Evaluating irrigation scheduling of hydroponic tomato in Navarra, Spain

The correct supply of water and nutrients is important in hydroponic growing systems in order to use water efficiently, avoid stress situations, and control production. The present study was conducted to evaluate two irrigation scheduling techniques for hydroponic tomato production in Navarra, northern Spain, related to the crop water requirements. The results show that although daily over-irrigation was applied (45.7% of drainage), 18% of the total yield (35 kg m(-2)) was affected by blossom-end rot problems, due to water stress suffered by the crop. Irrigation scheduling by time clock was not flexible enough to satisfy the varying crop water requirements through the day and during the season. With constant irrigation intervals and volumes, water and fertilisers were wasted during the morning (excessive irrigation) whereas during the afternoon, the plants suffered water stress. Irrigation scheduling by radiation method at a level of 0.81 MJ m(-2), with some supplementary time clock irrigation applications during the hours of darkness (in order to keep the growing medium wet), appeared to be a good solution. Copyright (C) 2003 John Wiley Sons, Ltd.