Development of Supply System of Microbubble Ozonated Water in Agriculture

The demand for safe vegetables and fruits that do not rely on agricultural chemicals is growing. As a result, ozone has attracted attention as a new sterilization method in agriculture, but there are problems in utilizing ozone gas from the point of view of safety. Although ozone in its liquid state (in which it is dissolved in water) would be of a more practical use, ozone gas is hard to dissolve in water. This study was performed to determine the effectiveness of microbubble ozonated water. Microbubbles help to achieve a high dissolution rate for gaseous ozone in water. The time taken to achieve a certain concentration of ozone dissolved in water was reduced by half and was maintained for as much as three times longer compared with conventional aeration technology. No damage occurred to crop stems and leaves when sprayed with the microbubble ozonated water; however, if part of the culture solution was infested by a pest in the circulating soilless culture, it could cause the death of all plants. A bacterial withering disease of the tomato was completely controlled by a 5 ppm concentration of ozone in microbubbling water. Growth inhibition was not observed even though the root of the tomato was submerged in a high concentration of ozone (18 ppm) in water. Growth of Brassica rapa L. in a circulating soilless culture (NFT system) was promoted by using microbubble ozonated water. The growth and yield of strawberries was also promoted by spraying the stems and leaves with microbubble ozonated water. In addition, the injection of ozonated water into soil controlled the generation of weeds. Furthermore, the effectiveness of this application increased as the frequency of processing increased. These results indicate that it is possible to achieve safe agriculture and environmental conservation, without depending on agricultural chemicals, by using microbubble ozonated water.