Disease control in soilless systems

Irrigation water is often a source for the dispersal of soil-borne diseases all over the nursery. A systematic approach to water treatment can minimize the spread. Treatment may be executed at the moment the irrigation water enters the nursery, but it should certainly be treated if water is reused. Reuse of supply water is useful for a number of reasons. First there are savings of costs for the grower on water and fertilizers. Secondly a more stable environment of beneficial micro-organisms may develop around the roots, which may form a barrier against pathogens. Third, fewer fertilizers and remnants of crop protection products are leached to the environment resulting in a better ecological condition of ground- and surface water as prescribed by the EU Water Frame Work Directive. A number of water treatment methods can be used to eliminate pathogens out of the water. Heat treatment, UV-C radiation, slow sand filtration are a few to be mentioned here. These and others will be discussed technically and phytopathologically. Additional other control aspects will be discussed which may lead to a more efficient use of water, fertilizers and crop protection products. 99