In comparison with traditional hydroponic culture, vegetables with low nitrate nitrogen levels are produced which cause health problems such as hemoglobinemia, carcinogenesis and liver damage.As for the material of hiradai, it is the mainstream that the styrofoam is put on the wooden frame and only the vinyl sheet is covered in the mainstream, but in this case, the stagnation of the leveling liquid without the horizontal level of the flat table is generated, and the dirt is sticky and it is unsanitary.Solution: the nutrient solution supply system is cultivated in the solution tank 2 before the harvest, and is switched to the mineral water tank (1) immediately before the harvest, and after lapse of 24 hours or more, the nitric acid nitrogen number is reduced.The horizontal layer was kept using FRP in the material of hiradai (4), and the solution was able to be made to an arbitrary water level.Moreover, it was possible to simplify the shelf cleaning work by using the characteristics of FRP which is hard to adhere to dirt.In addition, it is possible to stabilize the solution temperature by the adiabatic effect by the feature of FRP.Diagram【課題】従来の水耕栽培と比較して、ヘモグロビン血症や発ガン、肝障害などの健康障害を引き起こす硝酸態窒素数値の低い野菜を生産する。又、平台の素材には従来は木枠に発泡スチロールを敷き詰め、ビニールシートを被せただけのものが主流であるが、これでは平台の水平が取りずらく養液の滞りが発生し、汚れが付着しやすく不衛生であった。【解決手段】養液供給システムは収穫直前までは養液タンク▲2▼で栽培を行い、収穫直前にミネラル水タンク▲1▼に切り替え、24時間以上経過させて硝酸態窒素数値を低減させる。平台▲4▼の素材にFRPを用いて水平を保ち、養液を任意の水位にできるようにした。又、FRPの特徴で汚れが付着しにくい性質を利用して棚清掃作業の簡素化が可能とした。さらにFRPの特徴で断熱効果を利用して養液温度の安定化を図ることが可能である。【選択図】図1
