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GROWER
by Eric Hopper
Q
I am just starting to grow vegetables hydroponically in my small outdoor greenhouse. As the liquid
fertilizer gets used up how can I maintain the right levels of nutrients in it? How do I know how much
fertilizer to add in my continual mixes? And what is “EC level” that you keep referring to? I’m a beginner.
Thank you,
Tom
a T
hank you for your question. Maintaining the optimal
nutrient concentration in a hydroponic system will
allow your plants to continue to perform to their full poten-
tial. Each nutrient manufacturer has its own suggested
nutrient concentration for hydroponic applications. This is
usually expressed in either parts per million (PPM), total
dissolved solids (TDS), or electrical conductivity (EC). Most
hydroponic growers use a monitoring device that expresses
the nutrient concentration in the form of PPM or TDS. Parts
per million is a form of measurement used to determine the
concentration of diluted substances. One PPM is equal to
one milligram of substance per liter of water. In hydroponic
gardening, PPM or TDS is used to express the amount of
nutrients in the nutrient solution. In fact, PPM and TDS are
just different terms that actually express the same thing.
Even meters that express PPM/TDS measurements rely on
electrical conductivity that is automatically converted into
a PPM/TDS format. Some of the older meters do not auto-
matically convert the EC values into a PPM or TDS value. If
a grower is using an EC meter that expresses the nutrient
concentration in EC form, he or she may need to convert the
value to a PPM or TDS value in order to compare it to the
manufacturer’s PPM or TDS recommendation.
As the plants grow and use the individual elements in
the nutrient solution, most hydroponic growers simply
replace the used solution with a premixed nutrient
solution based on the manufacturer’s recommendations.
This is totally acceptable for the short term. However,
because nutrient meters express the total nutrient
concentrations and not individual elements, the actual
ratio of nutrients to one another may get out of whack
over time. If an individual nutrient concentration
becomes too low, the plants will not receive all that they
need to sustain accelerated growth rates. If a particular
individual nutrient gets over-concentrated, it may cause
serious burning or lock out issues, which can also lead
to nutrient deficiencies. Perhaps the best safeguard
against a nutrient solution with an undesirable ratio of
individual elements is to do a complete reservoir change
every two weeks or so. A periodic, complete reservoir
change removes the unbalanced nutrient solution and
replaces it with a fresh, balanced nutrient solution.
In summary, hydroponic gardeners should invest
in a decent nutrient meter to compare PPM or TDS
values to the manufacturer’s recommendations. To
safeguard against an unbalanced ratio of nutrients
that naturally occurs as the plants feed, a hydroponic
grower should do a periodic reservoir change. I hope
this answers your questions.
Keep on Growing,
Eric Hopper
EH Eric Hopper has more than 10 years of experience in the hydroponic industry as both a retail store manager and owner.
He continuously seeks new methods and products that could help maximize garden performance. Eric resides in Michigan
where he and his family strive for a self-sufficient and sustainable lifestyle.
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