making soil acidic

February 18, 2011

not sure if anyone tried this and works... i dig a hole and put some peat moss and maybe even pour some vinegar in the hole, would that make the soil a bit acidic eventually?

i'm trying this method first without using chemical or sulfur based stuff.

Comments (67)

  • blazeaglory

    This works fine and is elemental sulfur and gypsum. I use it for my Citrus. My soil was Ph 7.7 when I first added it about 2 months ago, now my soil is a little above 7. I figure at this rate my soil should be where I need it by the end of the year. I might have to add more though. I also added and organic blend of food and bacteria so I think that is helping also. They do have directions for blueberries.

  • joe386

    Would LEYLANDII cuttings make the soil acidic i have just planted a hydrangea, im pretty new to gardening so any advice would be great

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  • TXEB

    Probably not - see link below.

    Do you know what your soil pH is currently? How about calcium level, water hardness and pH?

    Here is a link that might be useful: Pine Needles Cause Acid Soil - Fact or Fiction

  • blue_skink

    Has anyone heard of a powdered food supplement called MSM? It is a form of sulfur. If, as someone above stated, certain soil microbes use sulfur as a food source and the end result is sulfuric acid, which lowers the pH, then maybe this would work, too. Any opinions? Thx.

  • TXEB

    Sulfur, as in garden sulfur, can be used to lower soil pH. The mechanism is as you describe - soil microbes oxidize the sulfur and in the process with water it effectively becomes sulfuric acid. However, for it to work you can't have an excess of free lime present in the soil, and any irrigation water needs to be fairly low in carbonates.

  • blue_skink

    Thanks for your info, but how are we supposed to know if there is an excess of free lime or not? I know what the pH of the soil is (8) but that is not automatically due to lime, is it. There might actually be v. little lime in the soil. Is there some kind of home test one can do.

  • TXEB

    Home test ? No. You might check with local ag folks - they should have a good idea of what your soils are like. But if your native soil pH is 8, and your water is hard with calcium carbonate, then it is most likely your soil has excess free lime (meaning undissolved calcium carbonate) in the soil.

    This post was edited by TXEB on Tue, Sep 24, 13 at 18:25

  • toxcrusadr

    I would think a lab soil test that includes Ca would tell you that, if I understand TXEB correctly. Typically you get P, K, Ca and Mg results and the lab tells you whether they are low, OK or too high.

    MSM (methylsulfonylmethane) appears to be a dietary supplement claimed to help with arthritis and other health issues but not approved by FDA for any uses. It would likely be much more expensive than powdered elemental sulfur. Powdered sulfur works fine for pH adjustment.

  • TXEB

    blue skink - first, here is a reference from Colorado State University via their Master Gardner program that may help explain the issue of free lime, which is undissolved calcium carbonate in soil, a bit better.

    To get an idea of what is characteristic for your soil in MB, you can check out the Manitoba Soil Series here.

    I just looked at the Newdale Series, which is the official soil of the province, and it is described as a calcareous clay loam with a pH @ 7.2. Calcareous means mostly or partly composed of calcium carbonate, which translates to limestone or chalk. With your pH of 8, I suspect your soil has abundant free lime. It will be very difficult to effectively lower your soil pH in the near term. If you use irrigation water and it has an alkaline pH, then it will be extremely difficult.

    This post was edited by TXEB on Wed, Sep 25, 13 at 8:44

  • blue_skink

    I need P for my Tulips, that's what this is about. I thought just adding S would do the trick. I thought acidity=acidity, and it doesn't matter WHAT creates the acidity. But I looked on my latest soil test and it says "Sulphate - S: Excessive".

    Thank you kindly to the both of you for your links and help.

  • TXEB

    If you want to boost P levels while at the same time trying to lower pH you want to look for ammonium phosphate. It may be used as both an N and P component in various formulated fertilizers, or you can look for it as a stand alone and account for the N it brings. Some "starter" fertilizers use ammonium phosphate as a key component. You want to avoid, to the maximum extent possible, rock phosphate and triple phosphate.

    So, I'm curious, what else did your soil test tell you about your soil? Part of my interest is that your soil and mine in coastal SE TX likely have similar geophysical origins from about 75 million years ago.

  • blue_skink

    That is interesting that our soils, though located so far apart, have the same origins. However, Manitoba has several different soil zones, very different. This pocket where I live, not a large one, has sandy soil. Lots o' gravel pits near here.The soil in my garden was hauled (by me, from no deeper than 9") from wild, virgin land a short distance away from our house (1/4 mile), since my garden, near the house, was once a sod farm so the top soil was stripped.

    I didn't have our soil tested for Ca, Na or Mg for some reason. Wasn't interested at the time! Nor did I request Texture, but I can assure you it's Sandy soil. The results I have are:

    Nitrate Nitrogen: Marginal 14 ppm
    Phosphate: Deficient 4
    Potassium: Optimum 187
    Sulphate Sulfur: Excessive >20
    Iron: Optimum 206
    Copper: Optimum 1.5
    Zinc: Optimum 5.5
    Boron: Optimum 2.8
    Manganese: Optimum 20.8

    pH: 8
    Salinity: Okay - .6
    Organic matter - 27.9%

    So that is my sad story where soil is concerned!

    Wish I understood things better, e.g. why would ammonium phosphate be a good choice but not triple phosphate. Also, what if I want to avoid chemicals from a bag. I'm not rigid about this, though. Also, I have a bit of liquid phosphoric acid on hand (purchased for another reason) and wonder what you would think of me diluting this and using it to put into the tulip holes. To grow nice potatoes here, I put diluted vinegar into the planting holes and get very good crop, no insect problem, no scab in spite of soil being pH of 8!

    Tks for your interest in helping out and I'm curious as to your particular soil profile, too.

    Also, what is "free lime" as opposed to the Ca reading you get from a soil test?

  • TXEB

    We have similar origins, but the soils down here never saw any glacial action. The basis is both were covered by the Western Interior Seaway (use google), that included the Hudson Seaway in Canada. That's why the soils are calcareous - the now lands were former sea beds. Our typical soil Ca levels here are ~ 5,000 ppm near the surface, but subsoils can go into the 2-3% range. Typical pH is ~8. Our soils around here are mostly clay, but we have pockets that are sand pits. Still, the Ca levels run ~ 5000 ppm.

    Free lime is basically undissolved calcium carbonate in the soil (chalk/limestone). That's why the pH is high. With the abundance of free lime in the soils, there is little you can do to lower the pH in a lasting way. There's always more limestone already there.

    From your analysis three things jump out at me. One is the iron level, which I suspect is a typo (20.6 ?). The second is your micros (iron, zinc, copper, manganese) are generally high. Third is your organic matter is out of sight -- 27.9%. Is that right? If you raided the woodlands for soil that might explain a lot of that. Have you added any amendments, manure or compost of any kind?

    The reason I suggest ammonium phosphate is because it is a Ca free source of P. You most likely already have a lot of Ca. On calcareous soils the frequent reason for low P is that the dominant form of P in soils, orthophosphate, combines with Ca to form insoluble complexes headed for apatitie. It is a very slow process, but nonetheless it occurs. Over a period of ~ 9 years my base soil P levels have gone from excessive at ~100 ppm to 10 ppm. The conversion is aided by the fact that my irrigation water (municipal water) contains about 100 ppm of calcium carbonate. The last thing I want to add to my soil is more calcium, especially if I want to raise P levels. Ammonium phosphate is a preferred route. It also is acidifying, which helps.

    Phosphoric acid would work too, and would do even better on the acidification. But the pure stuff (85%) takes a lot of dilution and well controlled application. It does have the added benefit of a stronger and more lasting pH reduction.

    BTW, to me sulfur at 20 ppm is high, but mine is ~ 40 ppm, and is not characterized as "excessive". I believe you can relax about the S.

  • florauk

    blue_skink - I know nothing whatever about soils but if you are just concerned about your tulips the soil is not massively important since the bulbs you buy already have all the nutrition in them which the tulips need to flower. You could even grow them in plain water if need be. Only if tulips perennialise in your garden and thus need to build up flowers for next year is the soil of much importance. Even then they tolerate a wide range of soils and are not particularly fussy.

  • blue_skink

    Hello, TX. Thanks for all your interesting info! Yes, Iron reading should have been 206. You are pretty smart about these things. You can even see my typing errors!

    You say that my micros are generally "high", but the lab classified their quantities as "optimum".

    Thanx for your opinion on the sulfur. They are talking about Sulphate, right? Maybe there are other forms of S in soils?

    I raided an area on our property that is fairly near a forest. Is all that org. matter a bad thing? I wondered about that, because people who have low org. matter knock themselves out trying to fluff theirs up!

    So, to make a long story short - it's not about absolute amts of P or S, but, rather, free Ca??

    Regarding watering: I use rain water from the barrel for as long as I can but then but by around August or so there tends to not always be enough rain.

    I add a bit of chicken manure mixed with straw that has partly broken down outdoors during the spring/fall/winter. Also partly decomposed kitchen wastes that break down pretty quick in the spring.

    Finished compost in huge amts is supposed to solve everything, but I wonder...

    Oh, one more thing. I read FWIW that no soil anywhere on earth is perfect for agriculture or gardening. In one way or another, they are out of balance. However, whoever said that doesn't consider that not all crops want the same things.

    I know nothing about soils but I could read and discuss it all day in the hopes of learnig about my own. So glad you and others are here to help out.

    Flora - I have tried to grow Tulips in the past. They'd do good for the first year, as you mention, because the bulb has food in it. But I want them to keep on going. That is why I'm concerned about acidity, Phosphorus, etc. Thank you so much for your info.

  • florauk

    Tulips are hard to keep going in many areas. I don't think it has a lot to do with soil but more to do with the type of tulip and your climate. Failure of tulips to return is largely a matter of giving them cold winters, hot dry summers and sharp drainage. Obviously you will get sufficient winter chill, so that won't be an issue. The old fashioned Darwins and some of the species are the most dependable. Aside from your soil discussion here you might want to post your tulip query on the Bulb Forum here on GW. Notice that there is no mention of acidity in this article.

    Here is a link that might be useful: Getting your tulips to come back.

  • blue_skink

    Thanks so much for the link! I think maybe I was trying to grow the wrong varieties. Yes, it's true, our climate here is darn near perfect - cold winters, hot dry summers. And I strive to provide good drainage.

    Still, I don't like our superalkaline soil. Geeeze, I could make soap out of it. There is something magical, too, about compost. It seems to have a balancing effect on too-acid or too-alkaline soil.

  • TXEB

    blue skink - tulips aside, my characterization of your micros as high is based upon current TAMU critical levels for those nutrients. That may well be an inappropriate view for your soils in your environment. The fact is the values determined via analysis are quite dependent upon the method employed, and can vary a good bit between different methodologies. Whether levels are low or high should be based correlation studies between plant response and the nutrient levels determined by specific methods (often called calibration). So long as your analysis was done by a lab using method suitable for your soils and the interpretation is based upon matching plant calibration studies, stick with that.

    BTW - willing to share who did the analysis?

    On S- the most common form in aerobic soils is sulfate. But if the method of analysis is based upon ICP, it will typically include other forms of S that were extracted along with sulfate, including different inorganic forms or organically bound S. The number on your soil report should represent the amount of elemental S accounted for by the method of analysis.

    On P - the same is true for P as S. The dominant form in soil is orthophosphate. But their are other inorganic forms as well as organically bound P. Depending upon analytical method what is seen may be orthophosphate or may include those other forms.

    The play between Ca and P is that in calcareous soils Ca will, over time, sequester phosphate by combining with it into intractable forms that will not show up in the analysis, nor will they contribute to either Ca or P available nutrient levels for plants. For both Ca and P those complexes are considered "fixed" forms of the nutrient element. What is important for plant nutrition is that which will be available for plant consumption. Soil test methods are developed to reflect the levels in soils that plants can access, not the total elemental content of the soil. I suspect you have way more P in your soil than your analysis shows. That extra, in principle, will not be available for plant nutrition. That's the fixed P.

    This post was edited by TXEB on Fri, Sep 27, 13 at 9:05

  • blue_skink

    "Soil test methods are developed to reflect the levels in soils that plants can access, not the total elemental content of the soil."

    I'm glad you mentioned the above. I would never have considered this. It would be interesting to know, tho, just how much P my soil has, just for the hellofit. They say that P is the most underrepresented agricultural mineral in the world, that there's few places that have a lot, free lime content notwithstanding.

    I had my tests done at Norwest Labs in western Cda. I think they are pretty good, they came highly recommended to me.

  • TXEB

    "It would be interesting to know, tho, just how much P my soil has, just for the hellofit."

    You can get that done, and with the right lab it's not all that expensive. If you could figure out a way to get a sample to NY (lot's of hoops to jump through importing soil into the U.S.), Cornell offers two versions of a Total Elemental Analysis. The time-honored traditional method goes for $35 - includes determination of total Al, As, B, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, S, Se, Sr, Ti, V, and Zn. A newer version of the test goes for $17.

    Here's a link to the Cornell Soil Analysis submission form. Scroll down on the second page to "Total Elemental Analysis/Heavy Metal Screening", see tests 2020 or 2021.

    You might check with the lab that did your work to see if they offer something comparable for a reasonable fee.

    Now the question I always asked folks who came to me saying they wanted to know if they had any of X in their soil/water/food/etc. ... What will you do with the data? Think through it - what if the answer is A, or B or C - what would you do? How does it help you to know? Is there anything you would or will do as a result of knowing? Does an answer, at any level, one way or the other, lead to action in any way, on your part? It's generally a good idea to know what you will do with the result before you ask for the test.

    Here is a link that might be useful: Cornell Soil Testing Submission Form

  • vinegarlol

    OP, Vinegar IS a chemical

  • gardenshine

    lol, yes .... it is! I was wondering if anyone was going to say it out loud.

    Vinegar CH3COOH. And chemicals from a bag????? hellyeah....... elemental organic sulfur (S). And you can get organic NPK from a bag too and yes, they are chemicals. So is water (H2O). Calcium (CA) Ammonium Sulfate (NH4) ..... etc etc

  • toxcrusadr

    Someone DID say it, back in 2011 when the original post was made. :-]

    And of course it is. It's a little amusing to talk about changing soil pH without using chemistry, when the whole concept is based on chemistry.

    Since we're making corrections, there are two other issues in this thread. One is the post by ceth_k that 'compost raises soil pH'. Actually it tends to make it more neutral, if it is very far away from neutral in either direction.

    The other is that someone posted that watering with alkaline water is going to be a problem (which is true) and to check with an ag extension agent about local water. That may work but it all depends on where your water comes from. If it's public water, the water supplier has that info and it's often available online. If it's your own well, someone may be able to take a guess, if you know your well depth and what formation it's completed in. But the only real way to know for sure is to test it.

  • sam (SF bay, 10a / Sunset 16)

    This thread is a bit old, but since this is the relevant topic, i am posting here. What is wrong with supplying water that is mildly acidic, to all the plants ? I got the idea of mixing vinegar from gardengal40 in another thread. So, why not use a "hose end sprayer" from home depot, and fill it up with household vinegar and set the dial to disperse it at rate of 1 TBSP per gallon ? That should produce water in the range of 5.0 to 6.0 depending on your tap water pH. Over time, this should slowly acidify a alkaline soil too (is my guess). This may be a much cheaper and less labor intensive than mixing sulfur tilled into soil. The soil around the plants can be kept at desired acidic levels, simply using water. Monitoring soil pH would be needed with this approach, perhaps once in 6 to 12 months, depending on the rate at which you are supplying acidic water to the area. The acidity won't last long, because the soil around the plant has lot more buffered pH and will try to revert to its natural pH level. But over time, this may impact a wider area around the plants that are getting watered this way. Comments please ?

  • sam (SF bay, 10a / Sunset 16)

    BTW, another factor to keep in mind while using the above technique ...... We can not drastically vary from existing soil pH, for fear of killing the soil microbes with sudden changes. My guess would be that microbes can tolerate rain water even if the soil pH is about 8.0. Since rain water is around pH 5.6 , a maximum pH change of 2.0 at a given time is better while watering with above method.

  • blue_skink

    Would rain water have a pH of around 5.6 everywhere?

  • gardengal48 (PNW Z8/9)

    I would not rely on just water - either treated tap water or naturally occurring acidic rainfall - to have a significant effect on altering soil pH. Will certainly help to neutralize alkaline water sources and can laso help to delay a buffering effect from sulfurized soil. It will certainly not lower a soil pH anywhere close to 2 pH points at any given time.......unless it is a flood!!

    And no, the pH of rainfall can vary widely. It tends to be more acidic closer to large metropolitan areas where there are higher levels of air pollution.

  • sam (SF bay, 10a / Sunset 16)

    The 2 pH points i was referring to is the difference between the soil pH, and the water pH (prepared using vinegar). The process of watering will change the soil pH slowly and steadily over time (is the expectation). For the sake of completeness, i want to include in this thread 3 articles that i found useful (when someone wants to resort to Sulfur for acidifying the soil):


  • blue_skink

    Plants grown in soil with a lot of organic matter have healthier roots. They’re able to extract enough nutrients from the soil even when the pH isn’t optimal.

    In a healthy soil with adequate organic matter, changing soil pH may not be necessary, because plants continue to grow at pH levels that would stunt growth in leaner soils.

    When you increase soil organic matter, you’re not really changing soil pH, you’re increasing your plants’ tolerance for acidic or alkaline conditions.


    Bingo. That's what someone told me a long time ago. With our crazy high alkaline soil, I still manage to grow vegetables that want more acidity. I guess it's because I dump quite a bit of kitchen slops (organic waste) right into the garden in the fall and all winter.

    If agriculture were dependent on perfect pH level, we would have died out a long time ago. There's a reason that people were attracted to rich, fluffy, high-organic matter soil right from Day One.

    The high-organic-matter soil I first placed into my garden 20 years ago produced lovely crops but over the years the organic matter has become depleted and I have had to work hard to bring the level up with all those kitchen wastes.

    @Sam. Many thanx for the 3 articles!

  • gardengal48 (PNW Z8/9)

    There are a few issues here that could benefit from some clarification. Most plants have a range of pH levels they will tolerate. Often not a very wide range but a range nonetheless and some quite a bot wider than one woud expect. But the vast majority of plants would prefer a slightly acidic soil pH as that is where the largest range of nutrients become available and accessible....somewhere between 6.0-7.0

    And no amount of organic matter will help a plant that prefers acidic conditions - like any of the Ericaceae - thrive in an alkaline pH soil. It all boils down to a basic understanding of soil science, chemistry and plant morphology. Organic matter can do a lot of things in the soil, including a slight modification of pH, as well as providing some nutrient input. But how accessible those nutrients will be to the plants still depends on the soil pH.....there is really no way around that.

  • toxcrusadr

    A bit of a tangent but I just wanted to point out that rainwater, having virtually no minerals, has no buffering capacity. So its pH will change very easily. If the soil pH is 8 and rainwater is 6, it's not going to suddenly be pH 7 when it rains. It would be much closer to the soil pH before it rained. Hard alkaline tapwater has much more buffering capacity which means it takes a significant amount of acid to change its pH.

  • blue_skink

    I don't know much about how placing kitchen wastes right in the garden beds works. If my slops have a fair bit of lemon & other citrus peels with a bit of juice left in them, after I reamed them out, would that produce more acidity in the soil or not?

    A few months after I place the slops onto the beds, then cover them with some soil, I see tons of earth worms when I dig into the soil slightly. Is that a bad, good, or neutral sign?

  • gardengal48 (PNW Z8/9)

    "would that produce more acidity in the soil or not?"

    Not enough to make any difference. And as they decompose, they will lose any acidity.

    The worms are present due to the organic matter in the soil. They tend to be one of the more visible signs of the biological activity that always accelerates with applications of OM.

  • toxcrusadr

    Not only is the amount minimal, but the kinds of acids in citrus are organic acids, which are not only relatively weak, but also biodegradable. As opposed to mineral acids (hydrochloric, sulfuric, nitric etc.) which are both stronger acids and more permanent.

    Composting (including breakdown of buried compostables) will always bring the pH of ingredients toward a neutral result, too.

  • blue_skink

    @garden gal & toxcrusadr. Thanks for your info. I think I get it now. :)

  • sam (SF bay, 10a / Sunset 16)

    Over the past 5 days, i have watered my budding plants (about 6 to 10 " height various species) with acidic water. Before that i was using tap water, which i measures at a pH of 7.7 (it varies over the year and is higher in other seasons). I bought a hose end sprayer from HD, and filled it with vinegar + tap water. The pH of this was around 5.0. Noteworthy here is that the data i found about using vinegar to change pH did not work for my tapwater. My tap water had much more buffering capacity and hence that information was completely useless. I had to measure many times, to find out the pH of mixture that comes out of the hose end sprayer. Also noteworthy is that the hose end sprayers have gross problems and the cheap ones do not output properly in all different settings.

    With this change, the hose end sprayer output my tap water at 6.5 and i used this about 4 or 4 days to water my young plants. There was a noticeable difference in the plants within 2 times. Obviously they were much happier to get 6.5 water rather than 7.7 pH and could use the store bought potting mix at a better value. I confirmed with Kellog's that their potting mixes have pH in the range of 6.7 to 7.2 and it varies.

    I plan to continue this watering technique for my potted plants, since tap water will not use the full extent of fertilizers present in potting mix.

  • blue_skink

    V. interesting! I don't know what's involved in measuring the acidity of water. I just know that when I grew potatoes in the past I would put 1 cup of regular vinegar in an ordinary sized watering can, mix it up, and use this to water the newly planted seed and then later on, too. I had the best potatoes in our 8.0 pH soil. No scab, no bugs. Good crop all around. I did not use any fertilizer, either.

    I would not trust those hose end sprayers. I would think there's too many variables.

  • toxcrusadr

    >>Noteworthy here is that the data i found about using vinegar to change pH did not work for my tapwater. My tap water had much more buffering capacity and hence that information was completely useless.

    I'm not at all surprised and the linked info should be more of a general guide or starting point rather than a recipe that works everywhere. Tap water varies quite a bit depending on what kind of rocks it's being pumped out of. Hardness is not the same as alkalinity, so two people might have 'hard' water but they could vary quite a bit in what is making them hard, and one may have much more alkalinity than the other.

    Total alkalinity does not correlate precisely with pH either. pH is directly proportional to free H+ (any by extension, OH-). Other alkaline ions (carbonate and bicarbonate) do the buffering and require a non-linear addition of acid to change the pH. Alkalinity is the sum of the three.

    Hardness is related to Mg and Ca content. Those cations could be associated with carbonates, OR with sulfate, or even chloride, as anions. These all behave differently (or not at all) when interacting with acid.

    The combinations of concentrations of all these ions are endless and that's why your results won't work perfectly for anyone else.

  • blue_skink

    So many things I didn't know. Thanks for all the info.

  • sam (SF bay, 10a / Sunset 16)

    >> ".....Noteworthy here is that the data i found about using vinegar to change pH did not work for my tapwater. My tap water had much more buffering capacity and hence that information was completely useless. "

    I have to retract my statement above. I can not say it was completely useless, but was a good guide to start with, as toxcrusader pointed out. My results were similar to that, but not exactly what was described in the link i gave about "Adjusting pH with vinegar". Thanks to my hose end sprayer, i have been watering all my potted plants with my tap water at a pH of 6.35 (adjusted with vinegar). I am also watering my yard trees with this water, rather than tap water (at average pH 7.7 in my area). Potted plants seem to be doing ok. I did not know much about rose plants, and my roses flowers died ; hence i suspect that roses do not like acidic water. (Not sure, since i am yet to reverse the water for roses).

  • toxcrusadr

    Whoever posted that page about pH adjustment should have put in a big disclaimer saying 'your mileage may vary.' :-]

    If you were to Google "ideal pH for roses" there are numerous links suggesting pH 6-7. If your roses aren't happy, it could be a lot of things besides pH. Or, the surprise shift from 7.7 to 6.35. I'm no rose expert by any stretch!

  • blue_skink

    One thing I don't grasp: all the superficial (non scientific) articles on soil that I read automatically assume that acidic soil (I don't mean as bad as stomach acid, but somewhat less than 6.0) is some kind of calamity, but alkaline soil, say, 7.5, is not.

  • sam (SF bay, 10a / Sunset 16)

    Blue - the general consensus i have read is that pH below 6.0 is not acceptable to most vegetable / fruit plants (except the varieties that love acidic soil like blueberries etc.) Most vegetables seem to thrive between 6.2 and 7.2 range. This is why all potting mixes tend towards neutral pH area. Note that 7.0 is the neutral, and so it makes sense that 7.5 will be tolerated, but not a wide 1.0 variation to 6.0 and below. If i were to venture, i would guess most plants would thrive within + / - 0.5 from their ideal pH (for each specific plant , if there is such a thing).

    tox - There was no change in the conditions other than the following that i can think of...

    1. I did not water the plant for about a week - but my roses flowers will not die en mass in the past (just because of watering issue).
    2. I was watering the rose plant for few days with my vinegar + water solution. It has only seen soil pH above 8.0 and only seen tap water at 7.75 until then. This was sudden change after few years of growth.
    3. The temperature was above 90 degrees for 3 or 4 days straight. I think i did water couple of days during that time. This was 1 week ago.
    4. I moved a tomato plant next to it, about 3 feet away from it roughly. This tomato plant had all the leaves infected with some fungus that turned the leaves black and leaves were curled up. This sick tomato plant was next to the roses for about a week. I have to check if the leaves of rose are affected, since i only noticed the 10 dead flowers (en mass, within 2 day period).

  • toxcrusadr

    My family lives in New Mexico where it's fairly arid and the soil has a fair amount of limestone from the adjacent mountains which used to be sea bottom. So the soil pH is almost 8. With copious additions of compost, vegetables and fruit grow just fine (if you water the crap out of them, that is!). Bottom line is that organic matter helps to moderate the effects of pH.

  • sam (SF bay, 10a / Sunset 16)

    @toxcrusadr - I am curious. What do you think will be the chemical breakdown of vinegar (part of the water), once it gets into the ground ? How does it break down and what chemical reactions can we expect in an alkaline clay soil (like SF bay area) ? I am wondering if the chemical reactions out of vinegar would leave some residue that has long lasting effect on the soil.

  • armoured

    I'll take a stab at this although not a chemist. Acetic acid is just carbon, hydrogen and oxygen, with free hydrogen protons making it acidic. So while it could react in many ways and be bound up with whatever is making the soil alkaline, there is unlikely to be much residue - there would be a tendency for the breakdown to be biological digestion and be volatile, perhaps just being used by organisms to make water. Now there could be reactions that would retain the neutralizing factor, depending on what is there, probably a high likelihood of it just having a minor temporary effect. Organic materials - sugars, carbohydrates, etc - would also break down with acids being created and destroyed by digestion, but more slowly.

    Again, this is my own analysis with no better than high school chem, but I think may be roughly correct about why compost would have a neutralizing effect for longer than vinegar. Happy to be corrected by those with actual knowledge.

  • toxcrusadr

    That's a pretty good analysis in my estimation. Acetate would be chewed up by microbes to CO2 and water.

  • armoured

    Makes me feel a bit better about my high school chemistry.)

    Should perhaps have been explicit that by volatile above just meant that a lot of the products / by products may likely just offgas as water vapour, CO2, or other intermediates of biological breakdown, ie not much longterm residue per the question.

  • sam (SF bay, 10a / Sunset 16)

    Something that might be useful info to add to this thread :
    I prepared a pH 2.96 using vinegar (6%) 14 TSP + tap water at pH 7.73 and noticed that the pH drifted to 2.85 area, when i let it sit for about 30 minutes (open to air). I am guessing that the stirring i did not fully complete the chemical reactions and it takes time to stabilze. So, having a pH meter is enormous help if you are doing this technique to water your plants. I also found out that you need to have a high quality hose end sprayer, because the cheap one from HD that i got would mix the solution at ratios that had nothing to do with the markings given on top of it. You may set it to mix 4 TSP to gallon, but it will mix up lot more than what you would expect.

  • blue_skink

    @Sam. You could use the low tech version. It is called a watering can + measuring cup. Well, that is what I do, anyway.

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