Glossary Terms

Soil fertility

The ability of the soil to supply essential plant nutrients and soil water in adequate amounts and proportions for plant growth and reproduction in the absence of toxic substances which may inhibit plant growth.

Wilting point

Soil moisture content where the rate of absorption of water by plant roots is too slow to maintain plant turgidity and permanent wilting occurs. The average moisture tension at the outside surface of the moisture film around soil particles when permanent wilting occurs is 1500 kPa.

Water table

The upper surface of groundwater or that level in the ground where the water is at atmospheric pressure. Different horizons can be recognized, such as the highest and lowest average height of the groundwater level in summer or winter.

Water holding capacity

The capacity of soils to hold water that is available for use by most plants. It is commonly defined as the difference between the amount of soil water at field moisture capacity and the amount at wilting point. It is commonly expressed as mm of water per m of soil.

Water deficit

Amount of water (mm) needed to return moisture conditions of a soil back to field capacity.

Vadose zone

The aerated region of soil above the groundwater table. The unsaturated zone is characterized by a downward movement of leachate.


The capacity of soil to carry machinery without significant damage to the soil or the vegetation growing on it.

Surface water

Water bodies flowing over or resting on the surface of a land mass, natural waterway (rivers, streams, brooks and lakes) or artificial waterway, including irrigation, industrial and navigation canals, drainage systems and artificial reservoirs.

Surface irrigation

Application of water to the field that flows over the land surface or in narrow channels (e.g.furrow or basin sprinkler).

Sprinkler irrigation

Application of water to the field by a sprinkler system which mimics a high intensity rainfall, can be mobile of fixed.