Yikes! Sulfur lowered pH too much!

General Gardening
#21

Drano probably has some surfactants too, but I believe it is basically KOH.

#22

Before doing anything drastic I would get some cheap pH test strips and double check your pH. They are accurate to within 1-1.5 pH so it should be very apparent if your soil truly is as acid as the test shows.

Remember that your soil results are an average of just the spots you sampled. I’ve done my own soil pH testing and found a variability of up to 2 pH in samples taken 12" apart.

EDIT: If you send me 2-3 samples each 1/4 cup I would be willing to run a quick test for you thats accurate to within 0.5 pH

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#23

Thanks for the info!
I just put down some hydrated lime around each plant, worked it in as well as I could, and watered it well.
Then next day put some 0-0-60.

I wish I didn’t have to work around plants and could amend the whole bed. Now I will have pockets in the soil and will be hard to accurately test.

#24

Thanks for the offer! The ship has sailed I think though.
I feel the tests are accurate in this case only because I put a ridiculous amount of sulfur - I think as much as 50 pounds in maybe 100-200 square feet (what was I smoking?).

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#25

It would take 20 pounds of hardwood ashes to correct the ph in that soil. IMO, this would still be a good approach if the soil shows signs of being highly acid a few months from now. The problem I see is that amount of sulphur probably has not all reacted with the soil therefore your addition of lime will be countered by further acidification as the remaining sulphur is metabolized by bacteria. In other words, be prepared to take further action in a couple of months.

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#26

Anything that raises the pH rapidly runs the risk of over doing it in the opposite direction. Just use normal ag limestone. The lab that did the test should have recommended the proper rate. If they didn’t have another soil test done that will give you a recommendation. By the way I don’t doubt 3.3 at all. A big overdose of sulfur will do just that. I’ve done 3.3 on potted blueberries. Even they don’t like it that low.

If the limestone is finely ground and best of all rototilled in it will raise the pH plenty fast enough with little danger of over doing it.

#27

Thanks for the continued advice!

I agree it’s odd that the state lab did not include liming recommendations. I think it’s because I only specified ornamental “crop codes.”

I might contact them to get more info.

I agree that the sulfur (well, the microbes) may not be finished lowering the pH. I plan to add ag lime as a slow release mechanism to raise the pH.

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#28

So how much sulphur should I add to soil that hovers around pH 7.5?

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#29

There are some charts/guidelines out there on the web if you google it, if I remember from my research.

It varies based on the type of soil you have…clay versus loam versus sandy, etc.

Also keep in mind the pH-lowering effect can take months to materialize and may not be permanent.

#30

I’m definitely in clay. I’m planning to dose with done sulphuric acid for immediate effect while the sulphur has a chance to react with the bacteria.

I’ll see what Google turns up

#31

it’s best to test your soil. and wait for advise from the tester. CEC for example matters a lot. So does free calcium. Id advise against randomly dosing your soil with acids/sulfur. It can be quite damageing. Also better to start at 1/4th dose and slowly build up. than to overdose and try and fix that.

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#32

I definitely overdosed!! i should know better…not sure what got into me. :man_facepalming:

#33

You are right. Tell them the crop of interest or pick one they’re familiar with that needs similar pH and they can make a recommendation. Although they do need to know the CEC of your soil. So if that wasn’t determined it might require a retest.

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#34

Ohhh I was too cheap to spring for the CEC.
But I’ll ask.
The hydrated lime instructions indicated amount to raise pH by 1 point, though of course soil structure/composition has some influence on that. But i figured I would be close.

#35

Unfortunatly soils can have wildly different CEC and react wildly different to the same dose of lime/sulfur.

I would recomend to either use verry conservative doses and lower or raise over time. Or Do some proper measurements and maths. Or better yet outsource those measurements and maths to “the experts” by letting them test PH CEC and buffer PH

i would never trust “1 size fits all” advise from the lime bag. The manufacturer of that bag knows if he honestly gives the good advise of “test your soil before buying this product” a lot less product will be sold.

id trust the recomendations on the bag even less if they suggest a lineair dose (dose x for 1ph increase) since PH is on a logarithmic scale.

#36

2nd the soil test idea. pH can be increased with calcium, magnesium, or sulfur. Your soil is likely deficient different amounts of these minerals and can be corrected with different products and amounts of hi-cal vs dolemite lime, epsom salts, gypsum, aragonite, etc.

#37

Soil mineral nutrient deficiency is usualy not linked to PH.
You can have neutral or PH 6 soil thats deficient in all kinds of stuff, and soils of PH8 or PH 5 thats not dificient at all.

PH is basicaly a logaritmic measurement scale of [H+]
and should not be confused with soil nutrients. (think of PH more on the same line as soil compactnes structure etc, not as a nutrient)

Sulfur does not increase PH. It decreases the PH over time due to bacterial activity making sulfuric acid.

Magnesium depending on the source can or won’t increase PH. Usualy the effect is negilible small from just a magnesium fertilisation.

Epsom salts does not alter PH (or barely) since it’s a mix of sulfur (that lowes PH) and Magnesium (that increases it) they even eachother out.

TLDR
Don’t confuse a PH inbalance for a nutrient deficiency. Just get your soil tested and follow the advise from the test. Or if going the DIY route. Go verry slowly (years) and do the proper reading. Never randomly use PH decreasing or increasing substances.

#38

Because pH doesn’t have to be any precise number to serve my needs and is usually in flux here I tend to deal with the issue imprecisely to save money and time. I manage so many small orchards with such a wide range of soils that I’m a bit like a cook who can use a pinch or two of salt to get the desired results.

I used to go strictly by Cornell guidelines based on soil tests and one thing that was consistent was that the instructions on the bags was to use much less lime than the recs of Cornell to get to the specific pH I was reaching for.

Bags from different companies did the same thing so I presume they cover their butts by going very conservative.

#39

What might be a conservative dose on high CEC clay soil. might be an overdose on a low CEC soil.

Also there is a difference between a relativly tiny maintanance dose and dosing enough to change the PH a few points.

Respect for getting to a point where you can do it a bit more by “guestimating”. But i think if most less experianced people did it that way, they’d run into large problems.

#40

Not if they followed the directions on the packaging. All you really need to know is the relative texture of your soil and how much organic matter it contains to get more than an adequate sense of CEC.

No need to make things more complicated than they are- they are complicated enough.

Excessive liming is not something I have encountered in the hundreds of sites I’ve managed over the years. People consistently error on the side of caution, apparently. Probably because unlike sulfur it takes a lot of lime to alter a soil’s pH. Contractors save money by holding back adequate quantities to really transform the pH substantially. Soils excessively alkaline tend to have been affected by ocean influence around here, or by a limestone rich soil trucked in.