Soil formation is controlled by five factors :
- nature of parent rock,
- the topography,
- the climate,
- the organism in the soil and
- time.
1. Parent Rock: The original rock called parent rock, from which the soil is formed, determines its basic characteristics. For example, shales contribute clays, while sandstones contribute sand grains.
2. Climate: Temperature and precipitation are the main climatic factors affecting soil formation. Frequent temperature changes and presence of water quicken soil formation through increased weathering.
3. Topography: Topography affects the drainage of an area. On a steep slope, there is hardly any chance of accumulation of weathered rocks. They are moved down the slope by water and under force of gravity. In plains and areas with gentle slope, soils are accumulated without any hindrance.
4. Organisms: Dead plants and animals provide humus to soil. Organisms like earthworms and ants through their movements create space for air and water in the soil.
5. Time: Time factor is also important because longer the time for soil formation, more deeper is the soil layer. Besides weathering of rocks, soil is also formed by deposition of materials by moving waters (rivers) and winds in low-lying areas. Alluvial soils of river valleys are very fertile and deep.
