Relationships between Plant Size and Amount of Overhead Irrigation Required for Uniform Water Supply to Individual Cell Medium

In order to clarify the problems with overhead irrigation systems for cell transplant production, uniformity of water supply by a boom spraying system was investigated. Furthermore, uneven water soaking into individual cell medium caused by plant cover growing in such cells was investigated. The amount of water supply from a boom spraying system varied considerable with the arrangement of the nozzles. Although a larger number of nozzles was set on the boom, the maximum amount of supplied water in the central part of the boom was about twice as much as that at each end of the boom. When no plant was grown in the cells, uniform water supply to individual cell mudium was obtained by a downright sprinkler system. However, when stock (Matthiola incana R. Br.) plants were grown in cells, variation in the amount of water soaking into the medium increased noticeably with increase in the plant size growing in the cells and with a decrease in the amount of supplied water. Plant covers with overlapped leaves may disturb the uniformity in the amount of water soaked into individual cell medium. As twice the water consumption may be required for uniform water supply into individual cell medium with an overhead irrigation system, a subirrigation system may be desirable for economical and ecological automatic irrigation to produce cell transplants on a large scale.