IB Environmental systems and societies 5.1A Soil System Key Definitions

Aeration is the exchange of gases between soil and the atmosphere.

Decomposition is the breakdown of organic nitrogen in dead organisms and waste products into ammonium (NH₄⁺).

Denitrification is the conversion of nitrates (NO₃⁻) back into nitrogen gas (N₂), which is released into the atmosphere.

Erosion is the removal of soil particles by wind or water.

Humus is a dark, crumbly substance that retains waterand nutrients, improving soil fertility.

Infiltration is the process by which water enters the soil from the surface.

Leaching is the downward movement of dissolved minerals and nutrients through the soil.

Nitrification is the conversion of ammonia (NH₃) to nitrates (NO₃⁻).

Nutrient cycling is the movement of nutrients like nitrogen, phosphorus, and carbon through the soil, plants, and atmosphere.

Percolation is the downward movement of water through soil layers.

Soil is a dynamic system that interacts with the atmosphere, hydrosphere, biosphere, and lithosphere.

A soil profile is a vertical section of soil that reveals distinct horizons, each formed by long-term interactions of organic and inorganic materials.

Weathering is the process of breaking down rocks and minerals into smaller particles, forming the inorganic component of soil.