correcting acid soils

Discussion in 'Planting, growing, nurturing Plants' started by dunc, Jun 16, 2009.

  1. dunc

    dunc Junior Member

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    Hi....

    Ive been wondering when the best time is to correct acid soil with lime and / or dolomite, in a crop rotation system.

    I like to incorparate composted cow manure and worm castings into the crop rotation bed in between crops. If I add lime or dolomite at this time will there be nitrous oxide or some other undesirable reaction in the soil.

    Should lime and dolomite be avoided altogether, and just buffer the soil pH with the organic matter and composts and worm castings?

    Mark
     
  2. gardenlen

    gardenlen Group for banned users

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    Re: correcting acid soils

    g'day dunc,

    dolomite is lime with a plus as far as i know never heard anyone say to use both lime and it at the same time, so it will work alone.

    did you do a ph to determine the acidity of your medium?

    test kits are not that accurate so i gave up even tough we had bought the supposedly best kit around at the time. for me if the plants are growing and are healthy in appearance then the ph must be ok. but if you need to dolomite can be added anytime as i understand it you could mix it in water ans water it around the root zone of the plants of blanket the whole bed, or pull the mulch back and broadcast the dust over the surface of the bed, at the prescribed rate per meter as suggested on the pack.

    len
     
  3. dunc

    dunc Junior Member

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    Re: correcting acid soils

    I have done many pH tests on the soil and it ranges from 4.5 to 6. The orginal soil was 4.5, a sandy coastal heathland soil. I havent imported commercial garden mixes. I am gradually building up the organic matter so I think most of the garden is now around 6, three years of organic matter, dolomite, composts and manures. It looks good. Id like to get a soil test done by the soil food web institute to see jow the soil life is. I regulary give advice to new veggie gardeners in the area so I want to make sure im doing it right.
     
  4. gardenlen

    gardenlen Group for banned users

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    Re: correcting acid soils

    g'day dunc,

    isn't around 6 close to neutral?

    if the plants are growing well and look healthy then i'd suggest you are doing the right thing. by using natural products or as natural as can be ie.,. hay's or sugar cane mulch instead of adding in man made fertilisers i reckon your medium will be in balance organic matter wise and ph wise, it has never failed us so far that after 10 years or so using these methods. all that goes on our gardens is s/c mulch or hay mulches, kitchen scraps and used water with urine added too easy. all our composting/vermicomposting happens in the gardens, spent plants get composted where they once stood, prunnings around the trees they came from as we mostly only have food trees.

    len

    https://www.lensgarden.com.au/
     
  5. Michaelangelica

    Michaelangelica Junior Member

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    Re: correcting acid soils

    You would be amazed at how much organic matter that sort of soil can handle. literally truckloads. there may also be some residual salt in the soil too which micro-organisms will help break down.
    Dolomite is easier to use than lime, more natural and contains magnesium.
    If you are worried about NO2 dig 2-300 grams of fine charcoal into every sq meter of soil ( do a pH test on the char first-- it can vary) This will also encourage soil micro-organisms. (See the "biochar" and "terra preta" links here).
    So too will sugar or you can buy 3K of bacteria for about $22 from Olsen's GreenBio [/b]Imported by Galaxy Ford international stocked by some Bunnings stores.

    Most vegies like a pH of about 6.5. Seven is neutral. While the difference between 6 and 6.5 does not sound large remember it is a logarithmic scale --as used for earthquakes-- so the difference is quite large

    I agree pH detectors are not great. Most of us do with the CSIRO test kit ( about $20)
     
  6. gbell

    gbell Junior Member

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    Re: correcting acid soils

    Boy there just seems to be about 10,000 of these types of 'magic' products. Anybody know a good way to separate the fairy dust from effective products? Maybe a good scientific testing body that works faster (and is more interested in alternatives) than CSIRO?
     
  7. SueinWA

    SueinWA Junior Member

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    Re: correcting acid soils

    Don't use lime to raise the pH -- pH is only the pointer that something is wrong.

    You need to get your calcium and magnesium levels right first, and that has to be determined by testing -- you can't see it visually in the crops until it's really wrong (too high or too low). Once you get your soil balanced, the pH will fall into place naturally. While many people speak of neutral soil (7) being best, most crops really prefer about 6.5, as Michaelangelica pointed out. There is a difference between what a certain crop prefers and what it can tolerate.

    If you have heavy clay soil, you would want about a 70% calcium level and 10% magnesium. If your soil is sandy, 60% calcium and 20% magnesium would be better (notice that they both add up to 80%). Some soils have enough calcium but not enough magnesium, or vice versa, and that fact will determine which sort of calcium you should be using (dolomite, gypsum). Don't use one when you should be using the other, or you'll just be paying good money to create more problems.

    And remember that even the finest grind of lime will take a minimum of three years to break down in the soil, roughly one-third each year. Coarse lime can take up to ten years. So, if you are sending in soil samples, BE SURE to tell them when you limed that soil, so the lab can allow for it when they give you advice on what to do. If you don't, you can end up with overlimed soil. What is there, and what is available are often two different things.

    Usually, calcium is added in the fall (to start breaking down into the soil during the winter), and nitrogen is added in the spring, as it can be leached out by heavy rainfall if added too soon. I seem to remember faintly some advice that nitrogen and calcium shouldn't be incorporated into the soil at the same time.

    Manure doesn't usually add any calcium to the soil unless it comes from laying hens who were fed extra calcium for egg production, and the extra is excreted in the manure.

    Get your soil test done and see what your calcium levels are BEFORE you lime the soil, so you'll know where you are to start, and where you want to go. It will help to prevent expensive mistakes.

    Note: Always get your primary nutrients (nitrogen, phosphorus, potassium) and secondary nutrients (calcium, magnesium, sulfur, sodium) lined up correctly before you start adding your micro-nutrients, or you will be wasting your money. Plants cannot do well with just the primary nutrients.
     
  8. gbell

    gbell Junior Member

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    Re: correcting acid soils

    Just to put a finer point on it...

    I often see dolomite lime recommended over ag lime "because it has magnesium in it". But this isn't a case of "more is better". The ratio of calcium and magnesium is what matters (Ca:Mg) and it should be in the range of 2:1 to 7:1. Dolomite has a Ca:Mg of 2:1, so applying it will lower the ratio in your soil. That may be what you want, but your soil test should be your guide. (I realise that if 2:1 is in the acceptable range then that should mean applying 2:1 is always OK. I wonder this too. I would guess that aiming for the middle of the preferred range is better than being right on the boundary).

    Also, I see many sources contradict what the author above said. While organic matter and bringing the soil back to life are essential and will correct minor pH problems, often people recommend correcting the pH problem first to jump start the soil and make it possible to grow plants. pH too high/too low makes nutrients unavailable/overavailable.

    Source: Soil Sense, Soil Management for NSW North Coast Farmers, Rebecca Lines-Kelly.
     
  9. SueinWA

    SueinWA Junior Member

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    Re: correcting acid soils

    "... often people recommend correcting the pH problem first to jump start the soil and make it possible to grow plants. pH too high/too low makes nutrients unavailable/overavailable."

    High or low pH is just the INDICATOR, not the source of the problem. That thermometer on your porch is INDICATING the existing temperature, it isn't controlling the heat from the sun.

    When you add lime, you are adding needed calcium, and a rise in the pH is what follows the raising of the calcium to within acceptable levels. But because the lime is slow to break down into usable forms of calcium for the plants, you're not going to have any kind of instant effect. And until it is broken down, your soil will still be out of balance. And only a professional soil test will tell you that.

    To have balanced soil, you need to be paying attention to everything. If the soil is out of balance in any way, the distortion will cause problems. If your magnesium levels are fine, you shouldn't be adding more magnesium by way of dolomite lime, or it's going to throw something else out of balance, like binding up potassium so it isn't available to the plants.

    From agronomist Neal Kinsey: "Proper soil levels of calcium (60-70%) improves soil texture, makes phosphorus and micronutrients more available, improves the environment for microorganisms, helps plants form better root systems, stems and leaves for efficient use of sunlight, water, CO2, nitrogen and mineral nutrients... Every other nutrient has to ride on the back of calcium to get into the plant. Calcium puts the starch into the leaf, activates several enzyme systems, increases yield by reducing soil acidity, and improves microbial activity."
     
  10. Ichsani

    Ichsani Junior Member

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    Re: correcting acid soils

    Hi Mark,

    Dolomite would be my choice over lime for the home gardener.

    Back of the hand calc for a sandy soil using dolomite (if neutralising value (NV) is ~67%)

    *for every 100g/m^2 of dolomite used it will lift a mineral soil up 0.3 pH points (to 10 cm deep)* ... so if you want 0.3 pH points (up) to 30 cm deep its ~300g/m^2; or if you want 1 pH point (up) to 10cm deep then its also ~300g/m^2 etc etc etc ... :)

    As to when to apply.... as you're trying effect the mineral phase of your soil (in terms of pH) then don't put it on at the same time as adding organic material (as org matter has a much higher buffering capacity than even good clays - it'll 'suck up' your dolomite rather than it making it onto the mineral phase where you want it .... applying dolomite with org matter is not an issue if you are adding dolomite for nutrient purposes as opposed to adjusting pH (I do both in my own garden and recommend both depending on the purpose)).

    So to be practical (as I can be!) - add required dolomite in 'lots' of say 100 g/m^2 at a time and repeat the following year/s till the pH is where you want it - mix/rake it into the soil to desired depth as opposed to broadcasting on top and watering... application for pH change would be best done when digging in a green manure (green manure will behave differently in soil to already composted org matter) or a few months before compost application (I don't know your crop cycle but I hope you get what I'm saying).

    For sandy acidic heath soils in Oz i strongly recommend an input of dolomite (or lime)... it'll make you gardening that much easier.

    There won't be any nitrous oxide (N20) produced if you add dolomite with org matter - nitrous production is more related to the abundance, species and location of N present in the soil and whether it is aerobic or anaerobic (ie waterlogged soils with high N levels will produce nitrous oxide (gas), whereas well aerated/structured/drained soils are more prone to leaching of NOx). As I understand, in organic growing systems there's less of an issue with nitrous production, usually the buggies take the NOx all the way back to N2 gas (its an energetic opportunity - N20 is a waste (the step from N2O to N2 can be used by buggies in the soil), N2 can't be used anymore unless you're a n-fixing bacteria.... blah blah :)). Leaching of N would be a bigger risk but still pretty small for a home gardener (especially a permie!).

    Hope something there makes sense.

    Happy gardening :)

    Cheers
    Ich
     
  11. gbell

    gbell Junior Member

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    Re: correcting acid soils

    OK, Sue, explain it to me like I'm three! Low pH means few H+ ions, right? So how do nutrient deficiencies relate to too few H+ ions? (Since text is such a terrible conveyor of tone, my "tone" is meant to be that of an amateur enquiring earnestly!)

    And can't the "indicator" of high pH be an indication of not enough lime applied? Why must the "problem" be something other than not enough lime? You're indicating that there are "problems" causing the pH imbalance, but I guess I'm confused at what those problems are and are not.

    Cheers,
    Greg
     
  12. dunc

    dunc Junior Member

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    Re: correcting acid soils

    Well thanks for the run down on soil science. There are so many variables, and its very interesting.

    My gut feeling is that the dolomite if required would be best added when digging in your green manure crop.

    Coincidentaly I am planting a green manure of Mustard (Osaka Purple), to fumigate my soil after a crop of carrots. There is an area of the garden with the root knot nemetodes and it has had a devestating effect on the carrots in particular.

    The brocolli and all the other brassicas are doing really well in the OM improved sandy soils, and so does the asparagus.

    Raising the pH from 4.5 has been a slow but gratifying process. Thanks for all the info.

    Mark
     

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