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Cards (27)

  • What is the main control on the soil type?
    Controlled largely by the parent rock. It controls the colour, nutrients quality, ph of the soil and drainage properties.
  • The 4 things that make up soil
    • air
    • rocks/minerals
    • organic matter
    • water
  • The inputs of soil
    • gases from atmosphere
    • precipitation
    • nutrients from parent rock
    • organic matter from decay of organisms
  • Outputs of soil
    • soil erosion
    • evapourtranspiration
    • leaching of the soil
  • What system are soils?
    Soils are an open system.
  • Stage 1: Weathering
    • Weathering breaks apart the parent rock into pieces and forms the regolith
    • Clay particles join together (process of aggregation)
  • Stage 2 : Colonisation/humification
    • Once the rock has been broken apart, organisms such as algae/ lichens can start to colonise the area, and then add organic matter to the soil when they die.
  • Role of earthworms in the soil
    • break organic matter into smaller pieces
    • mix and aerate the soil
    • increase the soul pH
    • improve the soil stucture
  • What is the humification?
    Process by which dead organic matter is decomposed to form humus.
  • Chelation
    As the organic matter decomposes, it releases nutrients and organic acids, these acids attack clays releasing iron and aluminium
  • Stage 3 : Translocation
    • Movement of soil components in any form or in any direction
    • Occurs with greatest effect with either very high or very low rainfall.
    • Most common in tropical or desert climates
  • Leaching
    Common in areas of intense high rainfall.
    It is the carrying of elements in a dissolved form.
  • What is leaching controlled by?
    Solubility of an element
    The more soluble a mineral is the greater is suspectibilty to leaching
    Rainfall
    Leaching becomes more rapid as the percolating water becomes more acidic.
  • Parent rock material( factors affect formation of soil)
    Controls
    • soil colour, therefore temperature
    • mineral component
    • soil texture, which affects the drainage of the soil
    • soil depth
  • Climate( factors affect formation of soil)
    Climate affects the rate of weathering.
    In hot arid climates, high temperatures draw moisture up to the surface.
    This is called salinisation.
  • Topography( factors affect formation of soil)
    • Precipitation increases with altitude but temperatures decrease.
    • Valley floors have deeper soil due to soil creep downwards
    • A steep slope means, increased drainage, increased soil erosion, increases run off
  • Soil biota( factors affect formation of soil)
    Plants:
    Add organic matter when they die. Humic acid are released during decomposition and may break down the clays.
    Worms:
    mix and aerate the soil.
    Fungi/bacteria
    assist in decomposition and decay of dead vegetation which releases humic acids to the soil. The bacteria can also fix nitrogen and assist in nitrification of the soil.
  • Time( factors that affect formation of soil)
    The longer the soil has to form, the greater the weathering and organic matter breakdown; meaning deeper soils to support a higher species diversity
  • Soil organic matter practical (Step 1)
    • Use the dry sample of soil, place the crucible with soil onto the tripod and clay pipe triangle above the bunsen burner
  • Soil organic matter practical (Step 2)
    • Light bunsen burner and heat the sample, maintain a red glow on the crucible for 30 minutes
  • Soil organic matter practical (Step 3)
    • Allow to cool
  • Soil organic matter practical (Step 4)
    Measure the mass of the crucible with the burned soil
  • Soil organic matter practical (Step 5)
    Use the equation below to calculate soil organic content as a % of dry mass
    Soil organic content as % of dry mass= ( C - D ) / ( C -A ) X 100
  • Soil compaction practical (Step 1)
    • Hold the knitting needle perpendicular to the ground at a height of 1 metre and let go
  • Soil compaction practical (Step 2 )
    • Hold the knitting needle at the surface of the soil
  • Soil compaction practical (Step 3)
    • Pull out from the soil and measure the length of knitting needle ( mm ) that was in the soil