System design and analysis of a continuous monitoring of the environment in nutrient solution culture

A simple system for monitoring the environment of the nutrient solution in a hydroponic system has been designed and constructed. The system is capable of continuously measuring four parameters; temperature, pH, dissolved oxygen (DO) and electrical conductivity (EC). Unique features of the system include auto-calibration of the DO sensor and application of the four electrode principle for conductivity measurement. Results from a typical measuring day have revealed a daily cycle of pH and DO. These oscillations are explained by the large differences between air and water temperature. It was found that the efficiency of aeration was reduced when warm (45°C) greenhouse air was injected into relatively cold (25°C) nutrient solution. The present study suggests that continuous monitoring of the nutrient solution can improve its management and control as compared to the classical method of periodical analysis when growing plant hydroponically.