Ozone disinfection of three soilborne pathogens in nutrient solution

Experiments were conducted to determine the rising and attenuation performance of ozone concentration in nutrient solution, and the relationship between 99.99% sterilization rate of three plant pathogens and ozone concentration and the contact time. Experimental results showed that the higher the concentration of ozone air was, the higher the equation concentration of ozone in water was, and the shorter time was needed. Otherwise the lower the concentration of ozone air was, the lower the equation concentration of ozone in water was and the longer time was needed. When the ozone concentration was 0.24～0.48 mg/L and contact time was 2 min, the sterilization rates of the cucumber and tomato wilt pathogens, the mustard family soft rot pathogens were 99%, 99%, 99.3%, respectively. When the ozone concentration was 0.6 mg/L and contact time was 5 min, the three pathogens, i.e., the cucumber and tomato wilt pathogens with initial concentration of 10³ cfu/mL, the mustard family soft rot pathogens with initial concentration of 10⁶ cfu/mL, in nutrient solution were totally killed. It was demonstrated that remaining ozone in nutrient solution was harmful to the cucumber root which had germinated for 72 h. After the roots were treated by 0.54～0.60 mg/L and 0.64～0.72 mg/L ozone for 30 min, the injury rates were 7.7%, 22.2%, respectively. The results indicated that ozone could kill the pathogens of epiphyte and bacteria in the nutrient solution effectively, but the nutrient solution could not be applied to irrigate plants immediately after being treated by ozone.