Organic soil management is a science and an art.

Conventional soil science teaches that soil is a relatively inert medium, an anchor for plants made of sand, silt and clay and a handful of nutrients for plant growth. If soil has enough nutrients, gardener’s will be okay.

Of course, organic soil management is so much more than that. Yet traditionally, not much has been mentioned about organic matter and next to nothing on the soil food web.

In many soil textbooks, you would likely find multiple chapters on fertilizing with nitrogen, phosphorus and potassium (NPK) and next to nothing on organic matter and botany. Fertilization is seen as the number one soil management strategy in many textbooks.

But this is organic gardening, and I’d like to present the story of healthy soil as a vibrant, living community. Of course, even organic soil is composed of sand, silt, clay and minerals, so I’ll talk about that, too.

And I’ll talk about soil testing, which isn’t particularly complicated but there are some things you need to know to do it right. I’ll get into organic soil amendments

Here are my articles on organic soil management…

Curling Leaves On My Tomato Plant
Curling leaves.

If you’re going to buy manure or use manure in your organic garden, you’ll want to read this email I received from Janet, one of my readers. It’s a good story with a very important warning:

“I have a sad composting/soil tale to share that I’d like to share with as many gardeners in the area as possible so please pass this along.

As many of you know, I’ve been an organic gardener for many years, making my own compost, using natural ingredients. I might buy manure or find it free. Last week I diagnosed a problem with my soil, specifically with some of my tomato plants due to a batch of “killer manure.”

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There are a few important things you need to know about where to buy compost.

When possible, I encourage people to make their own compost, but I understand, sometimes it’s just easier to buy your compost.

So in this article, I’ll discuss the main types of compost and then I’ll share a whole list of tips for how to buy compost.

So let’s get into it…

"Regular" compost
“Regular” compost
Worm compost
Worm compost

Main Types of Compost

  • “Regular” compost. Sometimes called thermo-compost or aerobic compost but mostly just called “compost,” it’s made with a diversity of ingredients mixed together in piles or long windrows. Those ingredients are broken down primarily by microorganisms.
  • Worm compost (vermicompost). Similar to the above, but it’s worms that break down the ingredients (along with the bacteria inside their digestive systems). Neither regular or worm compost is inherently better than the other. They each can have their own slight advantages but much more important is the quality and diversity of materials being used and the quality of the whole process. In theory, it could be optimal to use a combination of both and I say go for it if you have the chance, but you’ll get most of the way there from just one good compost.
  • Composted manure. As for quality, it depends entirely on what’s in it. If it were just animal poo that was left to compost on its own, it probably wouldn’t be particularly nutritious or biologically diverse, but if it’s mixed with straw and other materials, it becomes more and more like regular compost.
  • Mushroom compost. It’s generally not great. Yes, it is organic matter, but 1) It’s probably been sterilized, killing the microorganisms, 2) The mushrooms that were grown on it took out a lot of the nutrients, and 3) If they were non-organic mushrooms, it may contain a fair amount of pesticide residue.

Basic Compost Buying Tips

Bagged compost
Bagged compost
Bulk compost
Bulk compost
  • You can buy compost in bags, and that’s fine for a small garden or for container gardening, but I almost always go for bulk compost because it’s much less expensive and I usually want to bring in at least a cubic yard (3ft x 3ft x 3ft), which is 765 liters of compost – that would be a lot of bags!
  • When buying compost, it should smell good, not like garbage. If it smells like ammonia, it’s not done.
  • I shouldn’t have to say it, but it should not contain garbage. I once received a load of 15 yards of compost that was full of pieces of plastic, produced by a recycling company. I got my money back.
  • When searching for where to buy compost, it should look and feel like dark, moist, fluffy soil. You may see some wood fragments in there but if you can still make out a lot of the raw materials, it’s not done. That stuff may work well as a mulch but it’s probably not a great compost.
  • For the most part, we want our purchased compost to be 100% compost – not mixed with soil. There are cases when you may want to bring in compost + soil, like if you’re building a raised bed or changing the soil grade, but for the most part, you probably want only compost.

Advanced Compost Buying Tips

When I say “advanced,” what I really mean is that these steps take more effort and I understand most people won’t want to devote the time, but if you’re growing a lot of food, for example, it’s well worth it.

  • Find out what they’re using for raw materials:
    • You want some combination of leaves, grass clippings, plant trimmings, food scraps and manure.
    • Ideally, you’d want these raw materials to be organic or at least pesticide-free but that can be impossible to find (one reason why making your own compost is even better). So yes, unless you manage to buy compost from an organic farmer, you’ll probably have to live with a bit of pesticide residue from the grass clippings, leaves and plant trimmings. A lot of that should be broken down by a good compost pile and the small amount that is left over should eventually be broken down in the soil.
    • Preferably, you don’t want peat moss. It just doesn’t add much value and we need to leave peat blogs alone.
    • You don’t want toxic waste, industrial sewage sludge (aka biosolids) or “inert” ingredients.
    • You also don’t want tree bark to be the main ingredient because it’s not particularly nutritious and it contains compounds that can inhibit plant growth.
  • Ask for test results. A chemical analysis will give you element levels (e.g. nitrogen, calcium) and a biological analysis will give you microbial levels (e.g. bacteria, fungi). Most compost producers won’t have this info, and even if they do, the truth is that the results probably vary quite dramatically with each batch of compost they make, but here’s the point: if you can find someone who will give this to you, it shows that they really care about making good compost and they care about showing this to you.
  • Test it out yourself. If you have a few compost options, bring home a little of each and do some tests in containers or trays. To be most accurate, you’ll want to mix each compost option with the growing medium you’ll actually be using, like your garden soil. I won’t go into detail on this here but hopefully you understand what I’m proposing.

Where To Buy Compost

I can’t keep tabs on the thousands of independent compost producers around the U.S. and Canada, not to mention the rest of the world, so I can’t create a list of local composts.

But here are some basic tips:

  • Garden centers. They often have compost in bulk and almost always have it in bags. For the bulk, they may allow you to bag your own for a good price, or they’ll deliver by the cubic yard.
  • Topsoil/mulch suppliers. You may also find businesses in your area that just focus on selling topsoil, mulch, and compost in bulk.
  • Big box stores (e.g. Home Depot, Lowes). They don’t usually have bulk compost but they will have bags. The prices are good but the compost generally isn’t.
  • Craigslist (or similar, e.g. Kijiji in Canada). You may find compost here. I’ve also found composted horse manure (side note: I’ve also found straw bales that I used as mulch). If you don’t see any ads, you could post your own ad requesting horse manure. You may find horse manure that’s already been composted, but it’s also likely you’ll need to compost it yourself for a few months. Horse manure often comes already mixed with straw, so it’s basically ready to be composted as is.
  • Amazon. You can buy bags of compost on Amazon. Again, bagged compost is expensive, but if you have a tiny garden or are growing in containers, it could be an option:
    • For “regular” compost, there’s Charlie’s Compost at $18 for 10lbs. The ingredients are “chicken manure, corn stalks, straw, forest products, hay, clay, and beneficial microbe inoculants” and it’s “Certified Organic by the state of Kentucky.” I actually emailed them and they promptly sent me their Soil FoodWeb test results, which were impressive.
    • For worm compost, I found Wiggle Worm Worm Compost ($31 for 30lbs) and VermisTerra Earthworm Castings ($20 for 10lbs). Both are certified organic and look good.
  • Peaceful Valley.
    • They have certified organic bagged compost for a relatively good price at $7 for 40 lbs (1 cubic foot) and they also sell it in bulk at the ridiculously high price of $259 for 2 cubic yards. They have a note that’s disconcerting, “this green waste compost may still contain small amounts of non-organic foreign objects (glass, metal, plastic, wood, etc),” but the label just says “composted yard trimmings” so I don’t think they’re actually composting construction waste (some companies do this – I’ve seen it).

Compost Pricing

First of all, pricing varies dramatically.

For bags of compost, you could pay anywhere between $0.30 and $20+ per 10lbs (0.2 cubic feet).

For bulk compost, you could pay $10-150+ per cubic yard (27 cubic feet).

But even with these wide ranges, if you do the math, buying compost by the cubic yard is waaaaay less expensive than buying it in bags.

For example, let’s say the average is $10 for 30 lbs of bagged compost (0.6 cubic feet) and $40 for 1 cubic yard of bulk compost (27 cubic feet). That’s about 45 times as much compost for just 4 times the price, i.e. 10X less expensive (you do still need to get the bulk compost to your home, but it’s still a big difference).

So as I’ve said, I go for bulk. And I don’t tend to go for the most expensive stuff because I’ve seen too many examples of it being not only average but inferior.

For example, when I lived out west, there was a product made with a lot of bark that sold for $75/yard and caused problems on a couple of my friends’ gardens.

I’ve usually been able to find something decent for $30-$40/yard in the places where I’ve lived.

Here’s an article where I show you how to use compost in your garden.

Soil Testing Labs Need A Good Sample
Be sure to combine soil from a few places in your garden before sending.

I’ve written a lot here about the importance of using soil testing labs in order to determine which organic fertilizers to use.

Otherwise, you’re stabbing in the dark. But I haven’t actually told you which testing lab I use.

While it may be tempting to drive a sample over to your local soil lab, it’s probably not the best option. Right now, most soil testing labs aren’t doing a great job.

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Rock Mulching With Leaves Is The Best Mulch

I’ve written already about the best mulch types to use in your organic garden, but here I’ve put together a video that shows a rather amazing rock mulching technique I didn’t talk about before.

If you have certain bigger plants that are special to you, like a new fruit tree for example, you can use rock mulching with leaves to make the best mulch for improving the soil extremely quickly, resulting in amazing plant growth.

Place a few inches of leaves – which I’ve already shown are the best mulch type – around the root zone of the new tree. Cover those leaves with round stones or flagstones that are small enough so that you can handle them, but big enough to cover some of the leaves.

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Sheet Mulching In My Organic Garden
In permaculture, sheet mulching is often done near the house to prepare a kitchen garden.

Sheet mulching is one of the best methods of building an organic garden, and today I’m going to show you how to mulch correctly to make a great sheet mulch. You may have also heard it called no till gardening or lasagna gardening, both of which mean the same thing.

There are many ways to make a yummy lasagna and there are many ways to make a sheet mulch, but no matter how you do it, you can think of sheet mulching as kind of like composting right in your organic garden. It’s mostly done to create new garden beds, and occasionally in existing vegetable beds during the fallow season.

Sheet mulching is an amazing way to smother weeds and build fertility and soil structure at the same time by layering various materials anywhere from just a few inches to 18 inches high.

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Dolomite Lime
Broadcasting dolomite lime on the lawn

Dolomite lime is a common fertilizer.

Many garden writers encourage you to spread it over your garden and lawn, perhaps even annually.

Sometimes using dolomite garden 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…

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pH Test For Soil
pH Test For Soil

I recently showed how doing a pH test for soil might actually be detrimental.

You should probably read that article before this one. Today, I will discuss if it is ever useful.

The bottom line is that keeping track of pH is not necessary in most cases.

There are times when a regular pH test for soil on intensively managed farms and gardens can give you a hint as to whether your soil is becoming more acid or alkaline because of something you’re doing, so you can know if it’s working.

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Soil pH Kits
pH paper

Soil pH Kits give one of the most misunderstood and misused measurements in the conventional and organic gardening worlds: pH.

It’s a fascinating topic and I’m excited to get into it here.

If you can get your head around the information in this article (it may be no problem for you, but it took me a while to get it), you will know more about pH than most gardeners, including most horticultural professionals, teachers and authors.

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