Irrigation water quality for greenhouse horticulture

Water, in terms of both quantity and quality, is crucial to the success of horticulture greenhouse production. As water supplies are often limited, it is necessary to use low quality water for irrigation purposes. This is particularly true in Mediterranean countries, where growers increasingly face problems associated with low quality water. In this chapter the most important water physical and chemical quality parameters are discussed. These include pH, alkalinity and salinity. Furthermore, a review of the criteria for water quality assessment is presented. Water tests to be conducted prior to selecting a greenhouse site are also briefly described with reference to the official methods of water analysis. The presence of high soluble salts in irrigation water is one of the most limiting factors in greenhouse crop production. As an alternative to using seawater – a common practice in some Mediterranean areas (e.g. Almería, Spain) – wastewater from industrial processes or lower grade water from wells contaminated by seawater infiltrations can be used. Management and agronomic techniques that may be used to combat some of the problems associated with the use of these “waters” are discussed, including methods to correct poor quality irrigation water.