Soil

Soil system

A soil system is a dynamic system composed of organic and inorganic matter, water, air, and living organisms that support terrestrial life by providing nutrients, water, and a medium for plant growth.

Soil Profile

The soil develops a stable, layered structure known as a profile. The soil profile consists of several horizons, produced by interactions within the system over long periods.

Horizons:

• O Horizon: Organic matter like decomposed leaves and plant material.
• A Horizon (Topsoil): Rich in organic matter, nutrients, and biological activity.
• B Horizon (Subsoil): Contains minerals leached from the upper layers and less organic material.
• C Horizon: Partially weathered parent material.
• R Horizon: Unweathered bedrock (parent material).

Inorganic and Organic Components of the Soil System

1. Inorganic Components:
   • Minerals like sand, silt, and clay are derived from weathered rocks.
   • Essential nutrients like nitrogen, phosphorus, and potassium.
2. Organic Components:
   • Humus: Decomposed organic matter that retains nutrients and moisture.
   • Living organisms: Microorganisms (e.g., bacteria, fungi) and macroorganisms (e.g., earthworms, insects).

Inputs and Outputs of Soil

• Inputs:
  • Dead organic matter (e.g., plant and animal residues).
  • Mineral particles from weathering.
  • Water and atmospheric gases.
• Outputs:
  • Nutrients removed by plants and erosion.
  • Leaching: Loss of soluble nutrients to deeper soil layers or groundwater.

Transfers and Transformations in the Soil System

• Transfers:
  • Movement of nutrients, water, and organisms between soil layers.
  • Erosion and deposition by wind or water.
• Transformations:
  • Decomposition: Organic matter broken down by microorganisms.