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Liming Acidic Soil – Adding Lime

Your soil is acidic and you would like to change the pH so that it is less acidic. The universal advice is to add lime to the soil ie liming your soil. Lime is alkaline and it will neutralize the acidity of the soil and make it more neutral. Adding lime certainly works – but there is a catch!

Liming acidic soil

Anemone Pamina at Aspen Grove Gardens

What is Lime?

Strictly speaking lime is calcium oxide or calcium hydroxide, but the term is also used to describe a wide range of calcium-containing compounds. Agricultural lime is usually calcium carbonate, or limestone. All of these soil conditioners will neutralize acids and make them less acidic.

 Liming – What Happens in the Soil?

Soil is able to ‘buffer’ itself. What this means is that you can add a bit of lime to acidic soil, and the pH of the soil does not change. This ability of the soil to neutralize the lime is called ‘buffering’. If you keep adding more and more lime, you will reach a point where the soil just can’t buffer any more, and the pH will start to go up. How much does your soil buffer? That is an important question when adding lime because you need to add enough lime to overcome the buffering effect and then add more to change the pH.

The buffering effect of soil can be measured and it is called the “Buffer pH”. Without knowing the Buffer pH, you simply do not know how much lime to add to your soil.

 How do You Measure Buffer pH?

A commercial soil testing lab can measure and report the “Buffer pH”. Using this value it can then recommend the amount of lime you need to add to the soil.

In a previous post I discussed the accuracy of soil testers in  Soil pH Testers – Are They Accurate?, but an even bigger problem with these testers is that they don’t measure Buffer pH.

Since garden soil kits don’t measure the Buffer pH, they aren’t much use for adjusting the pH of acidic soils.

Liming Lawns

A lot of gardening information recommends that you should add lime to your lawn on a regular basis. As you can see from the above discussion you can’t know how much to add without a soil test. Don’t add lime to your lawn unless a soil test tells you that it is required.

If you are trying to get rid of moss in your lawn because of the acidity have a look at this post; Why Does Moss Grow in My Lawn?

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Robert Pavlis
Editor of GardenMyths.com
I live in southern Ontario, Canada, zone 5 and have been gardening a long time. Besides writing and speaking about gardening, I own and operate a 6 acre private garden called Aspen Grove Gardens which now has over 3,000 perennials, grasses, shrubs and trees. Yes--I am a plantaholic!

I hope you find Garden Myths an educational site that helps you understand your garden better.

8 Responses to 'Liming Acidic Soil – Adding Lime'

  1. Allison says:

    I’ve read evenly taken down a bunch of cedars that have been growing for 24 years. They had to come down for safety reasons. But my soil is acidic and I want to make it more neutral. Is there anything else besides lime that would help with the process? I don’t want the soil to become toxic with an abundance of calcium.

    • Get a soil test and they will tell you what to add. Why not live with your pH? Changing pH is a never ending battle and rarely worth the effort for home owners. Grow things that love acidic soil.

  2. Gypsum improves the soil in my area in California which is a fine silt that behaves like clay. Gypsum makes the soil percolate water, improves tilth, and adds calcium but does not change the pH. My understanding is that calcium takes the place of sodium, changing the soil’s structural properties, especially when it is heavily watered to permeate the soil and remove sodium. I only know that it works.

  3. Luke says:

    Will lime make the soil more fertile

    • Robert Pavlis says:

      Lime is a form of calcium oxide. The only part of this that would be used by plants is the calcium part. If your soil is deficient of calcium, then lime would be one way to add this element. However, most soil has lots of calcium in which case adding more calcium will either have no effect, or it might make the soil toxic by adding too much.

      Unless you have done a soil test and it shows a lack of calcium, or you have very sandy soil which has few nutriments of any kind, assume you don’t need more calcium.

      • Hi Rob, i just left a not-flattering comment on another article of yours and now I’m following up with this … You might think I’m trolling you. That’s not the case, I’m researching soil amendments for my poor lateritic acidic soil, hence exploring your site.

        Your answer to above comment from Luke, while being technically correct, is so utterly misleading !

        Low ph makes a lot of soil nutrients unavailable … Notably P and K. Also N. So if your big 3 macro nutrients are less available in soil due to low ph and adding lime is going to raise the ph, then definitely liming makes your soil fertile !

        • Raising pH does not make soil more fertile. It can make the existing nutrients more available to plants – but changing pH does not change the amount of nutrients in the soil.

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