classify soils in ancient times soil was “good” or “bad” or associated with a type of crop more recently soils have been described in terms of use for farming or else geological materials the concept of soils as natural bodies was first developed in Russia by V.V. Dokuchaev (1883) translated into German by K.D. Glinka (1917) and then into English by C.F. Marbut (1927) Marbut and others developed the first classification systems in the US and these were used in some form in Canada as well then related to aspects of climate, vegetation and parent materials and initially classified in these terms… Zonal – soils in which climate has played a dominant roll in their development Interzonal – soils in which factors other than climate have played a dominant roll Azonal – soils that are incompletely developed Basis of Classification Through the 20th century emphasis changed from the genesis of soils to physical properties that can be verified genesis is often difficult to know since varied soils can be produced especially if influenced by past climates over the long term systems based on observable and measurable properties are referred to as “morphological systems” by the 1970’s several national and international taxonomic classification systems were developed with specialized nomenclatures e.g. Soil Taxonomy (United States) and Canadian System of Soil Classification in most of these systems specific taxa are based on physical, chemical and biological properties as represented in diagnostic horizons these may be surface (epipedon) or subsurface horizons each has a list of characteristics that must be present to fit in group aside from several detailed differences, the US system is more comprehensive than the Canadian system, and focuses on the sub-surface ENV1011 – Soil Science Cambrian College - Environmental Technician R.W. Dirszowsky – Lecture Notes (Fall 2024) Page 34 Soil Properties Used for Classification Soil survey and classification is based on well-defined list of properties and horizon characteristics 1. Site Details Location and topography Grid reference and aerial photographs Landforms, hydrology Relief and elevation; local drainage, main rock formations/parent material, and geology depth below soil Vegetation and land use Description of dominant species, size and density of natural vegetation, cropping history, soil/land relationships 2. General Soil Surface stoniness, rock outcrops, erosion hazard, presence of salt, details Information of survey methods 3. Soil Morphology Horizon depths and thickness, moisture status, colour and mottling, structure, stone content, root size and distribution, horizon boundaries 4. Field Tests Bulk density, pH, carbonate content, textural analysis (hand method) 5. Laboratory Tests Textural analysis (mechanical analysis), carbon and nitrogen concentration, iron and aluminum concentration, water content at field capacity 6. Additional and Climate data, annual precipitation, mean monthly temperatures, clay specialized information mineralogy, moisture release data, soil mechanical properties, toxic materials, microbial biomass, organic matter fractionation Soil Horizons The definitions of taxa in soil classification systems are based on the kinds, degrees of development, and sequences of soil horizons and other layers in pedons “a soil horizon is a ‘layer’ of mineral or organic soil material approximately horizontal to the land surface that has characteristics altered by soil forming processes” a horizon differs from adjacent horizons in properties such as colour, structure, texture, consistence, and physical, chemical and biological composition the major mineral horizons are A, B, C the major organic (> 17% OC) horizons are L, F, H and O (or peat) subdivisions of horizons are labelled by adding lower case suffixes to the major horizon labels other layers defined are R (rock) , W (water) and IIC or IIIC etc. (non-conforming unconsolidated mineral layers) ENV1011 – Soil Science Cambrian College - Environmental Technician