INFLUENCE OF NACL SALINITY STRESS ON YIELD, PLANT WATER UPTAKE AND DRAINAGE WATER OF TOMATO GROWN IN SOILLESS CULTURE

On the one hand, in a closed soilless system, the use of saline water is usually avoided due to the risk of salt build up problems in the substrate; on the other hand, in an open soilless system, excess volumes of nutrient solution with Leaching Fraction (LF) 40–50% are usually applied to prevent salt accumulation and this results in negative impact on the environment which today is not acceptable. Therefore, it is inevitable especially for the Mediterranean region where water resources are limited, to determine the proper LF related to salinity levels and plant growth stages. For this reason, we investigated the correlations between five concentrations of sodium chloride (The corresponding EC levels were 3, 4, 5, 6 and 7 dS m^-1) and tomato yield and quality, LF, plant water uptake and water use efficiency under greenhouse conditions using an open soilless system. In addition to yield reduction, total water supplied and LF were increased, while plant water uptake (measured as the differences between volume of nutrient solution supplied and LF) was reduced with increasing salinity. Water use efficiency (fruit yield L^-1) was not significantly affected by increasing salinity. Minimum LF ranged from 8.5 to 32.2% of the supplied water and strongly dependent on salinity level. This quantity was less than those usually applied in open soilless system and should receive more attention to minimize the negative environmental impact.