Hydrolysis

A chemical weathering process by which water dissolves minerals releasing nutrients which can be taken up by plants from the soil solution. The process can be considered as taking place over a couple of stages, with the initial stage being that of water entering the soil and then working its way through the soil profile. During this stage the water makes initial contact with soil minerals which contain ions, primarily cations. With the presence of water now being in contact with the soil minerals the next stage is that of the water molecules breaking the bond between the different chemical

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  Hydrophobic

A material which repels water. Soils can become hydrophobic due to waxy coatings on the soil particles, which mainly arises from the decomposition of organic matter and fungal activity. Dry patch is a disorder of some turf surfaces which is caused by the affected area being hydrophobic, with the application of wetting agents helping to reduce the repellent nature of the soil.

  Hygroscopic Water

Water that has been absorbed from a humid atmosphere and which is held very tightly onto soil particles by adhesion, and which is not generally available for use by a plant. If a soil has dried and / or a plant has used all available water and this is the only water remaining within a soil then unless water is readily made available to a plant, or it is able to become effectively dormant whilst the dry conditions persist, then it will have reached permanent wilting point and will die.

  Illite

A 2:1 layer clay mineral. Silicates, such as feldspar, is weathered to form this clay mineral, with alkaline pH and high concentrations of potassium and aluminium being typical outcomes.

  Illuvial Horizon

The B Horizon in a soil profile. It is where material from the A Horizon has been removed and accumulated in the lower layer of the B Horizon.

  Infiltration

The ability of water to move into a soil surface.

  Infiltration Capacity

The maximum rate, typically measured in millimetres per hour, that water can enter a soil. Also referred to as infiltration rate.

  Interceptor Drain

See Drainage Trench.

  Kaolinite

A 1:1 layer clay mineral. This can form following the weathering of feldspars under acid conditions, or by hydrothermal alteration.

  L Horizon/Layer/Zone

The Litter horizon within a soil profile. Where present, it forms part of the O Horizon.