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

Abstract

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.