Agriculture Reference
In-Depth Information
FIGURE 5.10
An electrical conductivity (EC) meter to measure total dissolved
solutes in a nutrient solution.
level of a very highly conductive element such as potassium and a low level
of one that conducts less electricity such as nitrate ions. So, remember, the
EC gives you only an idea of the overall total dissolved salts within the
solution. To determine the exact levels of each element, you would have to
submit a sample of the nutrient solution for atomic absorption analysis in a
private laboratory. Such an analysis would cost about $45 to $60.
EC meters are essential for anyone growing hydroponically, as they
assist in monitoring the nutrient levels of the solution. There are many
makes on the market from pen types that cost about $100 to combina-
tion pH, EC, total dissolved solutes (TDS), and temperature testers that
cost about $200 to the more sophisticated handheld portable meters in the
range of $200 (Figure 5.11). These meters are often 3-in-1 meters for test-
ing pH, EC, and TDS (Figure 5.12). Generally, a nutrient solution may have
an EC of 1.5 to 3.0 mMhos.
The best is to test the solution as soon as you make it. Record this value,
then test and record the EC every day. That will tell you of weakening
trends in the nutrient solution as the EC goes down over a period of several
weeks. At some point, often within a month, the EC will fall enough to
justify changing the entire nutrient solution. The EC meter then indicates
at what time you need to change the solution before deficiencies may occur.
With experience and a few solution analyses by a laboratory you can relate
