Abstract
Effects of circulation frequencies of cultural solution after planting on growth, and fruit yield and quality were studied, in solution culture of tomato plants bearing only two trusses and planted in high density.
Tomato plants, which had grown at low dissolvedoxygen concentration in cultural solution from the stage of young seedlings, did not show wilt-symptom and root-rot at the low dissolved-oxygen concentration of 1.3 ppm after planting and could survive even at the concentration of 0.9 ppm which was maintained about 2 hours.
The relation between dissolved-oxygen concentration after planting and occurrence of puffy fruits was investigated. The degree of puffiness was indicated with specific gravity of fruit. The specific gravity of fruit which had marketable quality was above 0.90. In the culture of the plants sown from August to April, circulation frequencies of cultural solution in the nighttime (6 p.m.-6 a.m.) were decreased to 15 minutes in every 360 minutes almost until fruit setting in the second truss was ensured. After fruitsetting in the second truss, circulation frequencies of cultural solution in the nighttime were increased up to that in the daytime (6 a.m.-6 p.m.), which were 15 minutes in every 60 minutes. Such circulation frequencies for controlling dissolved-oxygen concentration prevented overgrowth of foliage and ensured high yield of fruits without puffiness. In the culture of the plants sown in July, the circulation frequencies above mentioned for controlling dissolved-oxygen concentration producted cracking fruits.
