ABSTRACT
The soil acts as a reservoir for water, making it available for plants as needed. Soil water is the most limiting factor for crop production. The plant available moisture storage capacity of a soil provides a buffer, which determines a plant's capacity to withstand dry spells. Water held in soil is gravitational and capillary water. The degree to which water clings to the soil is the most important soil water characteristic to a growing plant. Field capacity (FC) approximates the amount of water held in soil after it has been fully wetted and all gravitational water been drained away. Water lost to atmosphere is by evaporation, transpiration, and evapotranspiration (ET). The removal of excess water either from the ground surface or from the root zone is called drainage. Soils allowing water to enter and drain from the profile at rates suited to the selected land use are ideal. The economics of ameliorating soil drainage depends on the individual situation, soil type, severity of compaction, land use, and the management options available. A balance is required between increased drainage, and the wish to retain as much water as possible within the profile for use by crops or pastures.
