When an online search for the word 'dirt' is performed, it is quite evident that "dirt bike" topics are the most common result, followed by use of the word "Dirt" as a very popular title of gardening newsletters, especially Master Gardener Associations. I find that interesting, since I am a Master Gardener, and as such are supposed to support land grant university AgriLife Extension Service programs - and the study of dirt is NOT one of those programs - only the study of soil... But, suppose gardeners should be grateful for whatever support for dirt we can get...

A few words about such an online search might be appropriate - since the number of entries will be over 73 million - and although I consider myself to be a patient researcher - it takes a lot of time to scan through all of those - and certainly view only a few in a hundred - knowing from experience that until getting past at least the first thousand entries, the research documents sought, will be 'buried' under 'tons' of public site entries - because search engines do not rate scientific, technical jargon highly. So far have not been able to find a quality technical search engine. Probably because jargon doesn't read like normal English...

It also seems to this author, that the word 'soil' is pretty much avoided (as a term), by many organic gardeners - who seem to know that the earth they work is not 'soil' any longer - so tend to call it 'dirt' instead - because (in my opinion) most have recognized that amending surface soil to the degree that it promotes thriving vegetable plants, changes it to a degree that it no longer resembles any natural soil they have ever seen.

As a proponent of organic (natural) gardening practices (in contrast to use of synthetic chemicals), I often wondered about how the soil science community would respond to an organics practitioner using the word 'dirt' instead of 'soil' to describe agricultural land that is managed to harvest "organic produce". Perhaps it's OK, since 'soil' distinguishes the soil science community from the 'common gardener' folk?
Would be interesting to hear from some large-scale (multiple-acres) organic commercial farmers 'out there' with regard to what they personally call whatever it is they grow plants in, with their tractor equipment.

The word "soil" is recognized as having scientific connotations to most commercial farmers, since the geological study of the earth's crust comprises discussion of technical mineral aspects of agricultural farmland - because that's what land grant universities call it. After about 6' down though - mostly only tree roots care - with maybe the exception of spelunkers...
Nowadays there's even a move by soil researchers to term the study of soil as "biogeological" which I certainly have no quarrel with.
About time, in my opinion...

Soil is also a 'generic' word used by 'laymen' to describe a full range of mediums that plants are grown in - including many that are definitely not even 'soil-like'.

Nowadays with wood chipping machines so popular, to utilize the abundance of cut-down trees (which enabled the 'mulch' industry), sometimes there's so much wood found in container mediums, along with inorganic ingredients, that it's actually hard to find enough non-cellulose organic matter to support microbe densities sufficient to sustain plants with natural organic fertilizer. Which is why so many 'greenhouse' establishments are "stuck" on using synthetic chemical fertilizers to feed containerized plants grown in soil-less mixtures.

Someday I'm going to locate a microbe population that can utilize cellulose/lignin in combination with another set of commercialized organic matter that will produce a balanced organic fertilizer from the artificial media that greenhouse growers put together. If I live that long...

Another issue that I think is funny is the use of the word 'loam' by the soil science folks, which means something totally different from what the 'average' person means when they say the word 'loam' - referring to the top several inches of organic matter that is represented by a sweet-smelling, crumbly forest floor.

According to the dictionary, what soil science calls loam is the material used to make BRICKS. Yup - the kind of stuff houses are made of - not the kind of stuff that grows forest trees: Noun.

  • 1. Soil consisting mainly of sand, clay, silt and organic matter.
  • 2. A mixture of moist clay and sand, together with straw, used pricipally in making bricks and foundry molds.

Now isn't that appropos? A really good example of how far off the descriptive word 'loam' means to most people with regard to growing plants in good soil, and what the word actually means in soil science.
Actually, in soil science, there is absolutely no mention of organic matter in the taxonomic description of loam - which is:
...Roughly equal parts of sand, silt and clay. Period.
Bricks that won't grow squat. No air or water required to be loam, taxonomically.

Point? That there is overlapping activity in the use of some terms in general use.
Does it matter? Well, in the scientific community it does, simply because technical terms are designed to convey specific meanings.
To this author? Nah. Not really, but just so none of the soil science folks have a 'beef' with my terminology, I'm gonna call what I make DIRT, not soil.

So what's the point? Soil science does not have much to do with DIRT. It's a pretty safe term for what I'm going to help you learn to make and use to grow plants.
But every now and then a soil scientist will 'slip up' and use the word "dirt".
Check out:
But then, being at a construction site, perhaps this example was disturbed sufficiently to be termed 'dirt'?. We can suppose...

Being a professional Master Composter Instructor, and Master Organic Gardening Instructor, with a website for the world to read, what this author has to say, is going to have a bit more impact than if my words were in hardcopy print form, and hopefully this discussion will become interactive - with you (the reader) asking some questions via my Contact link. Hope to hear from you.

Being an ardent microbiology researcher, with my own powerful light microscope, in my own laboratory in which I test compost and compost tea for microbe quantity and quality (diversity), I have some things to say to gardeners who care about amending soil to make it into fertile dirt, in which to grow their plants BETTER than they could in natural soil.
Because garden soil has been distrubed, and amendments have been added to it - what was, is no longer just soil. It is now dirt.

Do soil scientists really care about human-effort amended dirt? Yes, actually it seems some do, particularly in one special area of mutual interest. The soil (oops, I mean Dirt) that has been dubbed "terra praeta" that is located in the Amazon Basin of South America.
From what I read, this dirt was first discovered way back in 1841 - remains of an ancient civilization that dates back to 450-900 BC. Couple of thousand years ago.

However, this discovery remained 'in the shadows' until the 1950's, and became a focal point of great interest in the 1970's by soil scientists.
Because of the unusually high fertility of this dirt - that had been amended with human stuff - shards of pottery, plant refuse, manures, and a special kind of charcoal.
Some folks call that charcoal "bio-char" because it was created by LOW temperature fires. Apparently, on purpose, 'cause there's lots of it in terra praeta.

Suppostion reigns about why, but I personally think it had to do with making pottery - perhaps as a tribal commodity for trade? Nobody knows.
But charcoal has long been a well-known organic amendment to make dirt more fertile - but now the scientific community cares about it too. Charcoal is high-carbon material, but its principal value in dirt is the multitude of micropores that hold air, water and microbes.
No, we're not talking about wood ashes and just the smouldering remains of a bonfire from clearing land for agriculture. This was mud-covered fires.
Making charcoal is an art. So is bio-char, because nowadays CO2 emissions and other pollutants from burning organic material are big concerns.
Making lots of smoke is a no-no when making charcoal into bio-char. It's more of a 'cooking' process than a burning process.

Another area that soil scientists are concerned about is the devastating pollution and massive erosion of agricultural soils around the world, due to excessive disturbance of that soil by large machinery, and application of synthetic (chemical) fertilizers derived from fossil fuels.

The knowlegeable world's population is also in a bit of a 'tizzy' about that - because both food production - and the quality of food harvest nutrition - is declining, while the world's human population is increasing dramatically - without any signs of slowing down. Edible resources for humans are declining and will reach monumental proportions beyond 2030.

Well, my writings only address the world's problems of that scale of magnitude from a general perspective, and it seems to me (now in my later years), the main thing that I need to do is focus on passing along knowledge about the skill set I've learned over the years regarding composting and organic gardening and rainwater harvesting - and encourage as many individuals as possible, to do the same thing - and more of it.

In my opinion, composting and organic gardening at home is one way that every person can do their fair share, to make the world a better place.
Especially by not sending organic materials to a landfill - by composting them at home instead - and raising an abundance of fresh nutritious vegetables.

And encourage giving it away or barter for stuff - if you have extra - which is going to become even more important in the next several decades.
And teach somebody in a low-income bracket, how to compost and raise vegetables at their home too. Saves lots on grocery expense.

Part of what I teach is how to change organic material into aged organic matter (OM) for plant nutrition and health.
The fastest, most efficient method is to make compost and use the compost - which changes organic material into organic matter - with which to make diverse dirt 'recipes'.

But composting is not the only way. Putting organic material directly into the ground is often done too - that's just not the fastest, best way.
Done mainly by people who don't know how to compost - or for some reason don't think that they have space to compost. But composting can be done in 5-gallon buckets, garbage bags, or 30 or 55-gallon barrels too. Lots of different methods.

Dirt can be used to grow plants by itself, OR you can add dirt to the ground you have, which may or may not still be soil.
To make the dirt better, means more productive plants, and high-quality dirt helps protect plants from natural pests and diseases.
Which means people should learn how to amend whatever they plant in, with whatever organic feedstocks they have on hand.
Or can easily and inexpensively get, and barter/trade for.
Time and effort are two things that everybody has - if you're still breathing and still able to put your clothes on by yourself and move around on your own.

One of the things I'd still like to accomplish in my lifetime, is finding a methodology so blind people can compost and garden better. I'm hoping that this website will lead to locating some assistance to help do that.

Unless you do nothing to it, what you plant in, should be called soil, unless it was disturbed to begin with.
Just so the soil science community doesn't think I'm competing with them.

This message is limited to defining what ROI (my company) calls dirt. Not what anybody else calls it. It is absolutely not important to me that anyone else agrees with the way I define dirt.
Maybe based on my definition, somebody will come up with a better one? I'm all for that...

And before anybody gets to asking lots of questions - yes, I can perform a multitude of tests on any growing medium.
I know how to test for C:N; plant nutrients, humus, organic content, pH, etc., etc., etc. I can read and understand Soil Surveys and have read all about the properties and classification of soils, from Alfisols to Vertisols, and more.

But what we will discuss from this point forward is good 'ol DIRT. As a growing medium for plants. Not as what the earth is made of, or how old dirt is.

There are a lot of attributes of quality dirt.
Having some mineral in dirt won't hurt it, as long as the mineral isn't salty or makes dirt way off-balance, pH-wise.

Since what you have for earth wherever you live - is what you have - that's where you need to start - by finding out what it is you have - that you call land. Ground. Earth. The piece you own or have permission to garden in.

That means you should send in a Routine Soil Test sample to your state's land grant university, to obtain a laboratory analysis of your soil to find out what it does have and does not have, and what the soil lab folks think it needs. But don't believe everything you read...

If you can afford the extra $5, recommend that you ask for a reading of micronutrients too.
For another $5 you can get a reading on the percentage of organic MATTER in your soil. A reading of organic MATERIAL is worthless.

So what I'm set to do via my website is help people to understand how to make and use DIRT. Not soil.
In my book, there are three classes of dirt, based on the percentage of organic material. Because these three categories act differently when growing certain kinds of plants, retaining water and nutrients, etc. We'll get to all that later...

  • 1. Plain Dirt - less than 3% organic matter
  • 2. Skinny Dirt - 3% to 6.99% organic matter
  • 3. Fat Dirt - 7%+ organic matter

Now let's take a moment for me to be contentious again.
Cornell University at: makes some statements that need to be noted. And normally I wouldn't fuss about this, but it is a lab course, so it is what Cornell is teaching folks.

In that document under "A. Analyzing Soil Physical Conditions" it begins: "The soilís bulk density (Db) is the ratio of the mass of dry soil to the volume of soil. They say that the higher the bulk density, the less pore space a soil has.

Then, regarding BULK DENSITY (Db) it states: "Bulk densities for organic soils, such as uncultivated forest and grasslands range from 0.1 to 1.1 Mg/m3. In cultivated soils, values range from 0.9 to 1.8 Mg/m3. Bulk densities higher than 1.6 Mg/m3 inhibit root penetration. Usually values greater than 1.7 to 1.9 Mg/m3 indicate a fragipan or a compacted glacial till layer."

Then a couple of paragraphs farther down regarding PARTICLE DENSITY (Dp) it states: "The mineral crystal structure and the chemical composition of the soil determine particle density. Therefore, the range in most mineral soils is smaller between 2.60 to 2.75 Mg/m3. Organic soils have a lower particle density since organic matter has a density of .8 Mg/m3.
For calculation purposes, a particle density of 2.65 Mg/m3 is assumed for mineral surface soils with organic matter between 1 to 5 percent.

WHOA, hossie... First, I don't agree with the Cornell "number-crunching. Secondly, there is a LOT of difference between a mineral soil with 1% organic matter, and 5% organic matter, and a soil with more (5%) organic matter DOES NOT INHIBIT ROOT PENETRATION - and to specify an 'average' particle density for a 1% to 5% spread? Sheesh, where do some of these soil 'scientist' come up with such radical ASSUMPTIONS? As soon as is practical, you can bet that I'll address these issues in a separate document with the correct statistical data.

Anyway, Fat dirt is the goal for an organic gardener, and the fatter the better, so long as aeration and percolation are maintained. Do not walk where you plant, since compressing dirt is bad for it.

Plain Dirt can produce OK vegetable harvests, but the higher percentages of organic material in 'Skinny' dirt ensure that a sustainable source of plant nutrients are available, and 'Fat' dirt is right the on track.

Sustainability in multiple aspects (microbe diversity, available nutrition, pest resistance, disease resistance, etc.), is the target, and to some extent the TYPE OF CROP grown determines how much nutrition is extracted into the plant - that needs to be replaced in the dirt - in addition to increasing the available nutrients beyond what they were before planting the crop.

Dirt with less than 3% organic matter is OK for starters, but is not plant-sustainable in the long term because OM continues to decompose until (if) it becomes humus (by actual scientific definition which means that microbes are no longer able to decompose it). Humus does not mean 'organic matter' - contrary to use of that word on so many bags of what is commonly pawned-off to consumers as 'compost'. Not.

So - the main objective is sustainability of plants by microbes in dirt, is utilizing decomposing organic matter (OM) as food, to produce the nutrients, enzymes, etc. that plants need to be healthy and maximize harvests of beauty and food for humans and other animals, birds, butterflies, etc. in full the cycles of nature.

If your dirt has a high enough organic material content and has developed a diversity of microbial and 'decomposer' life, your dirt will have sustainable nutrition for plants. How high of a level of nutrition, will depend on how long a diversity of microbe populations can survive on the amount of organic matter provided.

Remember that in agricultural practices, the depth of "cultivated" land is usually estimated from 6" to 12", and the recommened depth for taking Extension Service soil samples is not very deep. But organic gardeners don't think that shallow(ly). How deep do the roots of the plants you grow, extend down? It's the ROOT DEPTH that you want to be concerned with, not the depth of a danged PLOW or DISC. Try NOT to think like an Ag. Agent or a soil gardener.

Every time you plant a crop, and pull up an annual plant after harvest, to compost it - a mass of roots are left in the dirt to add to the (dead) organic material content, that will become decomposed organic matter to feed microbes. And when you add compost, you are strengthening the microbial population in your dirt, and also as the mulch (on planting beds) decomposes.

If you grow enough, and pull a lot of annual plants, or have trees with fallen leaves, and especially if you have (or can borrow) a shredding machine, you should always have plenty of compost feedstock and mulch. If you're short any of those, you won't be very long, if you just 'ask around' enough. There's plenty of organic material in any community - it's just a matter of locating and transporting it back to your plants.

Never let your dirt dry out. The more organic matter that's farther down in the dirt, the less chance that plants will ever be stressed from too little moisture. One of the biggest issues with getting great harvests is IRREGULAR quantity of water available to roots.

And don't water with chlorinated city water (that kills microbes) if you can possibly avoid it. If city water is all you have, at least use a dissipation barrel or an activated charcoal filter on your watering hose.

If you have a roof, and/or space to collect rainwater runoff in a small catchment pond...That's a really good practice. A raised 55-gallon barrel even half full of water will produce irrigation through a spigot-fed soaker hose or drip irrigation line. It's not likely that your grandparents had hoses to water their garden from the well or cistern, and it wouldn't hurt you to learn how to effectively water plants with a bucket by making a berm.

All good dirt has porosity to hold air by virtue of organic material (bulk) content, and provide drainage that plants need to THRIVE - not just survive.
Good dirt is all about BALANCE.
Mother Nature works really hard to balance whatever additional organics you do add to dirt. Microbes are like that.
Making dirt means you are working within Mother Nature's system. 'She' really does know what she's doing. Better than soil scientists.
And nobody knows 'the answers' yet, about how Mother Nature (MN) makes humus from organic matter, with microbes. But at least we know 'she' does do it, and there's lots of people working on learning how 'she' does it. I hope we never do.
So some commercial company cannot make a bundle of money by replicating it synthetically, to screw-up the earth's crust some more.

You can trust Mother Nature to know what to do, with the dirt 'recipe' that you put together. After all, she made the soil too.
Recipes for dirt are discussed in later modules.

© 2010 Robert C. Moore ~ All Rights Reserved

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