H. Inden, Y. Kubota, S. Awaya
As the characteristics of ion absorption from hydroponic solutions differ because of environmental influences and plant stage, there will occur an undesirable change in the composition of hydroponic solutions. Usual management of the solution is done by adding stock solution according to the value of Electrical Conductivity (EC) readings. Because of differential uptake, this strategy of management tends to enlarge ion imbalances in solution. Determining the quantity of nutrient stocks to dispense is therefore complicated and the continuous, in-line, detection of a variety of ions is difficult. A program of aiding the mixture of macronutrients in nutrient solutions, named EasyMacro, was developed to calculate the quantity of nutrient stock to be added to the solution automatically. This software for adjusting macronutrient compositions is a personal computer spreadsheet program that runs on Lotus 1-2-3- R5J for Windows. The user specifies the desired solution composition in terms of milli-equivalents of macronutrients or contents (weight per volume) of macronutrients. EasyMacro determines the quantity of stock to be injected from differences in demand composition and the real-time macronutrient concentrations in solution. The ion contents of the solution are measured continuously by means of a multi-ion meter for nitrate (NO3), potassium (K+), calcium (Ca2+) and magnesium (Mg2+) ions. The combination of EasyMacro and the multi-ion meter could allow for accurate control of closed loop hydroponics solutions. This strategy of management may, in turn, result in higher crop yields, more efficient use of fertilizer and elimination of groundwater eutrophication due to the drainage of large amounts of nutrient solutions from open hydroponic systems.
Inden, H., Kubota, Y. and Awaya, S. (1999). AUTOMATIC ION CONTROL OF NUTRIENT SOLUTIONS. Acta Hortic. 481, 707-712
DOI: 10.17660/ActaHortic.1999.481.85
Macronutrients, Personal Computer Software, Multi-ion meter, Hydroponics

Acta Horticulturae