The impact of salinity on greenhouse grown crops, especially when grown in substrate systems, differs from the impact of salinity on crops grown under field conditions. The most striking difference between greenhouse and field conditions is the overall much higher concentrations of nutrients in greenhouse soils and substrates. This especially holds where high ion levels are knowingly maintained in the soil or substrate solution to control plant growth under poor light conditions or to improve quality of the produce (Sonneveld, 2000). Thus, in greenhouse cultivation nutrients contribute substantially to the osmotic potential of the solution in the root environment. This especially is the case in substrate systems when water of a low salinity status is used and thus, the osmotic potential is more or less solely brought about by nutrients. Furthermore, factors strongly affecting salinity effects on crops, like the climatic conditions in the greenhouse and the addition of water, are artificially controlled and therefore, differ much from those under field conditions. On thing and another induce special requirements on the management of salinity under greenhouse conditions.