Scrowgdawg's Current Journal re Measuring Nutrients

Scrogdawg;3791089 said:

I've been asked why I measure EC instead of ppm's in the past. I came across this tonight and it explains the reasoning better than I ever could. A good little read anyway.
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Nutrient strength is a key factor in proper
plant nutrition. A nutrient strength meter is
an essential tool for the advanced grower.

There are two types of meters that measure
nutrient strength: parts-per-million (ppm) meters
and electrical conductivity (EC) meters. Both
types make the same measurement, but then
present the result in different units. Nutrient
strength is measured by passing an electric
current through the solution: The more easily
the electricity travels, the stronger the solution.
An electrical conductivity meter gives this result
as an electrical value, such as a millisiemen (mS).
This number is directly related to the strength of
the nutrient.

A ppm meter measures the conductivity of the
solution, and then attempts to estimate the
actual parts per million. The problem with this
method is that different meters may use different
scales to convert conductivity measurements
to ppm readings, so two different ppm meters
could read drastically different values in the exact
same nutrient solution.

A ppm meter is still a useful tool to a gardener,
but it is important to know that different meters
use different scales, and that 500 ppm does not
always mean 500 ppm. Knowing which scale your
meter uses will help you avoid underfeeding or
overfeeding. If you get advice about ppm values,
be aware that it might not translate directly to
your garden. Using an EC meter will eliminate
ppm confusion; however, if used properly any
meter will allow the gardener to track changes
in nutrient strength and make decisions and
adjustments that will contribute to success.

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