セル成型苗個体群の蒸発散量計測に基づく自動干満潅水システムの開発

Abstract

Soil-mix moisture in a plug tray with limited-volume can be easily changed by watering and evapotranspiration from a plug sheet consisting of plug seedlings, soil mix and a tray. Thus, timing and amount of watering are most important parts of skills in plug seedling production. An automatic ebb-and-flood watering system for controlling soil-mix moisture in a plug tray was developed and applied to tomato plug sheets. A plug tray with 128 cells (2.8 L/tray volume) was used for the experiment. The plug sheets were placed on a bench with an ebb-and-flood system. A plug sheet located in the center of the bench was weighed with an electric balance by suspending it from a steel frame. When integrated evapotranspiration of the plug sheet, estimated from decrease in weight of the plug sheet, reached over a setpoint of 1 100 g/tray during the daytime, all the plug sheets were watered from below. After the water in the bench drained, the integrated evapotranspiration was reset to zero. In this way, soil-mix moisture in the plug tray was controlled accurately in a proper range for growth of the plug seedlings during the culture period.