Lecture 10.pptx king of kotha koojhtggggggv

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1. Soil Taxonomy – Structure – D ifferentiating characters and limitations – Formative element Lecture: 10 1 Dr. M. Vijayakumar, Ph.D., Assistant Professor (SS&AC) AC&RI, Kudumiyanmalai [email protected]

2. Taxonomy - Science of classification Soil taxonomy - System of soil classification Differentiating characters: Grouping of soils based on soil properties Based on soil temperature and moisture regimes Soil Taxonomy 2

3. Essentiality of name? Name used in Genetic system are biased in favour of Colour (brown, red or grey) Vegetation (prairie, grass or forest) a nd shows no relationship with each other In view of these limitations nomenclature used in Soil Taxonomy is different and based on Greek or Latin languages Nomenclature 3

4. Basic principles followed in coining names, (according to Heller (1963) Should be most easily remembered Should suggests some properties of the object Should suggests the place of a taxon in the system Should be as short as possible Should be as euphonic as possible Should fit readily in as many languages as possible Nomenclature 4

5. Example Aridisols (L. aridus – dry ; solum – soil) – soils of dry places Vertisols (L. verto – turn ; solum – soil) – soils which churn or invert Nomenclature 5

6. Structure of Soil taxonomy Higher categories Order - the highest category in the, system Suborder - comparable to great soil groups of the genetic system Great group - A basic category, based on diagnostic subsurface horizons Lower categories Subgroup - a new category designed to define the central concepts of great groups Family - a practical category for making predictions and land use plans. Series - the lowest and the most specific category 6 Hierarchy of Soil taxonomy

7. Sl. No. Category Differentiating characteristics and description 1. Order (12) There are 12 orders ( AVAGAMI HOUSE ). A ridisol , V ertisol , A lfisol , G elisol , A ndisol , M ollisol , I nceptisol , H istosol , O xisol , U itisol , S podosol , and E ntisol . These are based largely on morphology , as produced by soil forming processes and indicated by the presence or absence of major diagnostic horizons . 2. Suborder (63) It emphasizes genetic homogenity , wetness (SMR) , climatic environment, parent material and vegetation effects. 3. Great Group (240+) The major emphasis is on the diagnostic horizons ( except in Entisols which have no such horizon) and presence or absence of diagnostic layers ( plinthite , fragipan , duripan ), base status, SMR and STR Differentiating characteristics of different categories in Soil taxonomy

8. S. No. Category Differentiating characteristics and description 4. Subgroup (1000+) The Typic is used to define the central concept of a great group 5. Family The soil properties that are most important for plant growth (like texture, solum , mineralogical, class , soil temperature class and pH are used to differentiate families; practical prediction for land use planning 6. Series (200+ in India) It is the lowest category in the system. The series is a collection of soil individuals, essentially uniform in differentiating characteristics (like colour, texture, structure, consistency, pH and EC ) and in arrangement of horizons. The series are named after the geographic name of the place where it was first recognized. 7. Soil phase Based on differences in surface soil texture, solum thickness; percentage slope, the stoniness, the saltiness, the extent of erosion damage and other conditions. Differentiating characteristics of different categories in Soil taxonomy

9. Name of order Formative element Derivation of formative element Mnemonicon or memory device Soils equivalent in other systems Alf isol alf Meaningless syllable Pedalfer Grey-brown Podzolic ; Non-calcic brown soils; Degraded chernozems And isol and Jap. and Ando Volcanic ash soils Ar id isol id L. aridus ; dry Arid Sierozem , Solonchak, Desert, Brown and reddish brown Ent isol ent Meaningless Syllable Recent Azonal , low-humic Gley soils H ist osol ist Gr. histos , tissue Histology Bog soils Inc ept isol ept L. inception , beginning Inception Ando, Sol Brun Acide , Forest and Humic Gley soils 9 Formative elements of soil order and their derivation

10. Name of order Formative element Derivation of formative element Mnemonicon or memory device Soils equivalent in other systems M oll isol oll L. mollis , soft Mollify Chesnut , Chernozem, Brunizem (prairie), Rendzinas Ox isol ox French oxide Oxide Laterite soils , Latosols Sp od osol od Gk. spodos , wood ash Podzol, odd Podzol , Brown Podzolic & Ground water podzols Ult isol ult L. ultimus , Last Ultimate Red-yellow Podzolic ; Hal-bog soils; Grey wooded& associated planosols V ert isol ert L. verto , turn Invert Grumosols , Black cotton soils ( Regur ) G el isol el L. gel , very cold or ice Frost churnin;g Gelid Frozen Thundra soils, showing Cryoturbation Formative elements of soil order and their derivation

11. 11 SOIL MOISTURE and SOIL TEMPERATURE REGIMES Each soil has a specific environment under which it has developed Soil Moisture and Temperature Regimes control and guide soil utilization for plant growth

12. 12 SOIL MOISTURE REGIMES Soil Moisture Regime (SMR) refers to the presence or absence of water in a soil at different times of a year. Soils considered moisture when it is at moisture tension less than 1500 kPa and dry when the tension is >1500 kPa with in Soil Moisture Control Section (SMCS). The limits of SMCS are determined by soil depth to which the soil at PWP is moistened when 2.5 cm and 7.5 cm of water are added at the surface. In general, upper and lower limits of SMCS in loamy soils are at 20 cm and 60 cm , respectively

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14. 14 SOIL MOISTURE REGIMES When salt concentration reaches the level that limits moisture availability to plants, is considered to be Physiologically dry . SMR is a partial function of climate, soil and landform. SMR defined in terms of no. of days the SMCS remain moist with moisture tension b/w 33 kPa and 1500 kPa (FC-PWP). The SMCS defined as the depth limits of soil that regulate the moisture supply , and this depends on its texture.

15. 15 SOIL MOISTURE REGIMES Besides controlling crop growth, SMR important for Pedogenesis Nutrient availability Classification of soil at different categorical levels such as Soil Family, Suborder and occasionally at Order level (As in Aridisols )

16. 16 SOIL MOISTURE REGIMES In nature, there exist three dominant SMR: Saturated – Taxonomically as AQUIC (Anaerobic condition, its not conducive to normal growth) Non-leaching – Taxonomically as ARIDIC (water moves into SMCS for a very short period in a year, reasons PET) Leaching – Taxonomically as UDIC (water moves into soil almost throughout year, if not frozen) In b/w leaching and non-leaching environment, there exist partially leaching SMR are ‘ Ustic (summer monsoon rain as in India) ” and ‘ Xeric (winter rains as in Mediterranean region) ’

17. 17 As a thumb rule, any month with an average precipitation of more than 50 mm is considered to keep the SMCS partially moist

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19. 19 SOIL TEMPERATURE REGIMES Soil temperature regimes are based on mean annual soil temperatures.  Soil temperatures are taken at a depth of 50 cm from the soil surface, using the Celsius (centigrade) scale.    No biotic activity at below freezing point (0 o C ) Root growth and seed germination of most plants impossible (0 to 5 o C ) “biologically inactive” and most of mesophytic plants affected (> 35 o C ) These regimes greatly affect the use and management of soils, particularly for the selection of adapted plants. 

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21. 21 The Mean Annual Soil Temperature (MAST) can be computed from Mean Annual Air Temperature (MAAT) by adding, 3.5 o C to the mean air temperature for areas situated b/w 8 o and 16 o N latitude. 2.0 o C to the mean air temperature for areas situated b/w 16 o and 26 o N latitude. 1.5 o C to the mean air temperature for areas situated b/w 26 o and 33 o N latitude .

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24. Application Differentiating characteristics criteria 24

25. Criticism of Soil Taxonomy 25

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27. 27 1 . Partially leaching soil moisture regime   A) Aquic, udic B) Ustic , xeric   C) Aridic, xeric D) Udic, aquic 2 . The lower categories are defined by ------------ number of differentiating characters   A) Few B) Medium   C) More D) Minimum 3 . Grumosol soil belongs to which order   A) Alfisol B) Andisol   C) Vertisol D) Aridisol 4 . Inceptisols are representated by the formative element   A) ept B) and   C) alf D) oll 5 . The term “biologically inactive” will be used when temperature falls between -------------   A) 10 to 15 o C B) <0 o C   C) 15 to 25 o C D) 0 to 5 o C