Plants, Nutrients and Australian Soils

The smallest soil particles determine the chemical characteristics of a soil.

The most important particles are the fine clay minerals (0.2 - 1 μm), which have a relatively large surface area per unit volume. Kaolinite is a common clay mineral.

The surface area of clay particles may be up to 800 m/g (i.e. several orders of magnitude greater than for sands or silts). They generally carry a negative surface charge and thus can bind both water and various important cations (e.g. NH4+, Ca2+, Mg2+, K+).

In addition to the mineral component of soil, organic matter, called humus, is also a source of chemical nutrients for plants.

Kaolinite is a common clay mineral composed of compound layers of ions (silicon, hydroxyl and aluminium ions). The different layers are held together by hydrogen bonding.