"David Hare-Scott" schreef in bericht ...
Alex wrote:
"David Hare-Scott" schreef in bericht
...
David E. Ross wrote:
On 9/14/2009 12:44 PM, Alex wrote:
Hi,

I would like to know what the correct EC is for the potting soil of
various plants.

Is there any website that has this information?

Thanks



What is "EC"?

Electrical Conductivity. Used as a measure of dissolved salts.

David

Right. Most descriptions for plants say 'use a light mix' or something
like that - I want to be precise and know exactly what my plants
are going to need, and what they're getting, which is why I measure
runoff with an EC meter.


I don't think this will work.

However, it is difficult to find the correct EC (or ppm/parts per
millions) for plants online.


I don't think this will help much, if at all.

So I am wondering if someone has come a across a website
or a book which gives you good information over what to use.

Alex

I am not sure that there is a "correct" EC for each plant. A given EC is
the result of the agregate of the dissolved salts in the sample but
depending on the combination of cations and anions that make it up it could
be suitable or unsuitable for a growing medium. For example an EC of "X"
might be made up of a good balance of salts supplying all the major and
minor elements or the result of just sodium chloride. Also the presence of
certain quantities of soluble minerals is not a good indication of solid
medium fertility as some quite adequate nutrients may be available as partly
soluble compounds which contribute little to the EC reading. Likewise an EC
in the "correct" range will not tell you if some trace elements are missing.

My understanding is that EC is used to estimate when excessive salts might
be present. The higher the EC the fewer types of plants that will grow in it
assuming that the correct elements are present. Thus it can assist in saying
if medium is unsuitable (the EC is too high for the plant to tolerate) but
cannot say if it is suitable (the correct balance of nutrients are
available). For example plants adapted to growing in salt pans etc can
tolerate a much higher EC than others.

The reason I have qualified what I have said here is that I don't use EC in
growing and I am speaking from theory. Do you have a reference that says
that EC can be used the way that you describe?

David

The reason I think using EC as a measure of required nutrient strenght
or flushing, is that

1) Short of soil testing, you can use runoff as an indication of what
is going on in your soil
2) EC is much more precise a measure than the usual 'use 2 ml per
liter' when it comes to nutrient solution
3) EC is very important in hydroponics, so why shouldn't it be
in soil or oranic growing media?

It cannot tell you how much of a specific nutrient is available/missing,
but it can give you clues about how much to use.

So I just have to wonder - what is the optimal EC for soil of
various plants?

I haven't found a lot of literature dealing with this.

Alex