Fao-unesco soil classification system pdf
Soil is a 3-dimensional body with properties that reflect the impact of 1 climate , 2 vegetation, fauna, Man and 3 topography on the soil's 4 parent material over a variable 5 time span. Unlike plants and animals, which can be identified as separate entities, the world's soil cover is a continuum.
In the early days of soil science, soil classification was based on the surmised genesis of the soils. The many soil classification schemes developed over the years reflect different views held on concepts of soil formation and mirror differences of opinion about the criteria to be used for classification.
In the 's, international communications intensified while the number of soil surveys increased sharply both in temperate regions and in the tropics.
The experience gained in those years and the exchange of data between scientists rekindled interest in the dynamics of the world's soil cover. Classification systems were developed, which aimed at embracing the full spectrum of the soil continuum.
In addition, emphasis shifted away from the genetic approach, which often contained an element of conjecture, to the use of soil properties as differentiating criteria. By and large, consensus evolved as to the major soil bodies which needed to be distinguished in broad level soil classification although differences in definitions and terminology remained. Compilation of the SMW was a formidable task involving collection and correlation of soil information from all over the world.
Soil Subunits were not defined as such but guidelines for their identification and naming were given.
Table 1 summarises the 10 sets, their dominant identifiers and the Reference Soil Groups within each set. SET 2 contains all man-made soils. These soils vary widely in properties and appearance and can occur in any environment but have in common that their properties are strongly affected by human intervention. SET 3 includes mineral soils whose formation is conditioned by the particular properties of their parent material. The set includes three Reference Soil Groups:. SET 5 holds soils that are only moderately developed on account of their limited pedogenetic age or because of rejuvenation of the soil material.
First and Second Level Classes of the FAO System with Simple Definitions
Moderately developed soils occur in all environments, from sea level to the highlands, from the equator to the boreal regions, and under all kinds of vegetation. High soil temperatures and at times ample moisture promote rock weathering and rapid decay of soil organic matter.
The Reference Soil Groups in this set have in common that a long history of dissolution and transport of weathering products has produced deep and genetically mature soils:. Redistribution of calcium carbonate and gypsum is an important mechanism of horizon differentiation in soils in the dry zone. Soluble salts may accumulate at some depth or, in areas with shallow groundwater, near the soil surface. The Reference Soil Groups assembled in set 7 are:.
SET 8 holds soils that occur in the steppe zone between the dry climates and the humid Temperate Zone. This transition zone has a climax vegetation of ephemeral grasses and dry forest; its location corresponds roughly with the transition from a dominance of accumulation processes in soil formation to a dominance of leaching processes. Set 8 includes three Reference Soil Groups:.
SET 9 holds the brownish and greyish soils of humid temperate regions. The cool climate and short genetic history of most soils in this zone explain why some soils are still relatively rich in bases despite a dominance of eluviation over enrichment processes.
Eluviation and illuviation of metal-humus complexes produce the greyish bleaching and brown to black coating colours of soils of this set. Set 9 contains five Reference Soil Groups:.
FAO/UNESCO System of Soil Classification
SET 10 holds the soils of permafrost regions. Cryoturbation also results in oriented stones in the soil and sorted and non-sorted patterned ground features at the surface. Note that the Reference Soil Groups in sets 6 through 10 represent soils, which occur predominantly in specific climate zones. Be aware, however, that not all soils in sets 6 through 10 are zonal soils, nor are soils in other sets always non-zonal.
Podzols, for instance, are most common in sub humid temperate climates set 9 but they are also found in the humid tropics; Planosols may equally occur in subtropical and steppe climates and Ferralsols may occur as remnants outside the humid tropics. In other words there are zonal and intrazonal Podzols, zonal and intrazonal Gleysols, zonal and intrazonal Histosols, and many more.
Young alluvial soils Fluvisols and soils in recent hillwash e. Cambisols are examples of azonal soils. The zonality concept helps to understand some of the diversity of the global soil cover but is a poor basis for soil classification.
The sets of Reference Soil Groups presented in this text may therefore not be seen as high level classification units but merely as an illustration how basic principles of soil formation manifest themselves in prominent global soil patterns. Mineral soils whose formation was conditioned by human influences not confined to any particular region.
What is FAO SOIL CLASSIFICATION? What does FAO SOIL CLASSIFICATION mean?
Mineral soils whose formation was conditioned by their parent material - Soils developed in volcanic material - Soils developed in residual and shifting sands - Soils developed in expanding clays. Mineral soils whose formation is conditioned by their limited age not confined to any particular region.
The diagnostic horizons, properties and materials used by the WRB to differentiate between Reference Soil Groups are described hereafter in Tables 2, 3 and 4; their full definitions can be found in Annex 2 to this text.
FAO soil classification
Note that a distinction must be made between the soil horizon designations used in soil profile descriptions and diagnostic horizons as used in soil classification. The former belong to a nomenclature in which master horizon codes H, O, A, E, B, C and R are assigned to the various soil horizons in a soil profile when it is described and interpreted in the field.
The choice of horizon code is by personal judgement of the soil surveyor. Some of the diagnostic horizons in the WRB soil correlation system are special forms of A- or B-horizons, e. Other diagnostic horizons are not necessarily A- or B-horizons, e.
Surface horizons and subsurface horizons at shallow depth. Its carbon content is intermediate between a mollic horizon and a histic horizon.
Note that the generalised descriptions of diagnostic horizons, properties and soil materials given in Tables 2, 3 and 4 are solely meant as a first introduction to WRB terminology. The exact concepts and full definitions presented in Annex 2 must be used for identifying diagnostic horizons, properties and materials in practical taxon identification.
See: Honna T. Yamamoto and K.
A simple procedure to determine the melanic index that is useful for differentiating Melanic from Fulvic Andisols. Pedologist, Vol. Mineral soils whose formation was conditioned by climate: sub- humid tropics. Mineral soils whose formation was conditioned by climate: arid and semi-arid regions. Mineral soils whose formation was conditioned by climate: steppes and steppic regions.
Mineral soils whose formation was conditioned by climate: sub- humid temperate regions. Mineral soils whose formation was conditioned by climate: permafrost regions.