Please enable JavaScript.

Coggle requires JavaScript to display documents.

SOILS :tada:, image, image, Screenshot 2021-02-22 at 11.07.37, Screenshot…

- - - - Organisms
        
        Conifers
        
        Needles difficult to break down
        
        Soil organisms discouraged
        
        Organic Material builds up
        
        Humus tends to be ‘mor’ type
        
        Acidification of soils
        
        Needle chemicals - leaching
        
        Conifers take little Ca up from the soil but lock it in timber
        
        further encourages leaching
        
        Earthworms
      - Relief – Hydrology (slopes)
        
        The position of a soil on a slope greatly affects its drainage status
        
        Soils situated close to water (rivers, lochs, etc.) will tend to be wet (soil pit 5)
        
        Mid-slope soils tend to be better drained (soil pit 2)
      - Time – Dunes
      - Parent Material – Rendzina
        
        Associated mainly with calcareous grasslands
        
        High OM content
        
        Very freely drained
        
        Shallow soils
        
        Very rare in Scotland
        
        Formed on chalk or LMST
      - Climate - Peat Formation
        
        Low lying Peats
        
        Fen peats
        
        Basin peats
        
        Climatic peats
        
        Ombrotrophic peats
        
        Raised Bog
        
        Blanket peats
- - - - remains in situ
      - chemical weathering
        
        Solution dissolving salts e.g. Limestone
        
        Oxidation addition of oxygen
        
        Hydrolysis
      - physical weathering
        
        Frost shattering (freeze/thaw)
        
        Wetting drying
        
        Hot/cold (diurnal fluctuations in temperature)
        
        Aggregation (structure formation)
  - - - causes ANAEROBIC conditions
    - - REDUCTION
  - - - binding together
  - - - Freely drained
      - Sandy
      - Leached
      - Acidic
    - - The acidity dissolves iron and aluminium
        
        Eluviation (E horizon)
        Material has exited an horizon
      - Distinctive pale E horizon, due to eluviation of iron (Fe) and aluminium (Al) oxides out of the upper horizon
      - Fe and Al are subsequently deposited (illuviated) in the orange B horizon, and may accumulate to form a hard iron pan
        
        Illuviation (Bs horizon)
        Material has gone INTO an horizon from above
- - - - Clay < 0.002 mm
      - Silt 0.06mm - 0.002 mm
      - Sand between 2.0mm and 0.06 mm
      - Texture is the sand %, silt % and clay % in the soil. This refers only to the fine earth fraction, less than 2mm
      - Stones > 2 mm
  - - - Humus is an important ‘glue’
      - Clay particles also help
      - Calcium helps to bind the particles too
      - These ‘secondary’ units are called structures, peds or aggregates
  - - - Different stages of decomposition
      - Fresh leaves, recently dead animals
      - Some decomposition, identifiable leaves etc
      - Humus – very decomposed, no parts identifiable
        
        Humus can also describe the type of OM in soil:
        
        Mor humus (LFH)
        
        lies on top of the ‘mineral horizons (that are dominated by sand, silt and clay) and is an ‘O’ horizon.
        
        Mull humus
        
        imuch more intimately integrated (you can’t easily differentaite the mineral matter from the OM) and does not lie on top of the mineral horizons. This is an ‘A’ horizon.
        
        Moder humus
    - - Decrease in OM :heavy_minus_sign:
        
        – decomposition, lack of additions, ploughing
      - Increase in OM :heavy_plus_sign:
        
        … addition of OM (from leaves, FYM etc.) is greater than loss (e.g. through decomposition)
        
        Decomposition is affected by microbial activity. The following conditions slow down or inhibit this process:
        
        Low temperatures
        
        Low oxygen levels (caused by waterlogging and or compaction. Ploughing is a major factor which decreases OM. Why?)
        
        Acidity
        
        Lack of decomposition results in OM accumulation = higher OM levels
        
        Waterlogged soils (e.g. peats and gleys) lack of oxygen inhibits decomposition
        Also acid soils inhibit decomp (e.g. podzols)
- - - - Oxidation and aggregation