ELECTRICAL CONDUCTIVITY
Perhaps the most universal and favored
method of ion measurement, electrical
conductivity (EC), is the go-to method
for many scientists and researchers,
especially in the US. Although not
solely designated for nutrient moni-
toring, EC is a measure of electrically
charged nutrient ions in a solution and
is reported in the unit Siemens (S).
There is a positive correlation between
the ion concentration (or salt content)
of a solution to the EC; as one goes up,
so does the other. Deionized water and
reverse osmosis (RO) water theoreti-
cally should have ECs of zero, as both
undergo a process to eliminate the
contents of the solution that produce a
charge. In hydroponics, the EC of most
nutrient solutions ranges from 0.0-1.6,
depending on stage of growth. Certain
recirculating hydroponic applications
facilitate lower ECs, depending on other
factors including dissolved oxygen (DO)
content and the frequency of nutrient
solution delivery and changeout. Soil,
coco coir, and other drain-to-waste
applications typically require higher
ECs than hydroponics. This is due to
the fact that the plant roots in drain-to-
waste applications aren’t continuously
exposed to nutrient solution, so the
nutrient strength at delivery must be
slightly elevated to ensure proper
absorption potential.
TOTAL DISSOLVED SOLIDS/PARTS PER MILLION
Despite the fancy lingo, all of this
essentially means the same t