PROBLEM TO BE SOLVED: To provide a hydroponic cultivation means that can accelerate the hypertrophy of a harvest site of a root in root crops.SOLUTION: The hydroponic cultivation system includes a cultivation tank 1 of performing the hydroponic cultivation of the root crops, and a preliminary tank 2 for circulating water culture medium W. A liquid supply means 3 is installed in one end 11 of the cultivation tank 1, and a liquid discharge means 4 is installed in the other end 12. The water culture medium W to be stored in the preliminary tank 2 is supplied to the cultivation tank 1 by driving the liquid supply means 3, and the water culture medium W to be stored in the cultivation tank 1 is discharged to the preliminary tank 2 by the liquid discharge means 4. Thus, the hydroponic cultivation system includes a mechanism for circulating the water culture medium W. The liquid supply means 3 is controlled to be driven periodically for a fixed time. The liquid discharge means 4 has a shallow discharge part 5 and a deep discharge part 6. The shallow discharge part 5 is configured to discharge the water culture medium W to the preliminary tank 2 from the shallow part of the cultivation tank 1. The deep discharge part 6 is configured to discharge the water culture medium W to the preliminary tank 2 after ascending from deep part of the cultivation tank 1 up to near the upper limit height W1 of the water level in the cultivation tank 1 in accordance with the principle of siphon.SELECTED DRAWING: Figure 1【課題】根物作物において、根部の収穫部位をより肥大させることのできる水耕栽培手段を提供する。【解決手段】根物作物の水耕栽培を行う栽培槽1と、水耕液Wを循環させるための予備槽2を備え、栽培槽1の一端側11には液供給手段3が、他端側12には液排出手段4が設置され、液供給手段3を駆動することにより、予備槽2に貯留する水耕液Wを栽培槽1へ供給するとともに、液排出手段4により、栽培槽1に貯留する水耕液Wを予備槽2へ排出させることで水耕液Wを循環させる機構を備え、液供給手段3は定期的に一定時間駆動するように制御され、液排出手段4は浅部排出部5及び深部排出部6を有し、浅部排出部5は、水耕液Wを栽培槽1の浅部から予備槽2に排出する構成であり、深部排出部6は、サイフォンの原理により、水耕液Wを、栽培槽1の深部から栽培槽1内の水位の上限の高さW1付近まで上行させた後、予備槽2に排出する構成とする。【選択図】図１
