Soils form through a complex process known as pedogenesis, which is influenced by various factors including climate, parent material, topography, organisms, and time. These factors interact to create the diverse array of soils we find around the world.
- Parent Material: Soil formation begins with the weathering of parent material, which can be rock, sediment, or organic material. Mechanical and chemical weathering processes break down these materials into smaller particles. Soils often have characteristic chemical and physical properties that related directly to the nature of the parent material from which they are formed.
- Climate: Temperature and precipitation affect the rate of weathering, the leaching of minerals, and the decomposition of organic matter. In tropical regions, soil formation is faster due to higher temperature and moisture levels which increase biological activity.
- Topography: Steeper slopes usually experience more erosion which significantly affects soil profile development by removing the upper horizons, especially the nutrient-rich topsoil (A horizon). This can lead to soil profile shallowing, reduced organic matter, disrupted nutrient cycling, and impact the orderly development of soil horizons, soil fertility and structure.
- Organisms: Soil organisms, such as earthworms, bacteria, and fungi, break down organic matter and help mix soil layers. Plant roots also contribute to soil structure and nutrient cycling.
- Time: Soil formation is a slow process that can take decades, centuries or even longer. Soils tend to become more developed and layered over time, with distinct horizons like topsoil (A horizon) and subsoil (B horizon). Complex interactions of all the above factors can affect the rate and outcomes of soil development. Erosion can even completely reset the clock on soil development by removing the whole soil profile creating mosaics of soils of different ages.
Reference: Brady, N.C. and Weil, R.R. (2008) The nature and properties of soil, 14 ed. Prentice-Hall, Upper Saddle River, New Jersey.
