ASABE Technical Library - Abstract

Abstract. For the efficiency of a closed hydroponic system used in greenhouses, an automated management system is needed for effectively supplying nutrients and controlling various environmental factors for plants. In this study, a WinCE-based embedded system consisting of an array of ion-selective electrodes (ISEs) and multiple metering pumps was developed to effectively manage concentrations of nutrients in recirculating hydroponic solution. An array of ion-selective electrodes (ISEs) based on PVC membranes was fabricated to measure the concentrations of NO₃^-, K⁺, and Ca²⁺ ions in recirculating hydroponic solution. A fertilizer dosing algorithm was developed to calculate the volumes of nutrient stock solutions to be supplied based on a comparison between the preset and present concentrations of the three different nutrients. Prior to the cultivation of Kale crop, a stepwise spiking test was conducted using the developed embedded system programmed based on the dosing algorithm to see if the system could formulate different concentrations of the three different nutrients as desired. The results showed that there were highly linear relationships between the target concentrations and the prepared concentrations (coefficients of determinations >0.9). However, studies on the decreased concentrations of Ca ions prepared as compared to the target concentrations were needed.