Subject: Low Soil pH Treatment?

From: [email-masked] (SMITTOLA)
Date: 2 Oct 1996 22:51:11 -0400

We grow an acre of commercial cut roses in a greenhouse.
All are grown in ground beds and are injector fed every irrigation.  Soil
and tissue test are perfomed monthly and feed mix is adjusted as needed. 
We have been fighting low soil pH's for a couple of years (4.5-5.5). Roses
grow ideal at 5.7-6.7 for maximun feed uptake. 

We have limed the beds several times, but since the it cannot be worked
into the ground with the rose bushes in place, we have to relie on a very
slow breakdown from the irrigation.  These lime treatments have hardly
brought the  pH up at all.  I have now started injecting Pottasium
Hydroxide (KOH) in with our feed, which of coarse is a strong base. I am
putting the total feed solution out at a pH of 9.2 and [email-masked]. I had to
adjust the K in the stock solution to balance out to the 4 meq/l that I
normally feed.  After using the KOH for about six months, I am finally
starting to see the pH climb to about 5-6 pH.  The plants look really
good, but I'd still like to get to the mid 6 pH range.

Does any one have any other suggestions or experience in this area? 

Steve Schmidt

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From: "Charles P. McCarthy" <[email-masked]>
Date: Thu, 03 Oct 1996 02:11:16 -0700

SMITTOLA wrote:
[edit]
> We have been fighting low soil pH's for a couple of years (4.5-5.5). 
[edit]
>After using the KOH for about six months, I am finally

Sounds like you're on the right track.  You should hit 6.5 in approx. 
3 mos. 

"If it ain't broke don't fix it."  And if what you're doing's working,
don't mess with it!  Once you achieve your target pH you can titrate
your KOH dosage down to a maintainence level, and you're all set... at
least until aphids get lawyers!

Good luck,

Charlie

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From: [email-masked] (SMITTOLA)
Date: 4 Oct 1996 00:13:05 -0400

>Sounds like you're on the right track.  You should hit 6.5 in >approx. 
>3 mos. 

>"If it ain't broke don't fix it."  And if what you're doing's >working,
>don't mess with it!  Once you achieve your target pH you >can titrate
>your KOH dosage down to a maintainence level, and you're >all set... at

>Charlie

Ha, Ha, or until lawyers get aphids.

Thanks Charlie for the info. I hope your right about the three months to
hit the 6.5 pH range. Our soil has a fairly high Cation Exchange Capacity
(CEC) of 28.28, I would guess this explains why the change is so slow.
This is a heavy clay loom type.

Is there a formula that can be used to calculate the amount of a base
material required to change the pH in a liquid feed system assuming the
CEC and pH of the media is known?

Thanks,

Steve Schmidt

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From: "Charles P. McCarthy" <[email-masked]>
Date: Thu, 03 Oct 1996 23:47:47 -0700

SMITTOLA wrote:
[edit]
> CEC and pH of the media is known? 

Steve,

My specialty is in clinical medicine so its best to take my advice with 
2 grains of salt and have your lawyer call me in the morning.

I think the CEC would be equivilent to buffer capacity, and you could
obviously calculate the amount of base equivilents required to produce a
target pH.  However, I think a problem arises in determining your
working volume.  This would be dependent on complex factors unique to
your soil, and could vary significantly over time even if you could
measure it reasonably accurately.  The chance of over shooting your
target pH with 
a resultant unknown effect on micropopulations could produce bigger
problems then can be forseen.  

I would tend to be conservative and continue on your current course of
treatment. If you wish to expedite matters, the simplest, safest, and
sanest approach might be to mulch, mulch, mulch and mulch.  This process
tends toward the acidic.  The hard part is deciding whom to make mulch
out of!

Best of luck always,

Charlie