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

为改进和推广杉柏压缩床水培技术，研制杉柏压缩床水培自动灌溉加热系统。为此，对床层的物性、持水性能、干燥特性和导热系数进行了研究。(1)床中所含的精油阻断了吸水。由于淹水，床变成了吸水性。床中含有的精油被认为能有效防止床的腐烂。床被水浸湿了。用水浸透它需要12个小时。把床弄湿后，用网子把多余的水排掉。5分钟后，固相、液相、气相的表观体积分布分别为26%、28%、46%。这种大的气相比表明气体渗透性高。(4)在生物质床上种植圣女果，测定其生长情况和床内pF值，探讨灌溉的最佳控制。(5)秸秆直径的响应时间随着pF值的增大而增大。蒸腾流量随pF值的增大而减小。结果表明，灌溉树皮床的pF值应小于1.6 ~ 1.7，有利于圣女果的生长。(6)生物质床的导热系数约为岩棉床的1/3。低导热系数节省了床层的加热能量。结果表明，杉木和柏木的树皮材料适合用于水培床。

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.