5.1 Introduction to soil systems

Soil composition

Made of air, water, organic matter (humus) and mineral particles (silt, clay, chalk, sand etc.)

Parent material

The general physical, chemical, and mineralogical composition of the unconsolidated material, mineral or organic, in which soil forms through erosion or other means of weathering.

Humus

Plant and animal matter in the process of decomposition

Translocation

The sorting of layers of soil due to the movement of water-carrying particles through the soil.

Salinization

The deposition of salts from freshwater due to constant watering

Leaching

When water flows down into the soil, dissolving minerals and transporting them downwards.

Humus

Plant and animal matter in the process of decomposition

Horizons

Horizontal layer of soil defined by distinctive physical features

O horizon

Uppermost layer of soil conposed of newly added organic material with detrivores decomposing dead organic matter

A horizon

Below O horizon where humus is mainly formed and mixed with mineral layers. Can form peat soils in waterlogged conditions q

E horizon

Where leeching occurs of metals and organic matter

B horizon

Where minerals and organic matter gets deposited. Typically clay and salts.

C horizon

Weathered rock from which the soil forms

R horizon

No soil and made of parent material

Porosity

The amount of space between particles

Permeability

The ease with which gases and liquids can pass through the soil.

• Sandy soil drain well while clay heavy soils retain water well due to particle sizes

  • Sand biggest, silt middle, clay smallest

Rate of soil formation

Takes a very long time at 1 ton per hectare a year.

• Fertile soil is an extremely limited resource due to how long it takes to form

• Various anthropocentric causes destroying microbes in soil, thus killing the soils fertility