Soils of the European Union - European Soil Portal - Europa

a. in more than 50 percent of the soil mass; orb. in 100 percent of the soil mass below any surface horizon.Field identification. Iron and manganese (hydr)oxides in soils with gleyic properties are redistributed to the outside of thepeas and towards the soil surface from where oxygen is derived. The resulting colour pattern (reddish, brownish oryellowish colours near the ped surface or in the upper part of the profile, together with grayish/bluish colours in the insideof the peas or deeper in the soil) indicates if gleyic conditions occur. Also, the dipyridyl test often gives a good indication ifferric iron is present in the soil solution.PermafrostDefinition. Permafrost is a layer in which the temperature is perennially at or below 0°C for at least two consecutive years.Secondary carbonatesGeneral description. The term secondary carbonates refers to translocated lime, soft enough to be cut readily with a fingernail, precipitated in place from the soil solution rather than inherited from a soil parent material. As a diagnostic property itshould be present in significant quantities.Field identification. Secondary carbonates must have some relation to the soil structure or fabric. Secondary carbonateaccumulations may disrupt the fabric to form spheroidal aggregates or 'white eyes', that are soft and powdery when dry, orlime may be present as soft coatings in pores or on structural faces. If present as coatings, secondary carbonates cover 50percent or more of the structural faces and are thick enough to be visible when moist. If present as soft nodules, theyoccupy 5 percent or more of the soil volume. Filaments (pseudomycelia), which come and go with changing moistureconditions, are not included in the definition of secondary carbonates.Stagnic propertiesGeneral description. Soil material has stagnic properties (from L. stagnare, to flood) if it is, at least temporarily, completelysaturated with surface water, unless drained, for a period long enough to allow reducing conditions to occur (this may rangefrom a few days in the tropics to a few weeks in other areas), and show a stagnic colour pattern 14 .Diagnostic criteria. Reducing conditions are evident by:1. a value of rH in the soil solution of 19 or less; or2. the presence of free Fe2 + as shown by the appearance of either:a. a solid dark blue colour on a freshly broken surface of a field-wet soil sample, after spraying it with a 1%potassium ferric cyanide (K 3 Fe(III)(CN) 6 ) solution; orb. a strong red colour on a freshly broken surface of a field-wet soil sample after spraying it with a 0.2% a,a,dipyridyl solution in 10% acetic acid; and3. an albic horizon or a stagnic colour pattern either:a. in more than 50 percent of the soil volume if the soil is undisturbed; orb. in 100 percent of the soil volume if the surface horizon is disturbed by ploughing.prevail due to iron sulphides. In calcareous material whitish colours are dominant due to calcite and/or siderite. Sands areusually light grey to white in colour and often also impoverished in iron and manganese. The upper part of areductomorphic horizon may show up to 5 percent rusty colours mainly around channels of burrowing animals or plantroots.14 A stagnic colour pattern shows mottling in such a way that the surfaces of the peas (or part of the soil matrix) are lighter(one Munsell value unit or more) and paler (one chrome unit or less) coloured, and the interior of the peas (or parts of thesoil matrix) are more reddish (one hue unit or more) and brighter (one chrome unit or more) coloured than the nonredoximorphicparts of the layer, or of its mixed average. This mottling pattern may occur directly below the surfacehorizon or plough layer, or below an albic horizon.82