The Study On The New Aeroponic Growing Device Based On The Change Of Nutrient Solution Characteristics

The aeroponic is a kind of international advanced hydroponics way, which solvesconflicts between water, fertilizer and air in the best way. However, its widespreadpopularization and application still need the support of the intellectualizedmanagement technology. The change of nutrient solution characteristics and thepower failure will have the immeasurable effect on the system of the aeroponic,because the circulating way of nutrient solution cultivation completely relies onelectrical energy. The miniature aeroponic device, which is used and operatedconveniently and can effectively manage the nutrient solution and root systemenvironment, has important practical value to scientific research and home grown. Atthe same time, the most of existing aeroponic systems are huge in size, which not onlybrings the users disadvantages, but also restricts the location where it can be utilized.Lettuce is selected as an object. It is planted by aeroponic method. Firstly，change rules of nutrient solution characteristics including pH of the nutrient solution,the electrical conductivity, the temperature of the nutrient solution and thetemperature of the root domain are analyzed. In addition, conclusions are drawn byexperiment as:①in the lettuce’s initial growth stage(1-10days) after transplanting,the acid-base environment of the nutrient solution, whose initial pH is6±0.2, is themost stable, and nutrients are absorbed rapidly;②in lettuce’s different growth stages,the pH value and EC change rule of the nutrient solution are different;③the mannerof regularly replacing the nutrient solution completely is advantageous to the growthof the lettuce;④the stability of the root domain is affected by the externalenvironment and light greatly, and it is discovered through the relevant analysis, thecorrelation coefficient (r) between the external environment and the temperature ofthe nutrient solution is0.579, and the correlation coefficient between the light and thetemperature of the nutrient solution is0.598;⑤controlling the temperature of thenutrient solution has a direct effect on maintaining the pH and EC values of thenutrient solution, especially between25℃and30℃.Combined with the result of the experimental research and as to problems of theexisting aeroponic growing device, on the basis of the existing miniature device,designing the new aeroponic growing device to achieve that monitor and show theroot system environment of the aeroponic growing plants in real time, and switch the power supply after a short time of the power failure, and improve the cushioningproperty of the root system environment of the aeroponic growing plants from theaspect of designing the thermal insulation of the growing device, the new aeroponicgrowing device0.037m3is designed and developed. The single chip microcomputerAT89C52is made as the core of the study’s controlling system, A/D converterADC0809and12864display screen, the circuit design of each part are completed.Also monitoring values of pH, EC and temperature in real time and the seamlessconnection of the power supply and battery are achieved. It is shown that the pH andEC collecting circuit has good stability. The maximum error of pH is measured to be0.38, and EC is0.2ms/cm, which is satisfying. Nevertheless, in order to improve theaccuracy further, the electrode should be replaced regularly, and make sure that thesolution is prepared in the situation of the temperature of25℃accurately.At the same time, based on the principle of agricultural facility exterior-protectedconstruction thermal insulation, the scheme of two sets of the detachable "doublebarrel type" thermal insulating layer is designed. By comparison experiments, thefinal scheme is that polypropylene (PP) is used as inside and outside barrel walls, withthe interval of2cm, the inside is fulfilled with polyurethane foam, and the outside isstuck by aluminium foil. Effect experiments show, when the temperature in thegreenhouse reaches48℃, the temperature of the solution in the barrel with thermalinsulating structure can be maintained between25℃and29℃.Through the contrast test of cultivation effect with the existing miniatureaeroponic growing device, it is found that compared with traditional aeroponicgrowing barrel, the new one can improve the weight of the fresh lettuce to28.4%, thechanging rule of the nutrient solution pH and EC values is stronger, in addition, whenthe maximum temperature in the greenhouse reaches40℃, the root systemtemperature environment of the grown vegetable can be maintained stable, and mostof the time it is below25℃, and more than25%of the labor workload is reduced.Therefore, the application of the new aeroponic growing device has achieved theoverall objective designed for the device.