Abstract
From the viewpoint of conservation-oriented agriculture, this study investigated a closed cultivation system using a combination of rice hull substrate and TiO2 photocatalytic treat-ment of the waste nutrient solution. First, an extract of rice hulls in distilled water was treated with a TiO2-coated porous alumina filter under ultraviolet light irradiation. Then, rose (Rosa hybrida) rooted cuttings were soaked in the treated extract, untreated extract, or pure nutrient solution. The total weight of the shoot and leaves soaked in the photocatalytically treated extract was heavier than that in the untreated extract, and was similar to that in the pure nutrient solution. Next, rose growth was compared in three practical cultivation systems: two closed systems using rice hull substrate with photocatalytically treated or untreated waste nutrient solution (photocatalytically treated and untreated systems), and an open system using rockwool substrate (current system). The growth and yield in the photocatalytically treated system were significantly greater than those in the untreated system and were comparable to those in the current system. These results show that the TiO2 photocatalytic treatment of the waste nutrient solution is effective in closed soilless cultivation using rice hull substrate.
