Soil

• Constituents of soil


  • Inorganic (mineral) matter
  • Organic matter
  • Gases or water
  • Organisms-biota
• Inorganic (mineral) matter


  Derived from weathered rock or sediment (the parent material), provides the physical bulk of most soils, weathered minerals release important nutrients for plants, this process occurs rapidly in tropical regions due to high temperatures and rainfall
• Organic matter


  Rotted (decomposed) vegetation that adds bulk and cohesion to the loose rock material, provides important nutrients for plant growth, helps to retain moisture in the soil
• Gases or water


  Soil contains air pockets which are important for soil formation and maintaining healthy plant growth
• Organisms-biota


  Such as earthworms are very important in soil formation, especially in the decomposition of dead vegetation, fungi and bacteria are also important in mixing the soil and drawing down nutrients
• Latosols


  • Deep soils that typically form in tropical rainforest environments
  • Characterised by being red in colour due to high concentrations of iron and aluminum
  • Generally not very fertile
• Warm and wet climate

  • Causes rapid chemical weathering of the parent material, accounting for the great depth of the soil
  • High rainfall leads to water draining through the soil, dissolving minerals such as iron and redepositing them further down (leaching), accounting for the low levels of fertility and the reddish colour of the lower soil horizons
  • Promotes decomposition as fungi and bacteria thrive in these conditions
• Lush rainforest vegetation


  Provides plenty of dead organic matter to be decomposed, although this adds large quantities of nutrients to the soil, the plants quickly absorb them and leave the soil impoverished and relatively infertile
• Warm and moist soil conditions

  Many organisms thrive, helping to mix up the nutrients and making them available to the plants, ideal for decomposers such as fungi and bacteria which release nutrients from rotting vegetation
• Water draining rapidly through soils

  Dissolves and carries away nutrients (leaching), causing the soils to be relatively infertile