OPTIMUM CONTROL OF IRRIGATION SYSTEM FOR HYDROCULTURE USING BIOMASS BED WITH TWO INPUTS OF TRANSPIRATION AND WATER CONTENTS

本研究旨在改进和推广水杉、柏木压床栽培技术，并研制水杉、柏木压床栽培自动化、灌溉和加热系统。为此，对该床层的物理性能、持水性能、干燥性能和导热性能进行了研究。(1)包含在床中的精油中断了水的吸收。由于浸水，床变得吸水。床中含有的精油被认为是有效防止床腐烂的。(2)床被洪水弄湿了。在浸水后，用水使其饱和所需的时间为12小时。(3)润湿后，将床放在网中以排出多余的水。5分钟后，固、液、气相的表观体积分布分别为26%、28%和46%。这种大的气相比率表明气体渗透性高。(4)在生物质床中种植樱桃番茄，测定其生长和生物质床的pF值，以探讨最佳的灌溉控制。(5)茎径的响应时间随pF值的增加而增加。蒸腾流量随pF值的增大而减小。因此，建议樱桃番茄生长所需的灌溉皮床pF值应小于1.6-1.7。(6)生物质床的导热系数约为岩棉床的1/3。传热系数低，节省了床层的热能，因此，日本柏木和柏树的树皮材料被认为是适合用于水培床的材料。

This study was done to improve and popularize the hydro- cultivation with the compressed bed of Japanese cedar and cypress, and to develop an automatic, irrigation and heating systems for that. Therefore, physical properties, water holding performance, drying characteristic and heat couductivity of the bed were investigated.(1) The essential oil that is contained in the bed interrupts the water absorption. The bed became absorbent of water by flooding in the water. The essential oil that is contained in the bed was considered effective to prevent the rot of the bed.(2) The bed was moistened by flooding into the water. Time required to saturate it with water was 12 hours after flooding it.(3) After moistening, the bed was put n a net to drain the excess water. After five minutes, the apparent volume distribution of solid, liquid and gas phases were 26,28 and 46% respectively. This large ratio of gas phase showed that the gas permeability was high.(4) Cherry tomatoes were planted in the biomass bed, and its growth and the pF value of the bed were measured to investigate optimum control of the irrigation.(5) The response time of the stalk diameter increased with the pF value. The transpiration flow rate decreased with the increasing pF value. It was suggested that the pF value in the irrigated bark bed should be less than 1.6-1.7 for the growth of cherry tomatoes.(6) The thermal conductivity of the biomass bed was about 1/3 of that of the rock wool bed. The low thermal conductivity saves the heating energy of the bed.Consequently, the bark materials of Japanese ceder and cypress were considered suitable for the hydro-cultivation bed.