Manual of Soil Properties and Land Preparation

 Introduction to Soil Formation

Soil is a natural body consisting of layers (soil horizons) that are composed of weathered mineral materials, organic matter, air, and water. Soil formation is a slow process governed by five main factors:

Parent Material: The raw geologic material (usually rock or organic deposits) from which the soil is formed.

Climate: Temperature and moisture levels that affect the speed of chemical reactions and biological activity.

Topography: The slope and "lay of the land" which affects drainage and erosion.

Biological Factors: Plants, animals, and microorganisms that add organic matter.

Time: The duration over which the other four factors have been interacting.