Electrical conductivity (EC) can be used to compare the relative overall
nutrient concentrations of different brands of otherwise similar types of
This is done by measuring the EC value of the nutrient when diluted 100
fold (10ml into 1,000ml) with distilled water. To do this, add the
following volumes* to 1,000ml (1.05 Qrt) of distilled water:
1-parts: 10ml of nutrient.
2-parts: 5ml of part ‘A’ + 5ml of part
3-parts: Collect a total of 10ml from
all 3 bottles in accordance with the ratio of parts used to achieve a
given formulation type. For example, 10ml of ‘bloom’ formulation may be
comprised of 4ml part ‘A’ + 4ml part ‘B’ + 2ml part ‘C’.
Typically, the strongest 2 & 3-parts yield
between 2.4 and 3.0mS. Comparable, “slurry” type 1-part’s can far exceed
3.0mS - see Graph 7.40.
*For accuracy, use a finely graded pipette
(or equivalent device) for measuring out the nutrient.
Note: This method does contain a degree of
error because the conductivity of different mineral salts varies (See
“Effect of salt type”).