WATER AND NUTRIENT USE EFFICIENCY OF TOMATO SOILLESS CULTURE AS AFFECTED BY IRRIGATION METHOD AND WATER QUALITY

      The paper report the main results of an experiment conducted to compare different irrigation methods for tomato soilless culture.
The plants were grown in pots filled with a peat-perlite mix in a temperature controlled glasshouse.
Seven cultivation techniques were compared: 1) open system with drip irrigation and 3 mM NaCl enriched nutrient solution (NaCl-NS) (control treatment); 2) semi-closed system with pan placed under pots, drip irrigation and NaCl-NS; 3) semi-closed system with pan placed under pots, subirrigation, NaCl-NS; 4) as in 3, but using nutrient solution not enriched with NaCl; 5) closed system (recirculating nutrient solution) with drip irrigation and NaCl-NS; 6) closed system with subirrigation and NaCl-NS; 7) as in 6, but using nutrient solution not enriched with NaCl.
In closed systems the recirculating nutrient solution was discharged when NaCl concentration was higher than 8 mM. Both the semi-closed and the closed systems reduced nutrient runoff of more than 80% compared to open system.
The nutrient solution was diluted in semi-closed and closed systems to avoid substrate salinisation; this resulted in nutrient deficiency and, compared to control, decreased marketable yield in semi-closed system with subirrigation and in closed system with drip irrigation, but non in the semi-closed system with drip irrigation.