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Automated Sensing and Control of Hydroponic Macronutrients Using a Computer-controlled System
Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org
Citation: Paper number 131594020, 2013 Kansas City, Missouri, July 21 - July 24, 2013. (doi: http://dx.doi.org/10.13031/aim.20131594020) @2013
Authors: Dae Hyun Jung, Hak-jin Kim, Won Kyung Kim, Chang Ik Kang, Gyeong-Lee Choi
Keywords: Ion-Selective Electrode Hydroponic nutrients Macronutrients Control Injection time Lettuce solution
Abstract A recirculating hydroponic system based on EC-control is not efficient in managing the composition of individual ions in the solution, thereby resulting in a high increase in total concentration of the nutrients and an imbalance of the nutrient salts. This study reports on the development and evaluation of a computer-controlled system with an array of ion-selective electrodes (ISEs) and four diaphragm pumps for direct measurement and individual control of macronutrients in recirculating hydroponic solutions. The ability of three PVC membrane-based ISEs for simultaneous determination of NO3-, K+, and Ca2+ ions in the closed soilless system was evaluated. A computer program was developed with NI LabVIEW, which could calculate the volumes of individual nutrient stock solutions to be supplied based on real-time measurements of NO3-K-Ca ions, and vary the injection times of the metering pumps working at constant injection rates. A performance test of the developed sensing and control system was conducted by varying the concentrations of macronutrients in original lettuce solution contained in a hydroponic tank. The results showed that the NO3–K-Ca ISEs exhibited satisfactory performance in measuring nutrient concentrations in hydroponic solution and the target concentrations were prepared as expected when using the automated nutrient management system, showing linear relationships with high determination coefficient of >0.9 between the ISE- dosing methods and standard analyzers.
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