Abstract
Tomatoes were grown on substrates made of cedar bark to investigate the effects of decomposition changes in physiological and chemical properties of substrates, the concentrations of the components in the solution within the substrates, and the growth and yield of tomatoes. The substrates were fixed in a closed hydroponic system with a capillary uptake method. The liquid and gaseous phases of the substrates did not differ, while the solid phase decreased as decomposition proceeded. As decomposition progressed, the annual weight loss in the substrates grew smaller, CEC of the substrates increased, nitrogen absorption by the substrates decreased, and the NO3-N level in the solution within the substrates tended to fluctuate higher. K, Ca, Mg levels in the solution within the substrates were higher in substrate used for five years than in substrates used less than three years. There were no difference in stem diameter of tomato plants at the first and third clusters, except that plants showed thinner stems on the one-year-old substrate. The yield of tomato fruits tended to be higher on two-year-old substrate than on one-year-old substrate. The yield was lowest on the five-year-old substrate. It was suggested that the substrate be replaced after five years.
