Abstract
This study aimed to establish a non-drainage hydroponic system with a coconut coir substrate by a frequency domain reflectometry (FDR) sensor in controlling irrigation to set volumetric water levels in tomato (Solanum lycopersicum L. Starbuck 1) cultivation in the autumn to winter season. When the volumetric water content was controlled at 40 or 50%, daily-averaged irrigation amounts were roughly half those needed when the water content was set at 60%. In the 40 and 50% treatments, there was no drainage, and the water contents and electrical conductivity (EC) levels in the substrate during irrigation-off hours were lower than during irrigation hours. In the 60% treatment, the average rate of drainage was 15% of the total irrigation, and the EC level in the substrate increased during the irrigation-off hours. Further research is needed to verify this result during a summer season.