1. Parent Material: This is the bedrock that the soil is derived from. It can be igneous, sedimentary, or metamorphic rock, each contributing different minerals to the soil.
2. Weathering Products: As the parent material breaks down through weathering processes (physical, chemical, and biological), it releases minerals into the soil. Common minerals include:
* Sand: Larger particles, primarily quartz, but also feldspars, mica, and others.
* Silt: Medium-sized particles, including clay minerals like illite and kaolinite.
* Clay: The smallest particles, often composed of complex clay minerals like smectite, vermiculite, and chlorite.
3. Other Inorganic Components:
* Iron oxides: Responsible for the red, orange, and yellow colors in some soils.
* Calcium carbonate: Can form from the weathering of limestone and contribute to soil pH.
* Humus: While technically organic, it has strong binding properties with minerals, influencing soil structure and nutrient availability.
The Importance of the Inorganic Fraction:
* Structure: The size and arrangement of mineral particles influence soil texture, porosity, and water-holding capacity.
* Nutrient Supply: Minerals provide essential nutrients like nitrogen, phosphorus, potassium, and calcium.
* Water Retention: Clay minerals have a strong affinity for water, helping to retain moisture.
* pH: The type of minerals present can influence soil pH, affecting plant growth.
The proportion of each component in the inorganic fraction varies greatly depending on factors like climate, parent material, and time.
It's important to note that the inorganic and organic components of soil work together to create a dynamic ecosystem.
