In Japan, main of hydroponic culture is run-to-waste system and rockwool as a substrate. To reduce environmental problems, recycling of nutrient solution and using organic substrate such as rice chaff and coir as a substitute for rockwool are anticipated. However, they cause the accumulation of organic pollutants from plant and organic substrate in the nutrient solution, which results in the inhibition of the plant growth.
We tried to decompose the organic pollutants utilizing TiO₂ photocatalyst under the solar illumination, and to establish a new raising seedling system and hydroponic culture system.
New systems are shown in Figure 1. Tomatos were planted on the system. New photocatalyst was developed with low-cost material and TiO₂ . The raising seedling system with this photocatalyst and Ag.
The amount of Total Organic Carbon in the wastewater after the TiO₂ treatment was lower than before in both systems. Using Ag together with photocatalyst for the raising seedling system, there was less number of the attack stocks than time only using Ag.
These results show that new TiO₂ materials under the solar illumination can be actually used in new raising seedling system and hydroponic culture system, leading an environmentally friendly agriculture.