Glossary of soil terms

Some important terms that define soil include:

• aeolian - matter transported by wind
  
• aerobic soils - soils where oxygen is available, found in well-drained soils
  
• alluvial - matter transported by water
  
• anaerobic soils - oxygen deficient soil, generally found in conditions where soil is waterlogged or poorly drained, and water has replace soil air
  
• colluvial - refers to material transported by gravity
  
• fertility - capacity of soil to provide nutrients for plant growth. Includes:
  • chemical -supply of nutrients
  • biological - population of micro-orgs and organic matter being broken down by them 
  • physical -soil structure neccessary for water and nutrient storage
• horizon - layers of soil, with properties distinct from those above and/or below
  
• massive - lack of horizons. i.e. soil as a solid mass 
  
• parent material - can include bedrock, alluvium or wind blown deposits
  
• permeability - governs the rate at which water moves through a soil. Sands and gravels have very high permeability, heavy clays very low.
  
• porosity - degree to which the soil has pores or cavities, i.e. % of soil unoccupied by solid particles. (There can be small or large pores, many or few.)
  
• structure - How the particles group together to form 'peds'. For example, a beach soil does not cling at all and so is structureless, while in a massive earth the particles join in a large featureless mass. Most soils are somewhere between the two. An indicator of soils capacity to allow air and water into and out of the soil profile.
  
• texture - indicates size of soil particles, from clay which is the smallest up to sand and then gravel. Can indicate water holding capacity, ploughability and fertility.
  
• water-holding capacity - the amount of water held by soil once excess has drained away. Important for plant growth.