The changes in pH and electrical conductivity are the most common methods to determine when to add nutrient to hydroponic systems. These two measures provide general concentration information rather than the specific concentrations for the many nutrients. Furthermore, the various nutrients are not consumed at the same rate. After addition of stock nutrient mixture to an existing system, the concentrations of those nutrients consumed at slower rates increases and can become toxic. By using atomic absorption spectroscopy the concentrations of metals such as Ca, Mg, and Fe can be determined. Weekly testing of the pH and electrical conductivity and measurement of metal ions concentration by AA provides a correlation between the general measurement and metal concentration. Lettuce was grown in two nutrient film technique tables (Crop King) with different nutrient solutions.

Analysis of metal ion absorption compared to pH and conductivity changes in hydroponic growing systems

249th National Meeting (2015)

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