Diagnostic Horizons PDF

DIAGNOSTIC HORIZONS Cryic horizon - perennially frozen soil horizon with ice (on photo) or soil temperature permanently below Albi...

DIAGNOSTIC HORIZONS Cryic horizon - perennially frozen soil horizon with ice (on photo) or soil temperature permanently below Albic horizon 0°C. - bleached soil material washed out of iron, aluminium and humus by podzolization process. Ferralic horizon - eluvial horizon depleted in the fraction of clay, compounds of iron, aluminium – washed out - subsurface horizon resulting from long and by lessivage process. intense weathering. - if the ferralic horizon has less hematite and a more yellowish colour, it typically shows a higher bulk density and a lower porosity. Argic horizon - enriched with the clay fraction often also with iron compounds, which give it a colour Folic horizon browner than the parent material. - in many cases (e.g. due to erosion) argic - develops at the soil surface, under relatively horizon is directly below the humus horizon ‘dry’ environmental conditions (is saturated with water for - predominantly occurs where low temperatures inhibit the organic debris (litter) decomposition Calcic horizon rate (e.g. mountain areas, taiga etc.). - secondary accumulation of calcium carbonate - has a well-aerated organic material with visible in cracks, pores and on the surface of thickness of ≥10 cm stones. - numerous secondary carbonate concretions of spherical shape. Fragic horizon - non-cemented subsurface horizon with large soil aggregates. Roots and percolating water Cambic horizon penetrate the soil only in between these - increasing colour intensity and development of aggregates. soil structure in weathered limestones. - can overlap partly or completely with an argic - clay and iron accumulation in-situ in weathered horizon. acid rocks - pedogenical structure in slope deposits, enriched also with humus. Gypsic horizon - iron compounds accumulation and soil structure development in silty deposits - accumulations of secondary gypsum can be covering pieces of shists. visible in form of light in colour dots – concretions. - non-cemented surface or subsurface horizon containing accumulations of secondary Chernic horizon gypsum in various forms. - thick, dark, well structured humus horizon – - has ≥5% gypsum – on photo in form of often with high biological activity (crotovinas). crystals. - due to high fertility, soils with chernic horizon are often intensively cultivated. Lower plough boundary visible at 50 cm. Histic horizon - consists of poorly aerated organic material with thickness of ≥10 cm accumulated at soil Cohesic horizon surface. - subsurface horizon dominated by kaolinite. It is - its development is associated with found in tropical regions with seasonal climate waterlogged landscapes – wetlands, bogs, changes. peatlands. Hortic horizon - cemented by calcium or magnesium carbonate. Its massive or platy structure - is often found in allotment gardens. makes it resistant for penetration - humus horizon created by the human activities - also occurs as non-platy and non-massive of deep cultivation, intensive fertilization and/or nodular calcrete. long-continued application of organic residues. - its development results from intensive agricultural treatments, usually on a small spatial scale. Petrogypsic horizon - cemented horizon containing accumulations of secondary gypsum. Limonic horizon - these horizons are cemented, whitish and composed predominantly of gypsum. - strong accumulation of Fe by capillary rise in groundwater soils cause a cementation of mineral material – eg. Sand - is traditionally referred to as bog iron. Pieces Petroplinthic horizon of it have dark brown colour and behave like - is a continuous, fractured or broken layer of soft stones. material cemented by Fe (and in some cases also Mn) (hydr-)oxides. Evolved in tropical climates. Mollic horizon - traditional names for such horizons are 'laterite' or 'ironstone'. Fragments of laterite on - development of mollic horizon is often photo. associated with grass vegetation - well developed thick and dark humus horizon with high base saturation. - due to high fertility most of mollic horizons are Pisoplinthic horizon in agriculture use. On photo visible sharp lower - reddish or blackish concretions and nodules boundary made by ploughing. have occupy more than 40% of exposed area but can be hardly visible from distance. - contains a large amount of concretions and/or Natric horizon nodules that are at least moderately cemented by Fe (and in some cases also by Mn). - subsurface layer with distinctly higher clay - after the rain nodules and concretions of these content than the overlying layer and high horizons become more visible – especially in content of exchangeable Na. surface horizons and exposed scarps. - apart from illuvial concentration of clay has a columnar or prismatic structure at least in some parts. Protovertic horizon - in these horizons some shrink-swell cracks Panpaic horizon can be visible. - has swelling and shrinking clay minerals with - is an expression of soil formation in the past, some amount of wedge-shaped soil here buried by volcanic deposits. aggregates or some slickensides. - is a buried mineral surface horizon with a - wedge-shaped soil aggregates and significant amount of organic matter formed slickensides may not be immediately evident if before having been buried. On photo almost the soil is moist. black A horizon buried by slope processes on depth of 170–180 cm. - these horizons are common in agriculture landscapes. Some of them were ploughed in Salic horizon the past when they were on soil surface - it is - surface horizon or a subsurface horizon at a visible by sharp lower boundary. shallow depth that contains high amounts of readily soluble salts which can be visible on soil surface as white salt crust. Petrocalcic horizon - salt crystal can appear on aggregate surfaces after excavation from soil and exposition to the - petrified massive calcrete – extremely sun. cemented layers by secondary carbonates. Spodic horizon - subsurface horizon containing illuvial compounds of iron, aluminium and humus, diagnostic horizon for Podzols. - in most of these horizons, the upper part is characterized by dark illuvial organic matter, when lower is more brownish – coloured by illuvial Fe oxides. Tsitelic horizon - usually found in soils on lower slopes or in depressions. Characterized red colour is due to accumulation of Fe by lateral subsurface waterflow. - due to the low bulk density and the thixotropy, they may give the impression of andic properties, but they have neither a significant amount of allophanes and imogolites nor of Al- humus complexes. Umbric horizon - well developed thick and dark humus horizon with relatively low base saturation. - morphologically is very similar to mollic horizon – pH test on field can help with distinguishing it Vertic horizon - dominated by swelling and shrinking clay minerals, has slickensides and wedge-shaped soil aggregates. - wedge-shaped soil aggregates and slickensides may not be immediately evident if the soil is moist.