Abstract
We evaluated the use of pumice as a substrate for hydroponics of muskmelon. Overflows were made 0.0 cm, 2.5 cm, or 5.0 cm from internal bottom of bed to adjust the depth of nutrient solution in the bottom of bed (water level) . In 5.0 cm treatment, hermaphrodite flowers bloomed about 2 days earlier than in the other treatments. Soluble solids content of the fruits was about 15% in all treatments, but citric acid concent was significantly higher in 2.5 cm treatment than in 0.0 cm treatment with an associated decrease in solid-acid ratio. P, Ca, Mg and Mn contents of the fruits were maximum in 2.5 cm treatment, with P and Ca contents being significantly higher than those in 5.0 cm treatment, but K content was the highest in 5.0 cm treatment. Since growth of the plants was satisfactory and size and soluble solids content of the fruits were adequate at over 2.5 cm from internal bottom of bed, pumice is considered to be useful in hydroponics of muskmelon. Analysis of mineral elements in the drain indicated the marked decrease in P content in fruit developing period and excessive increase of EC in late stage of cultivation.
