Research On Disinfection And Sterilization Of Circulating Nutrient Solution Of Hydroponic Fast-growing Cabbage And Its Integrated Equipment Design

High temperature associated bacterial diseases often occur during the cultivation of hydroponic leafy vegetables in summer,which restricts the development of soilless culture industry.In response to this situation that hydroponic fast-growing cabbage are prone to disease,the thesis investigated the disinfection of circulating nutrient solution,mainly on the effect of circulating nutrient solution under different temperature treatments on the incidence of rot disease and the growth and quality of fast-growing cabbage plants and the effect of different frequencies of ozone disinfection treatments on the incidence of rot disease,the content of pathogenic bacteria in circulating nutrient solution and the growth and biofortification effect of fast-growing cabbage plants.Finally,a new soilless culture nutrient solution disinfection system was optimized and designed by modifying the existing piped hydroponic system and combining sensor information technology and intelligent regulation and control.The main points of this study are as follows:(1)By isolating and culturing on semi-selective NA medium,from biological observation,pathogenicity experiments,and 16S rRNA sequence PCR amplification and sequencing using universal primer 27F/1492R,and comparing with the database thus identifying as Fusarium citricola.(2)The temperature of the nutrient solution in the storage tank was controlled by an external thermostat controller and a water pump to form a cooling and heating automatic thermostat control system and circulation system.The incidence rate was 8%,and the incidence rate was 0%at 22 ℃ and below.Controlling the liquid temperature of the circulating nutrient solution could effectively control the rots of summer fast-growing cabbage,and the soluble sugar content,soluble protein content and net photosynthetic rate were the highest in the treatment T2 group(22 ℃).Combining the reduction of plant morbidity and the effect on the quality of fast-growing cabbage,it can be considered that treatment group T2,i.e.,controlling the nutrient solution temperature at 22℃,is the optimal treatment group.(3)In the experiment,we found that the number of strains in the nutrient solution decreased with the increase of the frequency of ozone,and the incidence rate of fast-growing cabbage also decreased gradually.The incidence rate was 6%in the T2 and T1 treatment groups,and 0%in the T3 group.From the experimental results,it can be seen that ozonation of the nutrient solution can effectively control the incidence of bacterial rot of fast-growing cabbage plants.At the same time,the soluble sugar content of snap beet increased with the frequency of ozonation,and the effect on chlorophyll and soluble protein content of snap beet leaves showed a parabolic trend and reached the optimum at T2 treatment,while it had a negative effect on Vc content of snap beet.Among the three treatments,the T2 treatment,in which ozone was applied once every three days for 10 min,was the best treatment.The physiological strengthening effect of soluble sugar was the best.(4)A new type of soilless nutrient disinfection system was developed and designed.The soilless cultivation disinfection system is based on the pipeline type circulating hydroponic planting system,with the addition of ozone generation device system,which makes ozone in the dsinfection system and ultrasonic oscillator to disinfect the circulating nutrient solution.The intelligent control of the whole soilless culture disinfection system is achieved through this system.The disinfection system designed in this study is characterized by simple operation and can automatically complete the entire disinfection process.