GREEN SALAD PRODUCTION IN SOILLESS CULTURE UNDER SALINE IRRIGATION PRACTICE

Abstract

This study was carried out under protected conditions, using soilless culture inert substrates: Pozzolana (PZ), Gravel (GR) and Perlite (PR) to evaluate the possibility of using saline water as an irrigation source for producing the green salad lettuce variety 'Delia' (winter variety), and endive variety 'St. Levrent Midori' (spring variety). Mean daily water consumption (L m -2 day -1 ) varied with crop variety and substrates; higher values were found for plants grown on PZ (1.2 and 4.4) than those for plants grown on GR (0.6 and 2.3) and PR (0.8 and 3.5) for lettuce and endive varieties, respectively. The pH of drained nutrient solution was with an average value of 7.9 for lettuce and 8.5 for endive, while the EC-values were around 4.0 for lettuce and 4.5 for the endive variety. The pH values of the investigated substrates for both varieties showed a high value (8.7) for the GR exceeding the ones around 8.1 reached in PZ and PR. Regarding the EC-values, two pictures appeared under successive irrigation with saline water: the first, gradual increments in the EC-values of the collected drained nutrient solution reaching 4 dS/m and 4.5 4 dS/m for lettuce and endive varieties respectively and the second, regarding the substrates showing no changes in its EC-values, being more or less equal to their initial values. This clearly indicates that with the use of inert substrates, the accumulated salts due to frequent irrigation with saline water could be easily leached out, keeping the growing media at a relatively low salt concentration level, indicating the high potentiality of using saline water (EC=4 dS/m) for the production of green salad. The plant growth parameters did behave similarly under the different investigated substrates for both varieties. The yield of lettuce was nearly three times greater than that of endive (2.14 and 0.83 kg m -2 , respectively); for both varieties higher yields were observed on PZ and lower on GR. The yield on PR was intermediate.