Effects of the Addition of Deep Seawater to a Nutrient Solution in Hydroponics on Growth, Fruit Yield and Quality of Tomatoes

The effects of adding deep seawater to a nutrient solution in hydroponics using organic substrates on the plant growth and fruit yield and quality of tomatoes pinched above the 4th truss were investigated. Deep seawater was added to the nutrient solution at concentrations of 20%, 10%, 2%, and 0%(control). With the addition of deep seawater at 2%, plant growth was almost the same as that of the control,but was depressed at 10 and 20%. The marketable fruit yield with 2% deep seawater addition was 65% of the control, while those of 10 and 20% additions were 36 and 38%, respectively. The reduction of marketable fruit yields by the addition of deep seawater was attributed to a decrease in fruit weight and number as well as an increase in defective fruit. However, the soluble solid content and titratable acidity of the fruit increased with the addition of deep seawater. The results indicated that the tomato fruit quality might be improved with the addition of deep seawater to a nutrient solution.