LEACHING IRRIGATION TO PREVENT SALT ACCUMULATION IN THE SUBSTRATE

     In order to prevent salt accumulation in the substrate, the adoption of high leaching fraction (LF) is quite common in soilless culture, in particular when brackish water is used for the preparation of nutrient solution. However, some problems related to environmental and economical aspects indicate the necessity to reduce LF and hence the loss of nutrients. For this purpose, maintaining a low LF, water without added nutrients could be used to leach the salts in the substrate. In this work, the effects of additional daily leaching irrigation made with different volumes of water (0, 95, 220, 470 g plant^-1d^-1) were studied on tomato grown on expanded clay and fertirrigated using a LF of about 6 %. The yield and the above ground biomass increased in comparison to the control when a water volume of at least 220 g plant^-1d^-1 was adopted. This increment was coupled to an increase in fruit fresh weight and a reduction of fruit titratable acidity, soluble solids and dry matter percentage. Therefore, when low LF is adopted to reduce the negative effects on the environment, salt accumulation may be prevented by a daily leaching irrigation of substrate using volumes of water equal to or more than 220 g plant^-1d^-1.

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