1. Mineral Matter:
* Sand: Coarse particles, gritty to the touch, contribute to drainage and aeration.
* Silt: Medium-sized particles, feel smooth like flour, retain water better than sand.
* Clay: Fine particles, sticky and smooth when wet, hold water and nutrients.
2. Organic Matter:
* Humus: Decomposed plant and animal remains, dark and rich in nutrients, improves soil structure and water retention.
* Roots: Living plant roots contribute to soil aeration and structure.
* Microorganisms: Bacteria, fungi, and other organisms break down organic matter and release nutrients.
3. Other Components:
* Water: Essential for plant growth and microbial activity.
* Air: Required for root respiration and other biological processes.
* Nutrients: Released from decomposing organic matter and available to plants.
Key Characteristics of the A Horizon:
* Darker color: Due to the presence of humus.
* Loose and friable texture: Facilitates root growth and aeration.
* Rich in nutrients: Supports plant growth.
* High biological activity: Supports a diverse range of microorganisms.
Note: The specific composition of the A horizon varies depending on factors such as climate, vegetation, and parent material.
