| 摘要 |
The trough in which the plants may be growing hydroponically is double walled. The water level within the trough is maintained by replenishment from a reservoir (4) within the double wall. Replenishment may be controlled by a ball valve. The reservoir may be a closed vessel whose only opening is into the trough at the required water level. When the water level in the trough falls below the outlet, air can enter the reservoir, and water can leave it, until the outlet is covered again. Provision is then made for blocking the outlet when the reservoir is opened for filling. |
