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hill_gardener

Quicklime

Hill_Gardener
9 years ago

I was wondering if anyone could help me - I accidentally added quicklime to my borders in autumn, probably at the rate of half a small glass per sq/m. I recently put in some plants, which are currently looking rather yellow and dried out. The position is cold and exposed so I had thought this might be due to recent frosts, but these have now passed and the plants are failing to put out new leaves. Perennials added last year are also looking fairly anemic and washed out (I will put up some photos if anybody is interested).

The lime came from an opened bag stored in a damp shed for about 10 years. I have read that quicklime is not stable and, once exposed to carbon dioxide in the air, returns to calcium carbonate, but I have no idea if this has occurred, and the soil still feels caustic to the touch. It was dug in well to a spade's depth. The soil appears 'flocullated' (if that's a word!) and drier than usual.

I am now panicking at the idea of removing 40 plants from a newly planted border and replacing all the soil. Does anyone have any idea how, or if, I could get around this?

A friend who understands chemistry much better than me thought carbonic acid might reduce the quicklime, now possibly slaked lime (calcium hydroxide) since it has had water added to it, possibly in the form of sparkling water, though a powdered form if available would be more economical.

All ideas welcomed

Thanks

Hill_Gardener

Comments (18)

  • toxcrusadr
    9 years ago

    You need to check the pH of the soil asap. If you have a soil lab around, i.e. County Ag Extension, you can take them a sample. Store bought pH meters are not that great, but if you use one, make a 50/50 slurry of soil and distilled (!) water, let sit for a few minutes then test.

    If pH can be raised, it can be lowered too. Sulfur takes time to work, so that's probably out. Perhaps diluted vinegar or aluminum sulfate (which you can buy at nurseries for use on blueberries, etc.). FIRST you have to find out what the pH is and go from there, or you won't know how much to add.

  • Slimy_Okra
    9 years ago

    Yes, that flocculation is a classic sign of excess calcium.

    The calcium hydroxide would have converted to calcium carbonate by now, bringing the pH down from 11-12 to 8-9. That is still too alkaline for most plants.

    As the above poster suggested, get a soil test done. The quickest way to reverse the damage is to dissolve iron sulfate in water and apply it to the soil daily. How much iron sulfate to apply depends on the weight of lime you added.

    Assuming that your "small glass" is 250 ml, you added about 125 ml, which is about 250 to 300 grams of calcium carbonate equivalent, per square meter. That means you have to add about 700 to 900 grams of iron sulfate heptahydrate* per square meter. Apply 150 grams daily for five days, dissolving it in at least 20 L of water per application per square meter.

    *The heptahydrate form is the most commonly sold in garden supply stores. If you end up getting the monohydrate or anhydrous form of iron sulfate, decrease the application to a total of 400 to 600 grams per square meter.

    **If you have poorly drained soil, space the application out over a much longer period to avoid drowning your plants.

    This post was edited by Slimy_Okra on Mon, May 5, 14 at 13:33

  • toxcrusadr
    9 years ago

    Ah, great idea, iron sulfate.

  • Hill_Gardener
    Original Author
    9 years ago

    Thank you all for your input. I have run a pH test using a cheap garden-centre bought kit. The soil appears to be at 8, so it would seem that, as Slimy_Okra predicted, the slaked lime has returned to calcium carbonate. The one issue I have with the the kit is it doesn't register above pH8, is this is a universal feature?

    Slimy_Okra: many thanks for your advice, it is much appreciated. I thought I had seen the back of Ferrous Sulphate last month after spreading 50 kg of the stuff on mossy lawns a month ago. I will go and get some more and do as you say.

  • toxcrusadr
    9 years ago

    So your pH could be 8, or 8.5, or 9...or anything above 8. I don't know if this limit is common with test kits since I haven't used them, but it makes sense because most soils don't go above that, at least not naturally. :-]

    You'll have to decide whether this is enough of an emergency for your plants that you want to go find out how high it actually is. If you can add acid and see it drop below 8 it's a moot point, but how much acid and how long that will take is the big question.

    Good luck and let us know how it goes.

  • Slimy_Okra
    9 years ago

    If you don't want to do a professional soil test, can you get your hands on pH paper? It's more accurate than the soil kits. Mix the pulverized soil sample thoroughly with 2x the volume of water in a tall, narrow container. Allow it to settle for 30-45 min, then use a small container to scoop out some of the liquid from the top. If you can pass this through a coffee filter, do so. Dip the pH paper in it for a full 20 minutes and then read it.

  • Hill_Gardener
    Original Author
    9 years ago

    Just to confirm,

    application rate: 150g per square meter everyday for five days.

    I've just applied that rate in 10l of water (so half the amount, 750g, for a total area of 10.5m2). It seemed an awful lot of iron.

    Have I got it wrong?

    Should I spray off the residue on plants with water?

  • toxcrusadr
    9 years ago

    Sounds right according to slimy okra's post. Definitely rinse off plant leaves with a fine spray of water, the acid is probably not good for leaves.

    You'll want to check pH while this process is going on, i.e. after it's sat for a day and before adding more, to see where you're at.

  • Slimy_Okra
    9 years ago

    Yes, monitor the pH as you go.

    It is a lot of iron but it quickly oxidizes and then reacts with lime to get locked up as completely insoluble ferric carbonate. As long as the soil pH stays above 6.0, it will stay locked up and inert.

  • shuffles_gw
    9 years ago

    I am no expert, but it seems that all that calcium might overbalance the magnesium. You might need to add something like Epsom salts. Hopefully someone with more knowledge will chime in on this. I would love to know the answer.

  • Hill_Gardener
    Original Author
    9 years ago

    Hi

    I'm still having trouble with the figures; for a single application do I spray 150 mg in 20l water on EVERY SQ METRE for five days?

    Thanks

  • toxcrusadr
    9 years ago

    Yes, but it's GRAMS not milligrams. That's what I got out of this post:

    "That means you have to add about 700 to 900 grams of iron sulfate heptahydrate* per square meter. Apply 150 grams daily for five days, dissolving it in at least 20 L of water per application per square meter."

    This thread is three weeks old, how much have you applied up to this point and how are your plants?

  • Hill_Gardener
    Original Author
    9 years ago

    Thanks for the support. Numbers are not my strong point. I've done 1 day's worth of application at the rates above - grams not mg - a typo.

  • toxcrusadr
    9 years ago

    Keep pouring it on! How are the plants?

  • Hill_Gardener
    Original Author
    9 years ago

    Just a quick update - I finished adding the sulphate of iron a while ago. The plants were in a bit of a state, blackened in parts to a crisp despite washing off the excess solution with water. The soil is heavy inorganic (I think) black clay and full of stones. I used the recent spell of dry weather to dig over the soil and add well-rotted muck at 50l/sq m. The plants - phloxes and astrantias planted last year and smaller 9cm pots of veronicastrum, bugle and persicaria were re-potted and have now been replanted.

    I hope this works.

    Seconding shuffles' post, should I add epsom salts? Will a standard (cheap) soil analysis kit detect low calcium?

  • toxcrusadr
    9 years ago

    You really should get a good lab test for both Ca and Mg to know. I don't know for sure but I doubt there is a test kit that will give you accurate results for both of those (or even whether there are any home test kits that do Mg). It's not just whether Ca is low, the ratio of Ca to Mg is also important. Meanwhile I wouldn't add amendments based on guesswork. There's another thread here right now where someone has been adding Epsom salts to planting holes for years, and Mg levels are higher than Ca in their soil, a situation I have not actually observed before!

  • Hill_Gardener
    Original Author
    9 years ago

    Help, my plants are dying, is this iron deficiency?

  • toxcrusadr
    9 years ago

    It could be, but you would want to treat the cause. Do you know your pH now after all that ferrous sulfate addition?

    They certainly do not look happy.

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