What the heck is Humus?

Just to protect Mr Kempf's good name, he was explaining what you would get if you purchased a liquid labeled humic acid. I don't think his company produces humic or fulvic acid and he doesn't seem to advocate it's use.

The question that is coming up for me is this,  if humus is the remains after complete decomposition, what differentiates it from mineral ions?

My impression is that humus is composed of mix polysaccharides and glycoproteins. It is not true that all the "organic matter" is gone if what you mean is carbon (that's what "organic" means to a chemist). Lignin, for instance is made up of very mixed, very complex polysaccharides. Lignin doesn't have a single chemical formula. It is more like something generated by a regular expression, like language. A molecule could be branches and each branch consisting of a stretch of amino acids, a stretch of linked sugar, modified amino acids, alcohols. There is carbon in the amino aids and sugar, but it is very hard to break down. When I was in biochemistry I couldn't figure out how the amount of cellulose was quantitated in a sample mentioned in a scientific article. I traced back through back reference after back reference and finally established that cellulose was measured as what is left after you degrade everything else. These days there are enzymes (cellulases) that can degrade cellulose but if humus is a mixed molecule then a
cellulase won't be able to degrade much of humus.

Its starting to sound like humus is more of a transitory state within a particular system, than a particular thing. Maybe I'm not understanding the chemistry involved. Would it be in the same category as whirlpools - a observable thing that is an effect of momentum and not the water, algae and leaves within it?  

Well everything is temporary. Humus sticks around longer than a whirlpool where the same water molecules are temporarily rearranged. It is more that the complexity-  the randomness/diversity of molecular structure that , in a certain time frame, defies
breakdown. Various enzymes must chance upon the molecular bonds in order to attack whatever is at a free end of a complex molecule; a peptidase, then a cellulase or other polysaccharidase. The mixed molecules comprising humus do slowly break down into much smaller molecules but this is reflected in a change in the chemical covalent bonds.

BeverlyR Seavey wrote:Well everything is temporary. Humus sticks around longer than a whirlpool where the same water molecules are temporarily rearranged. It is more that the complexity-  the randomness/diversity of molecular structure that , in a certain time frame, defies
breakdown. Various enzymes must chance upon the molecular bonds in order to attack whatever is at a free end of a complex molecule; a peptidase, then a cellulase or other polysaccharidase. The mixed molecules comprising humus do slowly break down into much smaller molecules but this is reflected in a change in the chemical covalent bonds.

What do you think the molecular structure of humus is? My understanding is that it is, like lignin, it isn't a set structure and it's this dynamic character that makes humus so persistent

Yes- that is pretty much my impression but I am sort of guessing. The academic article referenced above, Nature volume 478, pages49–56 (2011), seems to suggest otherwise - that there are smaller molecules. If your public library carries JSTOR you can take a look at the article - no need to do a David Schwartz. My impression is that the smaller molecules are breakdown products of the larger complex, highly varied molecules. Remember that the humus sample is a snapshot of the degradation process - different molecules in the population are at different stages. It might be that it all breaks down to small molecules ultimately.

So... what is compost?

HAAAA sorry just kidding... I can be so annoying...

Hi All,

I recently wrote a blog post on this very subject which included a video of Michael Meléndrez, an expert on humus, explaining what it is. I think you all will find this intriguing, especially the intelligence factor. Here is the link to the post: https://learningtoliveandlovegodsway.com/2019/07/13/loving-the-soil-part-1-the-importance-of-humus-carbon-matrix/

Many of you will not enjoy the first 6 paragraphs of the article, but after that, I think you will appreciate what I have written. And you are also welcome to just skip to the video on humus at the end, which, I think is fascinating.

Cheers,
Jennifer

Bryant, thank you for this thread. I have to say I find some of what you've said confusing, particularly

"If you want to find humus you have to look for it in a laboratory setting since out in nature it disappears almost as quickly as it forms.
... Once humus is created, it immediately binds with those molecules and atoms that make up the inorganic parts of soil at that instant, humus is gone."

I am not a soil scientist myself but I've been attending conferences and classes and reading on the subject for over a decade, and what you said above seems to fly in the face of other definitions that humus is the most stable form of organic matter and can last for centuries. Your assertion that humus is not organic matter because the organic matter has decayed away is nonsensical, since organic matter is defined as being created by life processes, and decay is a life process. If decay were what created humus, then humus would by definition be organic matter.

However, I've attended half a dozen lectures and classes by Dr. Christine Jones (amazingcarbon.com) who discovered what she calls the "Liquid Carbon Pathway," namely that humus is formed exclusively in the presence of plant root exudates and not from decaying organic matter. She did an experiment that, as I recall, involved radioactive carbon in the form of CO2 that got absorbed by living plants and passed by them into the soil, but when those radioactive plants were cut down and placed in a chamber with fresh soil and no living plants, the radioactive CO2 went back into the air as the plants decayed and not into the soil. Unfortunately I'm not able to find a description of this experiment to cite; I just remember it from her lecture.

She likened humus to a house that is built intentionally by microbes for storing nutrients and for living in; far from being "gone" when it binds with nutrients, that is when it fulfills its function. It is a product of decay only in the same sense that a stick-frame house is a product of the decay of forests! Yes, the trees break down into lumber before they reassemble into houses, but it's not a passive decay process, it's an intentional construction process. Being like a house, there is no precise chemical formula for building humus, just a general specification that can be met by thousands of different arrangements of chemicals.

The microbes that build humus can also live in the honeycomb structure of biochar, which is why adding biochar to soil (along with living plants and their microbiomes) causes an increase in humus: the microbes live in the biochar temporarily while they are constructing humus to live in long-term.

In more recent lectures Dr. Jones has advocated preserving organic matter with anaerobic lactobacillus fermentation (basically making silage) instead of aerobic composting, so that the carbon stays in the soil until plants' microbiomes can convert it to humus and other stable compounds, rather than escaping into the atmosphere.

I agree that there is a lot of misinformation about humus, and I admit I may be repeating some myself, but I suspect you are not immune from this either. Thank you again for the conversation.

Ben Stallings
PDC instructor
Kansas Permaculture Institute

Such a fascinating topic/thread - many thanks for the insights.

My query is how does a substance like comfrey tea relate to humus? And also I am experimenting with a hot compost bin where the leachate can be drained off periodically - similar question, how does this leachate relate to humus?

Hi, Chris. If Dr. Jones is correct that humus is only created by the plant microbiome, then a "tea" made from plant leaves is unlikely to contain any humus. However, it can be rich in nutrients, fiber (prebiotics) and microbes (probiotics) that will assist in humus production once it's back in the soil.

And if Bryant's friends are correct that humus is insoluble, then it's unlikely that aerated compost tea, worm "juice," or anaerobic compost extract contains humus either, just because an insoluble substance by definition won't dissolve in water. But they can still be great for stimulating the soil life that will create more humus.

I use liquid carbon 24% made from Reed Sedge Peat when making a biological cultural to treat manure pits and have noticed that the biology in the culture will use the carbon as a food source until I place the culture into a pit.  Since I have increased the rate of carbon in the mix, the culture once in the manure pit really takes off in digesting the manure.    If there is an issue with crusting on the pit, I will have the barn owner spread dry Reed Sedge Peat down through the slats to the top of the crusted manure and this will help reduce the crust over time.   My question is this, do you think that the carbon in the Reed Sedge Peat that is working with the biology in the pit would eventually create some humus when given enough time?  And would that humus bind with the nutrients in the manure to create a stable compost loaded with nutrients that are more soil friendly.  

Hi, David. If Dr. Jones is correct that humus is only created in the presence of living plant roots, then you would need living plants in the manure pit in order to create humus there. Is that the case?

s. lowe wrote:Just to protect Mr Kempf's good name, he was explaining what you would get if you purchased a liquid labeled humic acid. I don't think his company produces humic or fulvic acid and he doesn't seem to advocate it's use.

The question that is coming up for me is this,  if humus is the remains after complete decomposition, what differentiates it from mineral ions?

No need to "protect Mr. Kempf's good name, he is a remarkable scientist and I have nothing but respect for him and his work.

Now it would seem that I need to make the statement "just because we have a current definition doesn't mean that a new, more accurate one won't come along in the future".
Much of the research, such as Dr. Jones' work seems to point out that nature loves diversity in every thing. Which is my POV as well.
The problem with using the word "Humus" is that so many "experts" (including me) have used it incorrectly because there are so many ways humus can be misrepresented and has been misrepresented in class rooms, white papers and even in lectures meant for laypersons.
The single most prolific misrepresentations come from "Garden TV show hosts", just about every one where humus is mentioned uses the term in the wrong context and thus the error continues.

Humus, by current accepted definition is what is left after organic matter has completely decomposed.
That means that humus isn't "organic matter" it is what is left once all the organic matter has decomposed (gone away as it were).
Or it means that we don't really know what organic matter is.
This also depends on chemistry, which considers any compound with a carbon atom as being organic, which is a science truth.
(science truth means it has been tested over and over with the results coming to the same conclusion, in math it's a "law").

Since Carbon must be present for a molecule to be considered organic, when the carbon leaves or is simply broken away from any molecule, it isn't "organic" anymore.
If you take any molecule and get a carbon atom to bond to that molecule, then it becomes organic as soon as the carbon atom bonds.
Since the current definition of Humus states that it is what is left from the complete break down of organic matter, it is plausible to determine if the carbon atom broke free and gassed off.
If that happened, then the material doesn't meet the definition of organic matter any longer, according to scientific definition.

In science we like to have concrete evidence that is repeatable, without repeatability the conclusions are still theory and sometimes theory is misconstrued (usually by the press in my experience) as truth or fact when it hasn't met the complete set of rules for theory becoming law or fact.


Redhawk

To Ben  the answer is that there is no living plant roots in these manure pits.  So the living plant root is providing a way to photosynthesis in order to create the necessary condition, chemical transaction, or other unknown needs to make the humus?  

David Widman wrote:So the living plant root is providing a way to photosynthesis in order to create the necessary condition, chemical transaction, or other unknown needs to make the humus?  

If I understand Dr. Jones's research correctly, the microbes that build humus do so only when they are being fed exudates (sugars, carbohydrates, and simple proteins) by plant roots. In the absence of plant roots those microbes don't live and so don't build humus. That doesn't mean the manure compost can't be a nutrient-rich soil amendment, it's just not humus per se.

Bryant, I would ask you to consider the "humus is a house" analogy again. Suppose an alien watched the construction of a stick-frame house from a series of snapshots taken from orbit. First there are trees standing. Then there are logs (decomposing organic matter). Then there is milled lumber (further decomposed organic matter). The stick frame disappears from view as the roof and siding are put on the house. Finally, after all the lumber is cleared away from the site, what remains is the house. Meticulous scans of the site reveal no trees or lumber remaining in view. Should the alien conclude that the house is not organic matter, since it is what was left after all the trees and logs and lumber were cleared away? Or should it conclude instead that the house has been made out of lumber, and that's why lumber is no longer visible?

It is my understanding that humus is made out of organic matter just as the house is. While the initial steps in its formation are decomposition, the final steps are construction. The reason humus fails some chemical tests for organic matter is not because the organic matter is absent, but because it's been built into a form that is stable and not chemically reactive.

If you think humus does not contain carbon, I would question why it is black (like charcoal) and why it burns (like charcoal).

Oh what a mistake I've made.  It seemed, that with all the diverse opinions expressed, that for clarity it would be wise to review again the definition of humus. In doing so I may have discovered the problem. According to the first 12-15 definitions provided by Mr. Google, no two were the same. There are some from Webster, from linguists, some local, some international, others from scientific journals, others from myriad "experts" and groups. Some say brown, some black, some black and brown, some wet, some dry, some arobic, some anaerobic, some equal to compost, or partial compost, or finished compost, or finished aged compost, or absolutely NOT compost, or plant based only, or plant and animal based, or it does not exist at all, or it lasts for eternity. In some cases it exists only in the presence of live plant roots, others say its found deep in pits. So, although I may be 100 IQ points short of understanding, I'm back to Mysterious, Magical, Molecular Poo. And, I love how it makes my tomatoes and peppers taste.

To Ben   Thank you for answering my question  on what it takes for the microbes to make humus.  I feel that the health of the soil is highly dependent on the nutrient cycling of the microbes in the soil working with the plants.  The goal of treating manure is to reduce the toxic gases produced when manure breaks down and hold more nutrients in the liquid to be transferred to the soil.  As for "What the heck is Humius" from what I have read, it sounds like a very fast changing component of the soil biosphere that ends and starts constantly.  Blessings

Since there are now several "challenges" to this post, it becomes a question to me if those people read and understood my opening.

In my world of microbiology, when we talk about Humus there are two camps that jump up and shout their theories to the rafters.
The problem is that both camps are right, but they are talking apples and oranges (or mangos and walnuts if you prefer).
The problem is the accepted definition of Humus, which is:
Humus is dark, organic material that forms in soil when plant and animal matter decays.

When plants drop leaves, twigs, and other material to the ground, it piles up. This material is called leaf litter.
When animals die, their remains add to the litter. Over time, all this litter decomposes.
This means it decays, or breaks down, into its most basic chemical elements.

The definition is from the Oxford dictionary and Webster's dictionary.
Apparently there are some good folks thinking (which I always encourage) that I am some how in disagreement with a few other scientist.
Or they are simply taking one persons research and thinking they must be right, because they say they are.
I've never said I was the sole authority and I never would because there is no such thing in science, unless it is published that it is now a law of science, and that has never happened to me.

Questions: If roots need to be living in order for Humus to be formed, how is it that humus can be found coming from compost with no living roots in that compost or under it?
When we take one persons thoughts or paper as the only truth out there, what does that say about the one taking the words of another as written in stone?
If humus last almost forever or something that lasts hundreds of years, why is so hard to locate places that have loads of it?

Note: we have, on planet earth 1% of the land surface that contains Histosols, not a large enough quantity to be of great value farming wise.
Histosol: are soils without permafrost that are predominately composed of organic materials in various stages of decomposition.
They generally consist of at least half organic materials (by volume).
They are usually saturated with water which creates anaerobic conditions and causes organic matter accumulation at rates faster than that of decomposition.  
Little soil profile development is present, due to their saturated and anaerobic condition, however layering of organic materials is common.
Histosols can form in wetland areas of any climate where plants can grow such as bogs, marshes, and swamps, but are most commonly formed in cool climates.
Humus must be part of this sort of soil or at least it would seem so. Yet, humus isn't mentioned as being part of the histosol profile. (Which I find very interesting)

I'll be back with more on humus, but right now I am not feeling so hot, so it might be a while before I come back to humus.
I can almost guarantee that the end of this thread will cause head scratching at the least.

Thank you for clarifying, Bryant. I had thought given the question in the topic of the thread that you were asking what humus was or that you were unclear about it. I now understand that you intended to use the thread inform us of your views on the topic, so I will look forward to hearing the rest of what you have to say.

Bryant RedHawk wrote:Since there are now several "challenges" to this post, it becomes a question to me if those people read and understood my opening.

In my world of microbiology, when we talk about Humus there are two camps that jump up and shout their theories to the rafters.
The problem is that both camps are right, but they are talking apples and oranges (or mangos and walnuts if you prefer).
The problem is the accepted definition of Humus, which is:
Humus is dark, organic material that forms in soil when plant and animal matter decays.

When plants drop leaves, twigs, and other material to the ground, it piles up. This material is called leaf litter.
When animals die, their remains add to the litter. Over time, all this litter decomposes.
This means it decays, or breaks down, into its most basic chemical elements.

The definition is from the Oxford dictionary and Webster's dictionary.
Apparently there are some good folks thinking (which I always encourage) that I am some how in disagreement with a few other scientist.
Or they are simply taking one persons research and thinking they must be right, because they say they are.
I've never said I was the sole authority and I never would because there is no such thing in science, unless it is published that it is now a law of science, and that has never happened to me.

Questions: If roots need to be living in order for Humus to be formed, how is it that humus can be found coming from compost with no living roots in that compost or under it?
When we take one persons thoughts or paper as the only truth out there, what does that say about the one taking the words of another as written in stone?
If humus last almost forever or something that lasts hundreds of years, why is so hard to locate places that have loads of it?

Note: we have, on planet earth 1% of the land surface that contains Histosols, not a large enough quantity to be of great value farming wise.
Histosol: are soils without permafrost that are predominately composed of organic materials in various stages of decomposition.
They generally consist of at least half organic materials (by volume).
They are usually saturated with water which creates anaerobic conditions and causes organic matter accumulation at rates faster than that of decomposition.  
Little soil profile development is present, due to their saturated and anaerobic condition, however layering of organic materials is common.
Histosols can form in wetland areas of any climate where plants can grow such as bogs, marshes, and swamps, but are most commonly formed in cool climates.
Humus must be part of this sort of soil or at least it would seem so. Yet, humus isn't mentioned as being part of the histosol profile. (Which I find very interesting)

I'll be back with more on humus, but right now I am not feeling so hot, so it might be a while before I come back to humus.
I can almost guarantee that the end of this thread will cause head scratching at the least.

The first question that comes to mind for me, reading this post as well as thinking about this broader thread and topic, is ; do we need a new, more accurate, definition of humus? Is it possible that we are narrowing in on a concept that was poorly defined in the past when it was first formally identified in our modern age? If we think the working definition of humus is proper and should be kept and explored, then I would like to propose forming a definition for the other thing that we seem to be talking about in this thread. What should we call this amorphous substance that seems to be definitely organic, capable of being created by some sort of stalled decomposition, and be widely considered positive as an addition to living soil systems?

And Dr. Redhawk, I am stuck on the issue of; what separates the conventional definition you have outlined of 'humus' from 'mineral ions'? It seems that in the mineral theory of biochemistry there is nothing but ionic mineral forms left following organic decomposition and that is what makes compost, worm castings, and green manure cover crops so valuable for agriculture, they all create ionic mineral molecules that are available to our target plants. If humus is something outside of this realm then I think the value of understanding what, exactly, it is will be hard to measure. And if humus falls within that 'naturally ionized mineral' realm than I'd like to redouble my call for describing and naming that transient and yet stable organic soil formation that seems to thrive on finished compost, living roots, and 'full' decomposition.  

So we have many different ideas of what humus is, and as is normally the case Humic acid comes into every discussion about humus.
What we know about humic acid is that while it does exist, it is a fleeting thing, very similar to the electron charge differences we can find and measure in a water vortex, it exists but it is very hard to hold or see it.
Humus, while it would seem easier to locate and study, manages to elude those who are trying to quantify what humus is made up of.
This leads researchers to wonder how so many companies are marketing "Humus and Humic acid' how do they do this when the scientific community shows that the jury is still out on the issue of what humus is as well as what humic acid is.
The scientific community is hesitant simply because there is no consensus on a better definition at this point.
This can lead to confusion by all involved and especially for those who just want to be able to get their hands on the magical stuff that powers all life on planet earth.  
It reminds me of "Catch 22" because it fits perfectly into that movies premise "I'm crazy", "no you can't be crazy, because you think you are crazy, if you were crazy you wouldn't know or think you were crazy".

What this leads us to is a lengthy description of what humus is, not where we can find it (because it nearly instantly becomes a part of soil particles, and how do you find a substance that has fully incorporated into new compounds).
We know (Know = mostly certain or completely certain):
That humus is organic, what we need to discover is whether or not it is still organic matter since that is where it originates (from the complete decay of organic matter comes humus).
We know that many organic substances have been and are being touted as HUMUS and being packaged and sold as such.
We know that Humus, is very difficult to locate since it seems to disappear almost as it is formed by bonding with elements of the soil.
We know that Humus is so key to life that it can be considered a keystone element of life on planet earth, especially for land based animals, insects, etc.
We know that the main form of humus is liquid which makes it easy for it to soak into the soil below the heap of organic matter that spawned the creation of the humus.
We know that once the liquid humus has soaked into the soil, we can no longer find the material, it appears to change from the form of humus into other compounds, carbon rich and so considered organic even though the carbon found is bound to other elements (chemical and mineral in compositon).
We know almost the same amount of information about humic acid, except that we can only find humic acid in a lab setting since it too seems to instantly change makeup and properties as soon as it touches soil or dirt.

Perhaps our real questions need to be what does humus and or humic acid do for soil and plants?
Then it effects organisms that make use of those plant materials as a food source but what does it do?
How much of this magic substance do we really need in our soils that we grow our food stuffs in?
How can we get more Humus into our soil if that is what we need to do?

Currently we know we need humus in soils for completion of the circle of life mechanisms.
We also know that without the presence of humus in our soil, we wouldn't be able to grow much of anything of great nutritional value to humans or any other animals.
We also know that even the oceans are dependent upon the washed to the sea soil (now called sediment because of where that soil has ended up).
(You can simply substitute humic acid for humus in the above passages if you are wanting to study humic acid)

Humus is raw organic matter, broken down into the constituent parts of what formed the organic matter. (my own definition)
Humus if formed as organic matter breaks down through the processes of decomposition, it contains enzymes left over from the bacteria and fungi doing their job of recycling, it contains carbon atoms and atoms of all the other "parts" that make up any living organism.
Humus is not humus unless there are parts from animals decaying included in the organic matter that decays so that humus can form.
Humus does not need working into the soil, it will do that all on its own and almost as quickly as it makes its way to the dirt or soil below it.
Humic acid forms at the same time that humus forms and it reacts in many of the same ways as humus, including disappearing almost as fast as it forms.
Humic acid disappears because it forms new molecular bonds with ions it comes in contact with and that changes it from humus to something else entirely.

Pertinent questions that come up when Humus is the topic of discussion around the table.
How can we create humus or humic materials so that we know they are present?
Since we know that humus is readily incorporated into microorganism rich soils as well as in microorganism poor soils, how does this mechanism actually work/occur?
What do the plant exudates tell the microbiome to do with the raw forms of nitrogen they can break down (ammonia, ammonium and all the various ammonia compounds)?
What methods work best for collecting humus just as it is being formed so we can examine the molecular structures of this material?
How many elements will humus contain? What elements does humus contain? How can we best collect humic acid for testing purposes?

This list could go on for quite a while, since we might want to break humus down into each individual element to find out quantities and molecular bonds formed between each of the elements that make up humus.
The single most important thing about humus, that causes so much confusion amongst those of us who study items like humus is; since the stuff doesn't hang around in the form we want to study, it is difficult to come to good conclusions.

For us, the gardeners and farmers, the most important thing to know is that humus is a requirement for having nutrient rich soils to grow food items in.
We can create pockets of humus containing soil simply by piling up organic materials and inducing them to rot away.
Humus is transient by its very nature, so even if we can't hold it, see it or otherwise touch it, it exists and we want to have it.
The microbiome seems to be set up for taking advantage of humus being present, but it can and will create it if there isn't any already present.
Plant exudates seem to also be a part of the humus picture, since many of the helper organisms plants call on for nutrients are also the makers of humus.

You might gather from this post that lots is going on in the study of humus and humic acids, which is a good thing, since it is a major topic in some science circles and has been for at least two decades.

The best method for installing humus into your soil is via complete decay of organic materials heaped up on the spaces you want to add humus or humic acid.
This method makes sure that what you want (the humus) is capable of getting into the soil right where you want it.
By using "composting heaps" you not only get humus seeping down, you also get the humic acid flowing in the same places.
All that goodness for the soil, installed right where you want it, has to be the best thing ever for your gardens.
It is also a great thing for your health since humus creates healthy soils and thriving microbiomes that are full of microbes we want in our soil.

Redhawk

Humus sounds a little like love.  
1. It makes the world go around.  
2. The word vaguely defined, but is desirable, so it is constantly misused by marketing.
3. Hard to define precisely, but we pretty much universally recognize its existance.
4.  We have ideas how to grow it, but it's hard to measure.
5.  We can recognize it by its effects on existing systems.

Maybe, like love, there is an aspect of it that science is ill-equiped to measure (at this point).  Maybe we need to be looking for the secondary effects as evidence, rather than the basic properties.  (We know it must be there because these things are happening.)

Like love, the real question is "how can I get more?"  You have addressed that question, in general terms.

How Humic Substances Reduce the Need for Nitrogen

https://m.youtube.com/watch?v=CAOUTyrWzGU

Dr RedHawk,

I have heard that many now say that there is NO SUCH THING AS HUMUS in the scientific world.

This is mainly because over a hundred years  ago when they say they discovered "HUMUS" it was only after adding very alkaline (13pH) to even be able to extract the organic substances out of the soil. To make humic acid and other humic compounds you must add this high alkaline compounds to form them. From my understanding is that at this high pH that then strange chemical & weird reactions take place. Nobody could say for sure that the humus in soil was the same humus being studied after extraction. I'm not saying that humic acid and humic compounds don't help soil, but what I'm saying is that what we call humus and humic compounds may not be what was made naturally and now what we are calling humus could be man made chemical compounds that if your trying to then "BE ORGANIC" then by definition you are actually NOT being ORGANIC by adding such man made chemicals. I know I'm being devil's advocate. But the more I researched this topic the more I think that just adding naturally made humus (such as natural deposits in the deserts in USA, or naturally made in compost or vermicucomposting may be better and truly organic not just a man made chemical compound that is wrongly called "ORGANIC"....

hau C Rogers, Humus is one of those "great debate" items around a table of scientist. I was part of one of those discussions several years ago which got my interest up in finding out more about the whole process that leads to what has been termed humic soil.

The problem with humus and humic acid is that both are fleeting when it comes to how long can we actually find these substances, it is perhaps milliseconds at best since these compounds are almost instantly incorporated into new compounds.
Humus seems to be formed by bacterial actions via their enzymes and then it is recombined by those very same enzymatic actions of bacteria, same goes for humic acid.
This makes the real problem of proof nearly impossible with the current technologies we use for finding such compounds. This is very much like trying to prove that a vortex can make "super water", the conditions have to be right and you have milliseconds to locate it, then it is gone.

The best method, so far, for being able to quantitatively show that humus exist is to build a compost heap that includes animal parts, there is a correlation between the non plant proteins and collagens and the formation of humus, we can occasionally collect minute quantities of liquid from the leachate at the bottom of a well built compost heap, however once that liquid is acted upon by not only the bacteria and fungi but by simple contact with air, the compound we refer to as humus changes into many different new compounds which is what makes the soil below a compost heap so rich in organic matter.

The debate will continue until such time as we have the capabilities to capture and chemically test in the "real time" of humus existence.

In the mean time I think it is most important to build compost heaps, moving the heap location so that we can infuse the soil with all that organic liquid wonderfulness.

Redhawk

Dr. Redhawk,
In your opinion, what distinguishes these fleeting humic substances from simple ionic minerals formed biologically and in transition between beings in living soil/compost? Also, what role do you think that clay colloids play in the humus process? I have heard that stable humus compounds are formed when biologically ionized minerals are bound up with clay colloids forming a sort of dynamic but stable system. My understanding is that this arrangement does form in healthy soil, the debate seems to be whether this is 'humus' or if this is some other unnamed substance.

This discussion has made me think that the current formal definition of humus doesn't really have much of a use. While there is also this other soil phenomenon that is often called humus/humic but doesn't have a formal name that I'm aware of. That situation certainly makes me think that we would be best served by our language if we shifted the word humus from a theoretical and amorphous substance/phenomenon to the one denoted by the more colloquial usage.

Bryant RedHawk wrote:
The problem with humus and humic acid is that both are fleeting when it comes to how long can we actually find these substances, it is perhaps milliseconds at best since these compounds are almost instantly incorporated into new compounds.
Humus seems to be formed by bacterial actions via their enzymes and then it is recombined by those very same enzymatic actions of bacteria, same goes for humic acid.
This makes the real problem of proof nearly impossible with the current technologies we use for finding such compounds. This is very much like trying to prove that a vortex can make "super water", the conditions have to be right and you have milliseconds to locate it, then it is gone.

The best method, so far, for being able to quantitatively show that humus exist is to build a compost heap that includes animal parts, there is a correlation between the non plant proteins and collagens and the formation of humus, we can occasionally collect minute quantities of liquid from the leachate at the bottom of a well built compost heap, however once that liquid is acted upon by not only the bacteria and fungi but by simple contact with air, the compound we refer to as humus changes into many different new compounds which is what makes the soil below a compost heap so rich in organic matter.

The debate will continue until such time as we have the capabilities to capture and chemically test in the "real time" of humus existence.

In the mean time I think it is most important to build compost heaps, moving the heap location so that we can infuse the soil with all that organic liquid wonderfulness.

Redhawk

That is some of what I heard too (humic substances IF they exist, are when organic materials are broken down to simple, maximum amount of decomposition, but the problem is that the fungi, and bacteria besides breaking down larger molecules into smaller they also take small/simple molecules and make larger ones). So I agree that it is like an electron flying around an atom, it may be in this spot at this time, but a millisecond later its gone. My main concern is people who buy soil that is called humus and think they are buying something special, while in reality any good compost or vermicucompost will have humic compounds and probably be both cheaper and better than the so-called humic soil/ humus... As with much of organic things being sold today, there is no listing of whats actually "IN" many of these snake oil things people are selling only to make a buck on people jumping on the organic band wagon.

hau S. Lowe,

For me the distinguishing character is the carbon compounds, these are apparently bonds that aren't as easily broken as other compounds that contain carbon. The compounds are distinguishable by the number of carbon atoms contained in the molecule, most that remain after decomposition will have 4 to 8 carbons, those that had fewer seem to be the first to be broken down, some leave as gasses (CO2, CH4, C2H6 and other "simple" carbon compounds, then there are the nitrogen compounds such as NO2), sometimes carbolic acid will form and remain as well and I think part of what some call humic acid is a case of proper identification since some acids can and will transform when given the opportunity as in when the right minerals are present and in an ionic state.

Overall I stopped searching for humus and humic acids, the few times we could identify them, they didn't remain for more than a blink of an eye, having gathered electrons and becoming something else.
To me the only thing we need to know is that when we place a good sized compost heap directly on the soil surface and let the microbiome do what it loves to do, we end up with a soil that has properties we can not simply go locate out in nature unless we happen to sample the exact right spot.
Humus formation does seem to require animal proteins and collagens to form, part of that process is perhaps what happens with colloidal clays.
All molecules and atoms want to be stable and that means all the needed electrons, protons, etc. must be present and bonded in the right places so they are as stable as possible.

My current view is that we want stable molecules that are still capable of change when the right ions present themselves along with free carbon atoms, new "humic" molecules might form.
I think that if an undergrad wanted a huge challenge for their doctoral work, this would be a grand one, providing positive proof, either way, would be definitive to science and agriculture.

As I mentioned at the start of this thread, the definition is lacking specifics, and that has allowed "theories" to run rampant with some folks stating theory as fact, no matter if right or wrong.  

The black gooey substance of Humic acid sounds similar characteristically and in certain aspects of its origin to Sepp’s bone sauce. I am curious if there is any useful correlation.

Bryant RedHawk wrote:

Huxley Harter wrote:I used to think that humus was really nutrient rich organic matter that had no distinguishable plant or animal parts in it. Now it sounds like it's bare nutrients that haven't yet been taken up or secured by soil life.

Humus is organic material that has undergone complete decomposition, so complete that nothing of the original materials is distinguishable even under a microscope.
It is not "bare nutreints that haven't yet been taken up", it is a nutrient matrix that melds into the soil beneath. More specifically it is a nutrient matrix being re-used by new plants (circle of life).

Humus is how nature recycles plant and animal parts that have died and then fed the trillions of bacteria, fungi and all the other microorganisms of soil.
The nutrients could perhaps be construed as bare but they have been used to build plant parts and animal parts that are alive then died and are being recycled yet again.
However, grabbing a hand full is almost impossible since as it forms it melds into the soil it touches, virtually disappearing almost as soon as it forms.
Humic acid is even more fleeting in separate existence since it is liquid it seeps into the soil where it binds to particles of soil as soon as it touches them and this is such a complete binding you can't locate it except through chemical testing.

Hi Bryant and thanks for sharing all your knowledge.
If what you mention is the case, then what do you think about making the compost directly on the ground, then when it is ready removing whatever is left up to let's say 2 inches above original ground level and grow directly on those 2 inches? Since we watered the compost heap to keep it moist, that would have caused the humic acid to leach into the ground thus making it very fertile?

Thanks for your insights.

hau Nono, I like your idea and you could even leave as much as 6 inches should you want to do so, the bottom of a compost heap (those last few inches) are where you will find the humic materials and leaving that layer will be awesome for the plants you install.

Humic materials do wonderous things to the soil, they open structure, they provide nutrient flow, water infiltration, bioactivity increases too. The free carbon becomes part of the matrix so it is captured and that also is good for the microbiome we want to feed.
Humus also will open clay structures (clay will eventually look more like terra preta with enough humus added over a long period of time).

Redhawk

Bryant RedHawk wrote:Humus is very close to the substance or substances that allowed life to take hold on this planet. It is kin to that "Primordial soup" that the first bacteria sprang from, that is how much a  mystery humus is.
It consists of all the molecules and atoms that were part of the organic matter that was decayed to the point of not being even compost.
That means that it is comprised of minerals, proteins, carbohydrates, sugars and starches, all freed by decaying micro organisms then further refined by those organisms along with the worms and other macro organisms.
The bacteria tend to remain in and around the newly created humus, which makes it a compound containing more than just substances.
Humus also seems to be a solid liquid since compost can release some of it as a leachate but we are also supposed to be able to hold it in our hands, which I've personally never been able to accomplish.

This is pure soil poetry!

Humus is
crude oil
dark, organic material that forms in soil when plant and animal matter decays.
this could be used to describe crude oil also.  

Beau Davidson wrote:The black gooey substance of Humic acid sounds similar characteristically and in certain aspects of its origin to Sepp’s bone sauce. I am curious if there is any useful correlation.

I have made Sepp's bone sauce and since your question has gone and activated my working brain cells, I'll now have to make another batch and run some tests.

Redhawk

jimmy gallop wrote:Humus is
crude oil
dark, organic material that forms in soil when plant and animal matter decays.
this could be used to describe crude oil also.  

Really?

A rather sophomoric statement isn't it?
Crude oil forms under great pressure, humus doesn't form that way, Crude oil is formed only in anaerobic conditions, humus is only formed in aerobic conditions.

Redhawk

Whew. I started this wanting to know the difference between "humus" and "organic matter" and "compost" but I don't have basic understanding of chemistry and at this point the question of what humus is and does is starting to sound like it's located on the border between physics and theology. I don't care anymore. Let's get practical. I do have a question about soil: I collect the urine of my two family members, and use it on my 7 to 10 compost piles to speed decomposition. Some of these piles are in the woods, composed of rotting logs and branches, there is a pair above my garden, and then there is a pair of circular netting bins for leafmold; I run these over with lawnmower, or this year I'm using a borrowed leaf chopper, so it only takes one year for the leaves to decompose. Since I keep good records of my garden, I've found that the leafmold gives better results than compost, mostly. The question is, should I keep using urine on the leaf bins? And, sometimes grass gets in there--is that good, or should grass clippings be kept separate from molding leaves?
It's my opinion that the most exciting frontier in science is the study of soil ecosystems, study that yields useful knowledge.

hau Mary, How do you use your leaf mold? Most people use leaf mold as a top dressing (mulch) and this is where most of the real decomposition of leaf mold occurs.
Leaf mold (at least mine) tends to be lighter and "fluffier" than finished compost. Leaf mold is not a finished product of gardening (grass clippings are leaf matter so why not use it in leaf mold production?), it is faster to make and easier to use and it has lots of good things in it.
For me the difference between compost and leaf mold is the microbiome along with nutrients available.
Compost will have more items breaking down (leaves, twigs, sticks, bad fruits and vegetables, animal parts or whole animals in some cases, so there is more variation in "raw materials" going into compost than in Leaf Mold.
This difference does not make one better over the other, it is simply one of the main differences so we can keep them straight in our heads.

Since all of us have different needs in our gardens, each of us needs to find those items that work best for our situation and then stick with those as we trial and either discard or adopt other items that we think will work for us.
Gardening is not sans-active brain use, those that simply buy a book and follow what it teaches are most likely missing out on at least half of the fun of gardening and they are probably not getting the production they desired either.

Now about the why leaf mold generally works "better" than compost for lots of people.
Leaf Mold (LM) is partially decomposed prior to use as a mulching layer, that means the material is not as decomposed as compost, which means that the bacteria and fungi still have a lot of work to do to break down the LM into component parts.
This leads to higher activity by the members of the microbiome which leads to better spread of the organisms when applied around your plants to help hold water in the soil as well as provide soil coverage against erosion by rain fall or wind.
Your plants will send out exudates with signals to the microbiome with what the plant needs right now, the organisms of the microbiome then fill that "order" by breaking down the materials that contain those needed items or single item so the plant roots can suck it up.

Urine is called urine because the primary item is Urea which comes from several different chemical compounds including Uric acid, that is gathered from the blood stream by the kidneys along with some water and lots of other human body contaminants that are blood borne.
(farmers use a solid form which is called Urea and is for the most part just crystalized uric acid this breaks down into ammonia and ammonium by bacterial actions and then ammonium is further broken down so the plants can take it in and move it to the parts of the plant that need it).

Did that help you?

Redhawk
(if this didn't give you the information you desire, let me know and I'll try again).

Some of us read about it, some discuss it, some study it, some look at it, some debate it, some argue it, some meditate on it.
The real GOLD, well stated by Dr. Redhawk is
 "In the mean time I think it is most important to build compost heaps, moving the heap location so that we can infuse the soil with all that organic liquid wonderfulness."

The value is NIKE     "JUST DO IT!!!"  , keep up with the above interactions, but most importantly make a pile today.      k

Hi Bryant

Leaf mold (at least mine) tends to be lighter and "fluffier" than finished compost. Leaf mold is not a finished product of gardening (grass clippings are leaf matter so why not use it in leaf mold production?), it is faster to make and easier to use and it has lots of good things in it.
For me the difference between compost and leaf mold is the microbiome along with nutrients available.

I thought I had read somewhere that the difference between compost and leaf mould is the first is created  by (mainly?) bacterial decomposition, while the second is from (mainly?) fungal action. Is that right? and does it then make sense to mix/flex the use of them depending on how you see the needs of any particular area?

And a final question, I always thought that leaf mould was quite acidic as opposed to compost, and spend quite a bit of effort raiding my woodland floor to mulch those acid loving plants I have in the garden. Is that right, but does it make sense to mulch everywhere regardless? We have very heavy (subsoil type) clay, which is gradually being converted into better soil - not sure it will happen in my lifetime, but I will keep trying as long as I am able!

Best wishes, and many thanks for all your insights, much appreciated.
Chris