Advanced monitoring of hydroponic solutions using ion-selective electrodes and the internet of things: a review

Abstract

Hydroponic cultivation is a promising alternative that could address environmental and food issues. Hydroponic cultivation allows farmers to reduce the amount of fertilizers and water. Moreover, accurate monitoring of nutrient levels allows to optimize crop growth. For that, researchers have designed ion-selective electrodes as sensors and the internet of things for precise monitoring. Here we review the application of ion-selective electrodes in monitoring hydroponic solutions with focus on parameters, sensitivity, accuracy and the internet of things. We found that the targeted concentrations of nitrate and potassium are successfully maintained with errors of less than 10 mg L−1 by using polyvinyl chloride membrane based on ion-selective electrodes. Calcium electrodes show less sensitivity in detection of calcium ions in hydroponic solutions. Regular calibration sequence solved the stability issue of ion-selective electrodes. Compared to carbon nanotube-based ion-selective electrodes, the best results for sensing nitrates were obtained with polyvinyl chloride ion-selective membranes.