Is Lime Sustainable Fertilizer?

Mining limestone is big business, but does it give us a sustainable fertilizer?

The world’s biggest limestone quarry is right near the top of the state of Michigan on Lake Huron.

It’s 7000 acres, roughly half the size of Manhattan.

I’m not sure how much of the material from this particular quarry goes toward agriculture, but lime is certainly one of the most important fertilizers in farming and gardening, especially in organics.

There are different kinds of lime, the best for gardening and farming usually being calcitic lime, which supplies mostly calcium and not too much magnesium.

The Importance Of Calcium

Calcium is critical in order for so many good things to happen in the soil and plants. Interestingly, it’s the most needed element by weight and volume for plants, and without sufficient calcium, nothing works.

While nitrogen and potassium get a lot of attention, more and more focus is being put on calcium, particularly in organic gardening. Calcium helps plant cells communicate with each other by physically moving between cell membranes.

Not only is it integral in the basic structure of plants, with a deficiency often showing up as thick, woody stems, it’s largely responsible for the availability of nutrients in plants and has a strong influence on microbial activity.

In the book Mainline Farming For Century 21, Dan Skow says “calcium is essential for its energy creation potential in the soil to release the other elements that cause a plant to grow.”

Why Considering Your Inputs Is Important

Lime is just an example. The point is, when we mine rocks like lime, they’re gone.

When you get into organic gardening, you start to think more about sustainable fertilizer choices and the sustainability of your actions outside the garden.

That huge quarry is going to run out of lime in 100 or so years. In the case of calcium, we still have plenty on the planet, but we’re actually getting close to reaching “peak phosphorus” (like peak oil but for phosphorus). That’s a huge issue.

Are you one of those people who think we should be gardening without external inputs? Without fertilizers and imported compost?

Because I am. And yet, I don’t know how to do it. I can do quite well with just compost and microbial inoculants such as compost tea and effective microorganisms – I can get maybe 80% of the way there. I can get a nice-looking garden.

And to be fully sustainable, we should be composting our own manure (“humanure”) and recycling as much on-site energy as we can (weeds, winds, water, etc.).

But if I want to get my food garden to a state of health where most pests go away and the food I grow gives me the nutrients I need to be healthy, I need balanced soil.

Unless I’ve been lucky enough to stumble upon balanced soil, it requires a bit of tweaking early on in my garden’s life.

Why I Often Need Some Organic Fertilizers

Of course, in a well-balanced ecosystem, external inputs aren’t necessary.

Nature does most of the work and there’s always some plant that will happily grow. But I’m growing many foods that simply wouldn’t grow in my soil naturally.

It’s not that I’m growing plants that are unsuitable for my climate. It’s just that in nature, plants only flourish in soil conditions that are right for them. Take weeds – they’re just the plants that are best adapted to your soil conditions.

So for the most part, I can’t just throw some veggie seeds onto my soil and expect them to be happy there.

Much of our soil has been tremendously altered by deforestation, tilling, chemical use, and on and on to the point where it could use a little help from us. We don’t want to wait hundreds of years for the soil to repair itself so we can grow optimally healthy food.

So this is why we may concede to ship some lime halfway across the country to get more calcium into our soil. Being environmentally conscious, we don’t want to ship this lime and we may not want to be mining limestone in the first place.

But we need nutritious food right now.

Sustainable Fertilizer – What Does This Mean For You?

If you’re wondering where to focus most of your attention for soil building, not to worry, it’s still on composting and mulching and plain old proper watering.

Even if you have a tiny backyard, you can get a small compost bin going, and all you need is a little dusting of it to provide you with most of the nutrients and microbes your garden needs.

It’s interesting, 95% of what your soil and plants need is carbon, oxygen and water. Organic matter helps with all of those.

But 5% of what they need is specific nutrients, and a few of those nutrients need to be in specific ratios in the soil.

That’s why you may need to bring in a few external inputs if you are serious about producing the healthiest plants, especially food. That’s when you take a soil test and add the deficient minerals. It may only be 20 pounds of organic fertilizer per 1000 square feet of garden.

Even in permaculture, which is a design approach that’s especially concerned with sustainability, it’s generally agreed that bringing in some inputs early on in the process to get things productive much more quickly is important.

So while I keep my inputs to a minimum, I do use them in the early years of a new garden, especially a vegetable garden.

What are your thoughts on this? Do you try to use sustainable fertilizer sources? Or do you try to get all of your nutrition from materials on your property?


  1. William on February 24, 2012 at 9:34 pm

    Hello Phil,I live on Vancouver Island, BC. Is oyster shells a good source of calcium? I noticed today I can buy it at the local feed store (already ground up/finely processed). I know we have quite a few oyster shell fish harvesters on the Island.Thanks William

    • Phil on February 25, 2012 at 7:58 pm

      Hi William, yes, go for it if the price is right. They are a good source if they’re finely ground up.

  2. Randy on February 25, 2012 at 4:41 pm

    You should really start monitoring the discussion on Steve Solomon’s Soil and Health Yahoo group

    • Phil on February 25, 2012 at 8:13 pm

      Thanks Randy, I’ll check it out. Certainly a fan of

  3. Morgan on February 25, 2012 at 11:28 pm

    What about eggshells? I throw them in the compost bin with the other kitchen scraps. And as far as decreasing external inputs, I think I will have to build towards that. This is the first season of gardening at my new place and the soil is in pretty bad shape. I have a lot of work to do. 🙂 I have started my compost bin, my worm compost, and have ordered some EM. Its a start, but I need to keep learning. Thanks for all your hard work!

    • Phil on February 27, 2012 at 10:34 pm

      Egg shells are great for either compost bin. Sounds like you’re on the right track.

  4. Joan121 on February 26, 2012 at 10:46 am

    I’ve read that wood ash is a good substitute for lime. We have a wood stove, and spread all the wood ash on the garden… This is a much more local source for many of us!

    • Phil on February 27, 2012 at 10:44 pm

      Hi Joan, it’s more for potassium. I would only use it if you know you have a potassium deficiency, because excess potassium causes some issues.

  5. Wansbek1968 on February 26, 2012 at 1:44 pm

    I have thrown in plenty of egg shells into the compost, my chickies give me more than just the manure!! What about comfrey?  Planting comfrey, a fair amt and using that as compost, in compost?  The roots go deep and bring up minerals, not sure about the calcium content though.  I have planting three blocking 14 comfrey plants. For the compost and the chickens.

    • Phil on February 27, 2012 at 10:45 pm

      Ya, comfrey is awesome if you can keep it under control, which can be tricky. I’m not sure about calcium content either, but calcium does tend to sink so perhaps it does bring it up.

  6. jonathan on February 26, 2012 at 6:57 pm

    i have a five gallon bucket full of eggs shells i’ve been collecting. i’m going to pulverize these into a powder for the garden. what are your thoughts on this method of adding calcium? & approximately how far do you suppose this will go per square foot?

    • Phil on February 27, 2012 at 10:47 pm

      Great idea Jonathan. I have no idea how far it will go. It doesn’t seem like much because when you pulverize that down it will become quite small, but I think it’s a good idea.

  7. Leonard Ang on February 27, 2012 at 2:48 pm

    What about fermenting burnt egg shells with vinegar?

    • Phil on February 27, 2012 at 10:48 pm

      Never heard that. Is it a traditional method, do you think?

      • Leonard Ang on February 29, 2012 at 9:52 pm

        Came across a YouTube video sometime ago. Apple cider Vinegar (or other fruit vinegars) is added to roasted egg shell to dissolve the calcium. The stock is allowed to ferment for a couple of days until all shells “disappear” (turns transparent). Strain the calcium rich solution and dilute with water. I think I was searching for Korean Natural Farming techniques when I came across this. Will try to see if I can find the link again.

      • Leonard Ang on February 29, 2012 at 11:00 pm

        Unfortunately I couldn’t find the same video that I have watched. Basically burning/roasting/baking the egg shells to kill any harmful organisms, I think. And by dissolving it, it’s ready for plants to absorb, something along those lines.

  8. Linda Fritz on February 26, 2017 at 9:17 am

    How do you feel about coffee grounds for calcium? Lots and lots of coffee grounds? Our church offers free coffee at the services and to save the coffee grounds from the landfill I’ve been picking up the grounds each week and spreading it over my fields. It’s about 30 gallons a week and I have about an acre that I plant on. I grow edamame and sun sugar cherry tomatoes. My soil ph has been sitting around 5.2 for the last 4 years even though I add about a ton of pelletized limestone each year. I came across your blog when I was trying to decide if limestone was a sustainable option even though the soil test recommended adding it.

    • Phil on February 26, 2017 at 11:06 am

      Unfortunately, coffee grounds aren’t a good source of calcium. They do have a little nitrogen and some other nutrients, but not much calcium. At the rate you’re applying it, it’s probably worthwhile as source of organic matter and some nutrients, but not to increase calcium or pH. Calcitic lime is the answer, and perhaps some organic liquid calcium to go with it, which you can find online.

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