Agriculture Reference
In-Depth Information
FIGURE 5.9
pH Up and pH Down solutions for adjusting the pH of nutri-
ent solutions. (Courtesy of Technaflora Plant Products, Ltd., Mission, British
Columbia, Canada.)
ELECTRICAL CONDUCTIVITY (EC) OF
THE NUTRIENT SOLUTION
Electrical conductivity is a measure of the nutrient solution's concentra-
tion through its ability to conduct electricity. Pure water does not con-
duct electricity, but any water having solutes (elements) added to it has the
capacity to conduct electricity. A special meter, an electrical conductivity
(EC) meter (Figure 5.10), measures the electricity conducted by the nutri-
ent solution, which is directly related to the level of total dissolved solutes
in the solution. The scale is commonly expressed as millimhos (mMhos)
or millisiemens (mS).
You cannot directly relate parts per million (ppm) to EC as different ions
conduct electricity at different efficiencies; therefore, the ratios of these
ions as well as their individual concentrations in the solution will influence
the electrical conductance. Electrical conductivity does inform you of the
overall concentration of all elements within the solution so it can be used
as a guide to tell whether the solution has adequate nutrients. But you could
still have an imbalance of individual ions, as the solution may have a high
