Soils vary widely in composition and structure from place to place. Soils are formed through weathering of minerals and organic matter. Weathering is the action of wind, rain, ice, sunlight and biological processes, which breaks parent material down into smaller particles and alters their chemistry. Soils form from weathering in place although many soils are comprised entirely of transported weathered material which arrives as flood sediments, eolian deposits, or dust fall. The proportions and types of minerals and organic matter help determine the characteristics of a particular soil.

  1. Composition — Soil composed from solid, liquid and gas phases. Water and soil atmosphere are thus integral components of soils.
  2. Soil texture — refers to soil grain size. According to U.S. system grades defined as follows: sand — 2 to 0.02 or 0.05 mm; silt — 0.02 or 0.05 to 0.002 mm; clay <0.002 mm.
  3. Soil structure – the arrangement of soil particles into aggregates, which may have various shapes, sizes and degrees of development or expression.
  4. Soil color — Soil color often indicates soil moisture status and is used for determining hydric soils. Often described by using general terms, such as dark brown, yellowish brown, etc.
  5. Soil chemistry — A complex subject within soil science; some characteristics are: Soil pH, Cation, and Reduction and oxidation (Redox).
  6. The soil profile — A vertical cut that exposes soil layering or soil horizons. Horizons are formed by combined biological, chemical and physical alterations.
  7. Permeability — The ability of a soil to transmit water or air.
  8. Drainage — The rate in which water is removed from a soil.
  9. Soil biology — Soils serve as habitats for soil organisms varying in size from microorganisms to small animals.
  10. Soil smell — earthy odors are normally the product of microbial activity.
  11. Soil tilth — Where soil mineral particles are both separated and bridged by organic matter breakdown products, and soil biota exudates, it makes the soil easy to work.