| 摘要 |
PURPOSE:To reduce accumulation of effete matter and to stably carry out water culture of plant, by supplying new water to a circulating water culture solution at given intervals, exchanging part of the water culture solution with new water, replenishing a concentrated nutritive solution to the exchanged water culture solution until the solution reaches a given electric conductivity and automatically adjusting pH value. CONSTITUTION:In control of a water culture solution 1, first, water level of a water culture solution tank 3 is detected. When the water level is lower than a set water level L0, a solenoid valve 8 is opened, new water is supplied to the tank 3 and the water level is restored to the original level. Then, a solenoid valve 9 is opened, water is discharged until the water level reaches L1. At this point, a fixed amount of a solution 1 is exchanged with new water and simultaneously the solution in the tank 3 is stirred. Then, electric conductivity of the solution 1 is measured 15. When the measured value is lower than a set value, a concentrated nutritive solution is poured to the tank. Then the pH of the solution 1 is measured 14 and an acid or an alkali solution is fed to the tank so as to make the measured value become a set value. When pH becomes the set pH, a stirring pumup 18 is stopped and controlling process of the solution 1 is completed. |
