Construction of an Automatic Nutrient Solution Management System for Hydroponics-Adjustment of the K+-Concentration and Volume of Water

An automatic management system for nutrient solutions was constructed using a programmable logic controller (PLC) and a K+-ion selective electrode (K+-ISE). The concentration of K+was monitored by the K+-ISE. When the concentration of K+fell to the threshold limit, an appropriate amount of a concentrated K+solution was added to the hydroponic solution. The volume was also maintained at a constant level by addition of water. This system can be constructed simply and inexpensively without any computers and pumps.