Dolomite lime is used everywhere.  They’ve done a tremendous marketing job convincing us that we need to put this stuff on our lawns and gardens every year.

A search through both conventional and organic gardening websites and books reveals that most garden experts happily pass on this information.

Occasionally, using dolomite lime is warranted, but the truth is, it often makes things worse, sometimes just a little, and sometimes a lot. Let’s look at why…

What Is Dolomite Lime?

Dolomitic lime is a rock. It can be quite pretty. It is calcium magnesium carbonate, CaMg(CO3)2. It has about 50% calcium carbonate and 40% magnesium carbonate, giving approximately 22% calcium and at least 11% magnesium.

When you buy it for your garden, it has been ground into granules that can be course or very fine, or it could be turned into a prill.

Now, dolomite lime fertilizer is certainly allowed in organic gardening. It is not inherently bad, but how it is used in the garden is usually mildly to severely detrimental.

Why Are We Told To Use Dolomite Lime?

I have touched on this before when I talked about pH. The idea is that minerals in your soil are continuously being leached by rain and consequently your soil is always moving towards more acidic.

Dolomite limestone is used to counteract this, to “sweeten” the soil. It can do that, but that doesn’t mean it’s good.

Why Are Minerals Leaching From Your Soil?

Minerals may or may not be leaching from your soil. If they are, it could be partially because of rain, but there are other reasons, too.

If your soil is low in organic matter, which is generally the case, it probably can’t hold onto minerals very well, especially if it is low in clay and high in sand and silt. If you have lots of clay, you probably don’t have much to worry about.

Chemical fertilizers cause acidity, so if you use them, that is part of the problem, too. Dolomite lime fertilizer is not the answer. Organic gardening is. Let’s look at why dolomite is probably not what you want.

Here’s The Important Part

The main point I want to make is that even if minerals are leaching from your soil, it doesn’t make sense to blindly go back adding just two of them (the calcium and magnesium in dolomite lime) without knowing you need them. You might already have enough or too much of one or both of them. We need to think a little more than that when organic gardening.

Your soil needs a calcium to magnesium of somewhere between 7:1 (sandier soils) and 10:1 (clayier soils). Outside of this range, your soil will often have water problems, your plants will often have health problems and insect and disease problems, and you will have weed problems.

One of your most important goals in the garden is to add specific mineral fertilizers to move the calcium to magnesium ratio towards this range. As a side note, I understand it may seem strange to some that we should have to do this, but our soils are way out of balance and we’re trying to grow things that wouldn’t naturally grow there, so we have to do this.

The problem with dolomite lime? It has a calcium to magnesium ratio of 2:1. That’s way too much magnesium for most soils. Magnesium is certainly an essential mineral. Too much of it, however, causes many problems, compaction being one of the most common, but also pest and weed problems.

So if you add this to your lawn every year, chances are you’re just causing more compaction and weed problems.


Bottom Line:  It’s hard to find for a reason.  Don’t use it.  If your pH is low, use pH UP.  If you need a Calcium/Maganese supplement….  use Cal-Mag or CaMg+.


Courtesy of: Smiling Gardener