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Before classification: profile description

Before classification: profile description

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SOIL ATLAS OF ASIA
2ND EDITORIAL BOARD MEETING
RURAL DEVELOPMENT ADMINISTRATION, NATIONAL INSTITUTE OF AGRICULTURAL SCIENCES,
JEONJU, REPUBLIC OF KOREA | 29 APRIL – 3 MAY 2019

SOIL ATLAS OF ASIA
2ND EDITORIAL BOARD MEETING
RURAL DEVELOPMENT ADMINISTRATION, NATIONAL INSTITUTE OF AGRICULTURAL SCIENCES,
JEONJU, REPUBLIC OF KOREA | 29 APRIL – 3 MAY 2019

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Before classification: profile description

  1. 1. Before classification: PROFILE DESCRIPTION!!!
  2. 2. The capital letters like H, O, A, E, B, C and R represent the master horizons and layers of soils. The capital letters are the base symbols to which other characters are added to complete the designation (i.e. 2Btg1). Most are genetic soil horizons, reflecting a qualitative judgement about the kind of changes which have taken place. Genetic horizons are not equivalent to diagnostic horizons, although they may be identical in soil profiles. Diagnostic horizons are quantitatively defined features used in classification. MASTER HORIZONS AND LAYERS
  3. 3. Code Determination Mineral horizons A Surface or near-surface mineral horizon with some organic accumulation, usually a darker colour than underlying horizons and/or smaller clay content than underlying horizons. E A near-surface mineral horizon characterized by a loss of clay, iron, aluminium, or some combination of these; usually lighter in color (higher value and/or lower chroma) than the overlying A and underlying B. B A mineral horizon characterised by one or more of the following: a concentration of clay, iron, aluminium, organic material or several of these; a structure and/or consistence unlike the horizons above and below; stronger colours (higher chroma and/or redder hue) than the horizons above and below. C Consolidated or unconsolidated material, usually partly weathered, little affected by pedogenic processes. R Hard bedrock that cannot be cut with a spade. Organic horizons O Horizons dominated by organic material consisting of undecomposed organic materials that have accumulated on the surface of either mineral or organic soils. O horizons are not saturated with water for prolonged periods. H These horizons dominated by organic material formed from accumulations of undecomposed or partially decomposed organic material. All H horizons are saturated with water for prolonged periods, or were once saturated but are now drained artificially. MASTER HORIZONS AND LAYERS full list in FAO book page 67
  4. 4. Suffix Short description Used for b Buried genetic horizon mineral horizons c Concretions or nodules mineral horizons g* Stagnic conditions / *USA strong gley no restriction h Illuvial accumulation of organic matter mineral horizons i/*ss Slickensides / *USA mineral horizons k Accumulation of pedogenetic carbonates no restriction l* Capillary fringe mottling (gleying) *only in FAO no restriction n Pedogenetic accumulation of exchangeable sodium no restriction p Ploughing or other human disturbance no restriction E, B or C as Ap r* Strong reduction *only in FAO no restriction t Illuvial accumulation of silicate clay mineral horizons w Development of colour or structure B horizons z Pedogenic accumulation of salts more soluble than gypsum no restriction d Dense layer (physically root restrictive) x Fragipan characteristics no restriction Subordinate distinctions within master horizons full list FAO book page 72
  5. 5. Discontinuities In mineral soils, Arabic numerals are used as prefixes to indicate discontinuities. Numbering starts with the second layer of contrasting material, which is designated „2”. Underlying contrasting layers are numbered consecutively. Where two or more consecutive horizons formed in one kind of material, the same prefix number applies to all of the horizon designations in that material. In organic soils, discontinuities between different kinds of layers are not identified. A B 2C 3C 4C A B 2C 3Bt 3C
  6. 6. Suffix Short description Used for b Buried genetic horizon mineral horizons Ap C Ab C Used in mineral soils to indicate identifiable buried horizons with major genetic features that were formed before burial. If the buried horizon formed in a material lithological like that of the overlying deposit, a number prefix is not used.
  7. 7. Suffix Short description Used for b Buried genetic horizon mineral horizons Ap AB B 2Ab 2Blb 2Cl Used in mineral soils to indicate identifiable buried horizons with major genetic features that were formed before burial. If the material in which a horizon of a buried soil formed is lithological unlike that of the overlying material, the discontinuity is designated by number prefixes and the „b” symbol for a buried horizon is used as well.
  8. 8. Cr Suffix Short description Used for r* Strong reduction *only in FAO no restriction Cr
  9. 9. Gleyic colour pattern Stagnic colour pattern Gleization A E Btg C A Bl Cr
  10. 10. Suffix Short description Used for l* Capillary fringe mottling (gleying) *only in FAO no restriction Cl
  11. 11. Suffix Short description Used for g* Stagnic conditions / *USA strong gley no restriction Bg
  12. 12. Bc Suffix Short description Used for c Concretions or nodules mineral horizons
  13. 13. Bc
  14. 14. PAGE 79
  15. 15. RULES FOR CLASSIFICATION (three steps) The expression, thickness and depth of layers are checked against the requirements of WRB diagnostic categories, defined in terms of morphology and/or analytical criteria. (overlapping or coinciding possible) Step 1 – the diagnostics
  16. 16. RULES FOR CLASSIFICATION The combination of diagnostics compared with the WRB Key in order to find the RSG, which is the first level of WRB classification. The user should go through the Key systematically!!!! The soil belongs to the first RSG for which it meets all specified requirements. Step 2 – the key
  17. 17. RULES FOR CLASSIFICATION For the second level of WRB classification, qualifiers are used. Step 3 – the qualifiers Principal qualifiers: are regarded as being most significant for a further characterization of soils of the particular RSG. They are given in a ranked order. Supplementary qualifiers: All other qualifiers (further details about the soil). They are not ranked, but listed alphabetically.
  18. 18. Base Saturation Basic cations=∑ K+,Ca2+, Mg2+, Na+10 cmol (+)/kg Basic cations CEC Base saturation % = x 100 MEASURED IN 1 M NH4OAc (pH 7) WRB 2006
  19. 19. WRB2014/2015 Effective base saturation Exchangeable (Ca+ Mg + K + Na) Exchangeable (Ca + Mg+ K + Na)+ Al exchangeable bases by 1 M NH4OAc (pH 7), exchangeable Al by 1 M KCl (unbuffered)] of < 50%:
  20. 20. A E Bt C L A Y ARGIC ARGIC ARGIC ARGIC CEC / kg clay ≥ 24 cmol+ CEC / kg clay ≥ 24 cmol+ CEC / kg clay < 24 cmol+ CEC / kg clay < 24 cmol+ eB ≥ 50 % eB ≥ 50 % eB < 50 % eB < 50 % Luvisol Alisols Lixisols Acrisols In major part between 50-100 cm

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