measure salt in soil

Alan S. Wicks NAP-4 at
Thu Oct 16 16:10:47 EST 1997

> My greenhouse soluble salt meter measures salts in ppm, and millimhos.
> Some of the research I've found indicates salt levels in EC units.
> and/or dSm(exponent)-1.  Can someone explain this in high school math
> level terms?  I have not had chemestry and need some help
> understanding
> this.
> One study class the low salt level 3dSm-1, and the high salt level
> 10dSm-1.  If the -1 is an exponent, it seems it should be visa
> versa.
> Thanks. Emily

Greetings Emily,

Yes, the -1 is an exponent - sort of.  It is a shorthand method of
saying 'per'.  That is, 10dSm-1 is read as 10 deciSiemens per meter.  So
10 dSm-1 is greater than 3 dSm-1.  The greater the number the greater
the concentration of ions.  EC does stand for Electrical Conductivity. 
Each crop has an upper limit of soil solution EC beyond which plant
growth is reduced.  Calcium in the soil solution increases this upper
limit so that crops that are normally affected by ECs above 2, for
instance, might not have any problem until 2.5 is the percentage of
calcium is high.

Hope that this helps.

If you have any more questions e-mail me directly since I don't always
get to spend as much time in the news groups as I would like.

Sincerely yours,

Alan S. Wicks

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