Yikes! Sulfur lowered pH too much!

I got a little careless applying elemental sulfur to some flowerbeds last year.
My pH just came back at 3.29!!! :open_mouth:

Planning to use hydrated lime regardless, but my question is:

Can I safely and effectively use a baking soda solution to get a quick hit neutralization?
I just planted some new shrubs prior to the test so I want to get them some help ASAP

Help! :sob:
PS no, I can’t put in blueberries instead :rofl:

Baking soda has too much sodium but you can use potassium bicarbonate.

Isn’t your soil super high in calcium already? Can you just buy magnesium carbonate? Or wood ashes

(I thought you had a test last year with a way higher calcium? Also is it possible a peice of sulfur got in with your soil sample? You have a decent amount of buffer so going to 3.3 would be a crazy amount of extra sulfur you added)


Hey! Good memory - yes my native soil in the back is high calcium and high pH but this is in two flower beds in front of the house.
I tillled in a bunch of sulfur and just went too heavy on it.
Thanks for the info On baking soda.
I was concerned about sodium, which is partly why I wanted some help. Thanks again!

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@RichardRoundTree oh - I read about potassium bicarbonate but is that readily available?
I did a search earlier and seemed like everything was lab oriented

if never seen such low PH in soil.

If im not mistaken elemental sulfur works because soil life (bacteria) convert it to sulfuric acid. Since sulfuric acid is quite water soluable. And most high PH calcium compounds are not. Might this trow off your measurement?

at your PH of 3.3 your ultra acidic. on the lower end scale of orange juice, nearing vinegar. Is your soil really that acidic?


This is my state soil lab results. I trust them.
I was careful to take multiple soil samples.

I put pounds and pounds of sulfur in a small area. It has been a year, so time enough for the microbes to convert to acid.

I observed some issues with plants in those beds and realized I probably overdid the sulfur.
So I got it tested and it confirmed my fears.

Would KOH work? It is fairly soluble, basic, and only adds potassium.

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It probably would but I need something ASAP. I don’t see any commercially available KOH on Google.
At the co-op now getting hydrated lime and muriate of potash for the K needs.

It is sold as a soap making supply. I bought some on Amazon years ago.

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Ah ok! I figured maybe there was a brand name or something.
Thank you!
Co-op was out of lime! (In 5 pound bags)

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It is sometimes called caustic potash.

What is your target pH? Do you have the option of digging up the soil?

No, the best I can do is plug it and backfill with some lime, etc and just work it into the top. Or water with a basic solution.
6 would be fine I guess.

Potassium bicarbonate is sold as a natural ph up earth juice has it as natural up. I dunno about using the hydrated lime but a bunch of dolomite watered in should neutralize it. The koh should do the same as well as wood ashes soaked in real good.

I would be careful raising it too fast also but you definitely want to neutralize that.

The potassium bicarbonate that was recommended is highly soluble and has the advantage that it would react quickly to raise the pH. I just noticed on you report that the buffer value for you soil was measured at 6.9. In a sense this would be the natural pH range of your soil. So as you approach 6.9 pH is would be somewhat harder and harder (require more and more) potassium bicarbonate to continue to raise the pH. The report did not contain a CEC (cation exchange capacity) value which one might think of a as measure of the strength of the buffer. Clays like kaolin, fullers earth and even vermiculite would help also bring the pH back up and provide some additional buffering capacity.


NJpete’s reply is great!

i personally would be a bit worried. Seems like you overdid sulfur, and are now quickly trying to fix it in some more unusual (but not unheard of) ways. Usualy nothing good happens fast PH wise.

I’m a bit afraid you might overdo raising the PH now.

Also both substances that raise or lower PH are really acid or caustic. And react readily with all sorts of things, like plant roots for exampel. So using such substances on existing plants that are in to acid soil, won’t be liked by them.

I would remove the perrenial plants you want to keep. Plant them in pots or somewhere temporary. And take your time slowly adjusting the PH. You could sow some temporary annuals as sacraficial testers, and to make it look nice.

Think of it like pooring kerosine and lighting it over a frozen plant thats frost intolerant. You would hope to much cold and to much heat would even out. But practicaly thats not always the case. While the fire and ice “fight it out” the plants caught in the middle. And if you use to much kerosine your plant gets to hot and starts burning!

ideally you’d know your CEC (Cation Exchange Capacity) and use that to calculate how much “substance” you’d need to raise your PH. And slowly add that. prefurable after you temporarely removed your perenials.

i might be overreacting though. I have no experiance with 3.3 PH soils.

The one secret I’ve learned that might be useful knowledge to you is that plants can sometimes get what they need from limited access to soil that provides it. The literature frequently suggests, for instance, that blueberries only thrive in a pH below about 5.5 but, in fact, they only need a portion of their soil at that pH. I discovered that by accident because my blueberry plants were thriving at about 6.5 (I thought) and I often boasted about it and was dismissed as an idiot by some, including a professor at the University of New Hampshire who assumed I’d mistested my soil. In a way he was correct. I had failed to test the pH of the soil 12" down where the pH turned out to be about 5.6 and the roots growing there are apparently able to extract all the iron they needed for the plants to thrive.

I later learned that famed horticultural researcher Carl Whitcomb had done an experiment with pin oaks that also have a problem getting enough iron in soil with a pH above 5.5 or so. He discovered that by broadcasting sulfur on the surface the trees would green up very quickly even though the soil had yet to alter it’s pH beyond the very surface.

Your problem is too low a pH. but you may not have to entirely transform your soil to grow plants in it, especially if you spread an inch or two of a near neutral humus topped with mulch on the surface instead of trying to transform all of it. The mulch will allow feeder roots to come right to the surface of your soil and help keep it moist and moderate temperatures- when the more neutral compost dries it cannot serve your plants.

Yards for mason and landscape contractors around here often sell compost they make from lawn clippings, leaves and woodchips brought by landscapers, some towns even have if for free. The compost can have has a pH as high as 7.5, is usually near neutral, and if you could find some of that you might solve your problem without instantly transforming all your soil.

If you annually mulch the soil it might sustain very good growth for the plants you have there while it gradually de-acidifies.


alan makes some excelent points.

And i would be really intrested to run an experiment someday. grow 2 blueberry’s or somthing like that. 1 in a pot with acid soil, 1 in a pot with alkaline soil. And graft the 2 plants together. 1 plant 2 rootsystems. And see if it goes well. Or maybe graft a nursebranch over from the acid 1 to the other to see if it “shares” the needed nutrients.

Or better yet, have 1 plant in somthing like perlite. and split up the rootsystem 2 ways 1 to acid 1 to alkaline.

since most literature states the mechanisem behind soil PH and how it affects plants is mainly the nutrient takeup. It makes sense that only a few roots in the right PH can takup enough for the whole plant.

im also curious if the bacteria that make the sulfuric acid have higher populations near roots. The decreased PH effect might even be localised near rootmasses. Since most root exudates feed loads of bacteria.

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You seem to have the mind of a research scientist. In the U.S. it generally is not considered impolite to ask a person what they do for a living, but you are from the Netherlands, so I won’t ask :wink:


Thanks folks for the robust discussion and assistance!
My only reason for wanting a “quick” solution is to avoid having the acidic soil “kill” the $200 of shrubbery I just planted.
I generally do not look for quick fixes in gardening. :grin:

@alan i have read a whitxomb paper, probably the one you referenced, about localized soil pH. It makes sense to me.
In fact, the half dead shrubs I just pulled out which had been there over a year had almost zero root growth outside of the original root ball EXCEPT downward. Presumably they were reaching for the unamended, less acidic soil. This speaks to your point. The plants weren’t dead but the nutrient issues I believe caused hypersensitivity to the 10 degree weather we had in February and killed them back about halfway.

I think I will just apply some hydrated lime per the label and maybe add some compost. I might do some plugging like mentioned in the Whitcomb paper.