505zoom
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Posts: 31
Joined: Fri Jun 13, 2008 4:06 am
Location: Albuquerque, NM

Lowering soil PH mid-season

Should I even attempt this? The soil PH is too high (7.5 - 8ish) in my veggie garden, and way too high for my blueberry bush. I know that I can work on it over the winter (and I will), but is there anything I can do immediately to lower the PH without hurting the growing plants?

cynthia_h
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Posts: 7501
Joined: Tue May 06, 2008 11:02 pm
Location: El Cerrito, CA

Funny you should ask. I just got home from a round of errands, one of which was purchasing a bag of aluminum sulfate (4-lb or so bag was the smallest amount available!) to change the pH around my MIL's two hydrangeas and make them turn blue again. They were planted August/September 2007 by a landscaper with an off-again, on-again "automated" watering system. The poor things have survived on winter rain and my approx. once-monthly drownings, but their flowers are a sickly white.

On the aluminum sulfate bag are printed directions for lowering the pH of soils in general as well as specific instrux for hydrangea coloring.

Maybe a local garden store can set you up with some of this. I'd use it very sparingly, though, since it seems to be a concentrated product, and would also support the blueberries with an acidic compost containing pine needles.

Cynthia H.
USDA Zone 9, Sunset Zone 17

505zoom
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Posts: 31
Joined: Fri Jun 13, 2008 4:06 am
Location: Albuquerque, NM

Oh wow, for some reason I thought that using the aluminum sulfate could only be done months prior to planting. I was thinking it would make my peppers taste like a coke can. :D

I will look into this more now, thanks for the tip.

If anyone else has any methods, please share. It's always nice to have variety. :wink:

505zoom
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Posts: 31
Joined: Fri Jun 13, 2008 4:06 am
Location: Albuquerque, NM

Well I was nervous about adding any aluminum to my edibles, and turns out for good reason. Just called my county extension and they put me on the line with one of their "master gardeners". She admitted that she did not know the answer, and took down my number to call me back. After some research, she informed me that the aluminum sulfate is not recommended in veggie gardens while the plants are growing. She said to instead try pure powdered sulfur for the long term, and to use a cup of vinegar per gallon of water to bring it down for now.

So, if anyone has experience with using vinegar in this way and has any tips or advice, I would appreciate to hear them. I would hate to use too much and hurt the plants, but I would like to use enough to get a result. Not sure how frequently I should apply the vinegar to bring the PH down about a point or so and keep it there for the rest of the season.

MaineDesigner
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Joined: Thu Nov 09, 2006 4:17 pm
Location: Midcoast Maine, Zone 5b

Aluminum sulfate is the wrong answer for a bunch of reasons but ferrous (iron) sulfate is also quick acting, however, read on. I don't think most vegetables aren't likely to have much problem with a 7.5 (or even 8.0) pH - most plants are able to adapt to a fairly wide range of pH even if it isn't "optimal". The blueberries are an exception and are not going to be happy at 7.5 or 8.0 - they want a pH around 5.0. I've never tried to knock down pH to anywhere near that extent during the growing season and I suspect that trying to do is is likely to hurt the blueberries at least as much as the high pH. Blueberries require a symbiotic relationship with soil fungi to absorb minerals.
You may also find that your soil chemistry will quickly buffer the pH back to neutral or alkaline no matter what you use or how much. Sometimes you can build a raised bed out of soil "designed" to be acidic and garden on top of the existing soil, I suspect this may be your best option for the blueberries.

505zoom
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Posts: 31
Joined: Fri Jun 13, 2008 4:06 am
Location: Albuquerque, NM

Thanks for the advice MD. Good stuff there. Didn't think about iron sulfate... been trying to think of different ways to get a little more iron in my diet too. :lol: I will look into that more tomorrow.

I watered the gardens with the 1 cup of vinegar per gallon this evening. Interesting thing, in the 2 spots where the peppers aren't doing as good as the rest, the soil actually "foamed" in reaction to the vinegar. :shock: So I took a quick soil sample from those two spots before the vinegar could settle in deep, got readings in the high 8's. :?

I'll try the vinegar waterings for this week, gradually tapering it off, and do the soil tests again over the weekend.

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