Different PH sweet spots for hydro & soil?

Brokeoldbloke

Brokeoldbloke

Active Member
I’m having trouble understanding why the PH sweet spot for nutrient absorption is is different when growing in hydro vs soil. I’ve seen 5.8 for hydro and 6.5 for soil as a general recommendation. But why is it not just one or the other for both?
 
lokie

lokie

Well-Known Member
Im no chemist.

I imagine it has to do with the differences in the compound elementary properties of H20 and soil.
 
cannabineer

cannabineer

Ursus marijanus
It has to do with kinetics ... the speed of release of bound nutrients.
In hydro there are no bound nutrients, and a slightly acidic medium gives the best compromise rate for their absorption.
In soil, there are bound nutrients (especially Ca, Mg, Fe and P) that would be released in toxic amounts with a too-sour pH. So the compromise point (best availability, no acute shortage of any one thing) is shifted toward neutrality. All jmo. cn
 
Brokeoldbloke

Brokeoldbloke

Active Member
Thanks lokie and cannabineer,
You both are saying similar things but I guess I'm a little too dense to understand. Why it is such a drastic difference especially with phosphorous, manganese, boron, copper and zinc? Every soil mixture is a little different and same goes for water with maybe the exception of distilled. Whats in the soil that causes the binding of the mineral elements?
If anyone has a suggestion for more info, I’m willing to do the research but could use a push in the right direction.

2rnagau.jpg
 
lokie

lokie

Well-Known Member
my suggestion is dont sweat the things you can not control.
[video=youtube;Oo4OnQpwjkc]http://www.youtube.com/watch?v=Oo4OnQpwjkc[/video]
 
Brokeoldbloke

Brokeoldbloke

Active Member
Well after googling for an hour or so. I finally stumbled on this from HydroEmpire.com:

"The electrical charges in soil particles are different from those in soilless mixes. For this reason, different pH levels for nutrient uptake are needed for each type of growing medium, depending upon each medium's CEC value."

So to answer my own question (I guess) and maybe someone's in future. The Cation Exchange Capacity (CEC) of soil is different than the CEC of a hydro system’s medium thus requires a different PH value for optimum nutrient uptake.
 
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