Introductory soil physics

[markyscott]

One thing I would think is that saturation zone goes up with coarse on the bottom so I would thing the saturation zone would go lower.
Love this thread. Well done and thanks.

Hi c54fun - that's the right idea, but it was fines migration that Davetree noticed. The fines moved down to the bottom of the cup with watering leaving the coarse grained fraction on top. Take a look at the picture again - see how much coarser the soil is on top of the cup than on the bottom? Stratification through fines migration would enhance the downward increase in water saturation resulting from gravity drainage. So even higher water saturations and lower AFP at the bottom of the pot than the top due to fines migration in a poorly sorted mixture.

So now we know. If we don't sieve we'll get higher water saturations and lower AFP overall. And due to fines migration we may end up with a more pronounced water saturation profile than we would otherwise expect.

Scott

 

[markyscott]

Scott,
While you at it. I understand Boon uses drainage layer and pass it down to all his students. As you have pointed out that layer raised the saturation zone instead of lower it. What is your personally practice on that. Do you use drainage layer or not?

Now that we've established some of the basic physics, let's return to this question and think about it more deeply. If a drainage layer really just keeps the soil more moist, does it have benefits? What are they and what factors should we take in consideration when we're repotting?

• For shallow pots it may not be such a good thing as these are already pretty wet - shortening them further by adding a drainage layer might further increase the water saturations after watering.
• For deep pots, (i.e. cascade pots) the top of a coarse soil may dry very quickly as gravity pulls the water toward the bottom of the pot. A drainage layer may help alleviate this effect
• For uneven pots where water pools on the bottom of the pot, a drainage layer can help keep the roots out of the puddles
• In all pots, a drainage layer allows oxygen access to the entire bottom of the potting mix and aids in the drying out of any areas of very high saturation that form due to incomplete gravity drainage
• As Owen mentioned, a drainage layer makes it easier to move a tree into a show pot while minimizing damage to the root system.

And remember. The words "shallow" and "deep" are relative terms. They're related to the kind of soil you're using. If you're using a fine grained or poorly sorted soil, "shallow" can be deeper than you think because the saturated zone at the bottom of the pot extends upward. So when I say "shallow", I mean "shallow relative to the saturated zone at the bottom of the pot". We want to keep plenty of growing area above this zone as water logged conditions will exist here for some time after watering. Too long in waterlogged conditions (<10% AFP) and plant growth can be adversely affected.

Scott

 

[Tieball]

This Would be a good in-depth article of information to go into Bonsainut Resources.

 

[markyscott]

This Would be a good in-depth article of information to go into Bonsainut Resources.

Thanks Tieball! I'll try and boil this down after this conversation has exhausted itself.

Scott

 

[markyscott]

...Lastly, I think this has been quickly touched on, but curious it's effect as well... some substrate obviously holds water better... Lava or pumice for example actually hold water within its pores and sometimes one will often find small feeder roots growing into these pores to obtain this. So, if you have a larger pot with more of this substrate, could you also say that the larger pot might as well retain more moisture? Verses a smaller pot with the same substrate? I guess what I am getting at, is do you think that this somehow changes this or keeps it the same?...

So let's go back to some of Stacy's questions. This is a good one because it helps me to bring up a new angle that I planned touching on in our discussion. I want to talk now about "dual porosity" systems. I know what you're thinking - "What the heck?" or "Did Scott forget his coffee this morning?" or "Exactly how many Shiners did Scott drink during Monday Night Football?". The answers are "Indeed", "On my second cup", and "None - I drank Dos Equis".

But back to dual porosity systems. The phrase refers to soil medium or geologic formations that have more than one population of pore sizes - like a population of large pores AND a population of small pores. There are lots of ways that this can happen in nature, but in a bonsai pot we're typically thinking about the difference between INTERgranular porosity (the pore spaces between the grains) vs INTRAgranular porosity (the pore spaces within the grains). This graphic will help:



See? There are large spaces between the grains (the intergranular porosity) while there are small pores within the grains (the intragranular porosity). Now that we've established the basic physics, we know what this means - if there are two populations of pore sizes, then there are two populations of water saturations as well. The large intergranular pores will have high AFP and low water saturation whereas the small intragranular pores will have low AFP and high water saturation. This is a good thing! It means we can have our Shiner and drink it too! Er, I mean have our cake and eat it too! We can have a high AFP (that the plants like), but store additional water in the micopores which will increase the humidity of the system for a longer period of time than we might otherwise expect.

Scott

 

[Anthony]

Our silica based gravel is most likely cemented together and not melted, then decayed material.

An idea, Marky is this possible ?
If so it carries water internally ?

Thanks for the lessons, Sifu 2
Good Day
Anthony

 

[markyscott]

More on dual porosity systems.

There are lots of different flavors of microporosity. Some will be more effective for our needs and some less. Let's take a close look at a couple of different varieties:



The picture on the left is a photograph of a piece of wood taken through a microscope. Look at all the microporosity in there! What you're looking at are the multitudnal units called cells which make up wood. I'm sure Osoyoung can tell us a lot more about this image, but the salient point for our discussion is that organics typically have a very high microporosity because of this structure.

But inorganics can have a high microporosity too. Take a look at the image on the right - that's a picture of a piece of pumice taken with a macro lens. Pumice is a naturally occuring rock that's erupted out of a volcano. It's erupted as a liquid (molten rock) that ascends very quickly through the earth. As it ascends, gas (water vapor, CO2, etc) evolves from the liquid and forms bubbles. Then when it erupts the liquid quenches forming a glass and preserving the bubbles - that's what all those holes are. Scoria (we call it lava rock) has the same thing. In fact the most often used defintion of scoria vs pumice is that pumice is less dense than water whereas scoria is more dense. That's all related to how many bubbles are in there. The spaces the bubbles formally occcupied are also intragranular porosity and can hold water the same as the cells in the piece of wood.

That's why different material - even if it's the exact same size and shape - will hold a different amount of water! But which is more important? The SIZE of the grain we use or the KIND of the grain we use? We'll get into that later when we get into the properties of some of the different soil components we have at our disposal.

Scott

 

[markyscott]

Our silica based gravel is most likely cemented together and not melted, then decayed material.

An idea, Marky is this possible ?
If so it carries water internally ?

Thanks for the lessons, Sifu 2
Good Day
Anthony

Sorry Anthony. I'm not sure I understand your question. Can you please clarify?

Scott

 

[Anthony]

Scott,

an older geologist down here put forward the idea that our white clay and silica based gravel [ used for concrete mixing as crushed material]
were formed in place.
Not as material deposited from the Orinocco. ultimately the source being the mountains of Venezuela.
Trindad has an igneous base, but was underwater for a long time and now carries heavy clay deposition, on most of the central and southern part
of the island. The north is a blend of rotten rock / stone, lots of folding, and limestone / shattered marble.

What I wondered was could our gravel be silica cemented together with alkalines and perhaps be porous as well.
Good Day
Anthony

 

[markyscott]

Scott,

an older geologist down here put forward the idea that our white clay and silica based gravel [ used for concrete mixing as crushed material]
were formed in place.
Not as material deposited from the Orinocco. ultimately the source being the mountains of Venezuela.
Trindad has an igneous base, but was underwater for a long time and now carries heavy clay deposition, on most of the central and southern part
of the island. The north is a blend of rotten rock / stone, lots of folding, and limestone / shattered marble.

What I wondered was could our gravel be silica cemented together with alkalines and perhaps be porous as well.
Good Day
Anthony

Got it. You might be interested to know that I'm a bit familiar with the geology of Trinidad and Venezuela and have done some field work near the town of Moruga, west of La Savanne, and around Naparima Hill.

A quick aside about the geology of northern Colombia and Venezuela (you have to forgive me while I turn into a geo-geek for a minute). It's pretty complex as there has been a lot of Tertiary faulting related to the Cenozoic eastward migration of the Barbados accetionary prism. Parts of Trinidad have been caught up in this deformation (like the El Pilar and Arima faults up in the north). The Arima fault is really important - it juxtaposes Jurassic and Cretaceous metamorphic rocks in the north with Miocene sediments further to the south. Those Miocene sediments are likely of Orinoco provenance whereas the metamorphic rocks exposed in the hills north of Port at Spain are probably not.

But back to your question. I think that you're noting that some of the material you're working with is a cemented sandstone or gravel. And you're wonder if the cements in the sediment can have microporosity as well. The answer is - maybe, but it depends on what kind of cement is present. There are three major cementing minerals in most rocks - a quartz cement, a carbonate cement, or a clay cement. Quartz and carbonate cements are not likely to have much microporosity whereas a clay cement might have a lot. However, cements are generally only a small percent of the overall rock volume (5% or so). So even if there is a lot of microporosity in the cementing phase it's unlikely to contribute significantly to the overall WHC of the soil medium when you use it as a component.

Scott

 

[Anthony]

Thank you very much Scott.
Turn geo-geekie as much as you wish. Yes, I was too lazy to ask a local geologist, because it is such dumb question.

After all of this, will there be soil mixes that feature solutions, I wonder about pots, lecca and colanders ?

Sits back down at his desk and looks at Sifu 2.
Good Day
Anthony

 

[markyscott]

So let's talk soil components. Again - I'm not going to tell you what to use. I don't care and none of my business, really. But at least I'll tell you what the heck they are - that I know something about. And it gives me the excuse to be geo-geekie again. I'll get the A word out of the way first.

What the heck is akadama anyway?

Akadama is a volcanic soil - it is composed of partially to completely altered tephra deposits of volcanic ash and pumice. It's parent material was from arc volcanics, probably andesitic in composition like those in the Cascades. Remnant pumice grains are apparent in several bags I've bought, but generally the pumice and ash are nearly completely altered.



The pictures you may have seen of the akadama mined in Japan have layers - a dark organic-rich layer on top, then the red akadama layer, then the yellow kanuma layer. The boundaries between these layers are called soil horizons. These kind of volcanic soils are called Andosols. An- is japanese for "dark" and -do meaning soil. It refers to the dark, humic rich upper layer of the soil. This layer is part of the definition of an andosol - it must occur within the upper 15cm of the groundsurface. So you should think of akadama as a soil, not a volcanic tephra deposit. It used to be many years ago, but that is mostly all gone now and replaced by clay minerals.



Scott

 

[markyscott]

More on akadama.

The alteration is interesting - with a lot of water, the ash breaks down to form allophane and imogolite, smectitic clay minerals that commonly occur together in an andosol. In fact, their occurrence is nearly diagnostic - andosols are pretty much the only kind of soil in which they are found.



There is an interesting pH control on the allophane-imogolite association, however. As pH changes, aluminum can combine with humic acid that leaches from the surface forming Al-humus complexes that can substitute for the allophane-imogolite clay minerals. At a certain pH, one becomes dominant over the other. So in a typical andosol, horizons form as a response to changing pH in the subsurface. This is what I suspect the akadama-kanuma horizon is. Akadama is dominated by allophane-imogolte clay minerals with subsidiary Al-humus complexes whereas kanuma is dominated by Al-humus complexes with subsidiary clay minerals.

I made this bold to get your attention - these organic complexes found within the clay are not found in any of the other soil components we use. I'm not saying its better or worse, but its certainly different.

Scott

 

[markyscott]

Last thing on akadama.

So where can you find this magic substance?

To replicate the conditions in Japan, you need 1)volcanoes, 2)a lot of rainfall, 3) a lot of organics, and 4)time. It occurs in volcanic regions all over the world! Important deposits are found around the Pacific rim: on the west coast of South America, in Central America, the Rocky Mountains, Alaska, Japan, the Philippine Archipelago, Indonesia, Papua New Guinea, and New Zealand. They are also prominent on many islands in the Pacific: Fiji, Vanuatu, New Hebrides, New Caledonia, Samoa, and Hawaii. In Africa, major occurrences of Andosols are found along the Rift Valley, in Kenya, Rwanda and Ethiopia as well as Madagascar. In Europe, Andosols occur in Italy, France, Germany, and Iceland. In total, there are some 110 million hectares of the earths surface that is covered with andosols. More than 1/2 of this is in the tropics. In a word, they're common. Here's a map of their distribution in the US.



Scott

 

[markyscott]

Actually, one more thing on akadama.

It's mined, sieved and kiln dried. It's not fired like many of the other soil components in common use. So it's softer and will break down over time. How rapidly is dependent on your climate and growing conditions. Here in Houston it's damp and humid. It rains alot and can get quite hot. But it rarely freezes. I water 2-3 times a day in the growing season and the "high-fired" akadama lasts at least 4-5 years without significantly breaking down.

Scott

 

[markyscott]

Let's talk about haydite. It's also known as LECA (lightweight expanded clay aggregate) or exclay (expanded clay). It's all the same stuff. Haydite and it's daughter products (Gravelite, Perlite, Rocklite) were made in the US, LECA was manufactured in Europe.

First thing you have to know is that haydite is a manufactured product. It was invented and panted by Stephen Hayde in the 1900's in Kansas City, Missouri. His product was a structural grade lightweight aggregate. The process uses a rotary kiln to flash heat clay, shale or slate at temperatures of over 2200 degrees F. In the process, water in the shale flashes to steam and the material expands producing air pockets in the grains. The heat also sinters the rock making it quite hard. It's essentially a ceramic. The end product is a strong and durable lightweight aggregate used in numerous types of construction throughout the world.



The first significant use of "Haydite" was in the construction of the hulls of several liberty ships in World War I. This application was very successful and was continued in the second World War. Hayde's first permanent production plant was built in Kansas City. Hayde patented the process and licensed the production to numerous other producers. Thus the name "Haydite" was born. Although the original patents have long since expired, the term "Haydite" is still used by several companies in marketing their expanded shale lightweight aggregate.



So what do you need to know? Haydite is:

1. A ceramic - it's chemically inert
2. Has some microporosity due to the manufacturing process
3. Is incredibly strong and hard - it won't break down over time
4. I pretty light weight - it won't add a lot of weight to your pot
5. Can be a bit variable in texture depending on the starting material - it can be manufactured from clay, slate or shale
6. Comes in a wide range of sizes
7. Is cheap and readily available.

Scott

 

[A Random User]

Scott, I have read a couple of articles as of lately regarding the properties of clay being organic, or inorganic...

From what I have come to understand from these is that for the most part clay if it was formed from inorganic material, it was thought to be inorganic... and vice versa for organic formed clays.

But, some were in fact beginning to question this thought... at least according to the article. They were finding that microscopic organisms were breaking down inorganics for the minerals that they posses as well. So, in essence what they believed was they were changing the status of the inorganic, to an organic through this breaking down, and the final product that was then left. I guess the thought being that if they were present, and died in the process, them and their waste, being now part of the overall makeup of a clay... then would changed the status of the clay seeing that they are living organisms.

Any thoughts seeing you are discussing clays, which i have always heard and believed and most would probably as well consider inorganic. I am just curious if a product that we use in Bonsai, that is in theory the by-product of an inorganic being broken down... could it in the process be changed to an organic state? Or do you feel they still would remain the same? Are some of these types of clays that we use, all considered inorganic, organic, or are there different types that are one of each? As well, could you possibly tell us when going through discussing the differing types of soils what state they fall into.

Again, not to get into a big heated debate over, don't care either way here... I dont know the answers and just trying to understand in a Scientific way, the material's we use and how they are made.
Thanks!

 

[markyscott]

Scott, I have read a couple of articles as of lately regarding the properties of clay being organic, or inorganic...

From what I have come to understand from these is that for the most part clay if it was formed from inorganic material, it was thought to be inorganic... and vice versa for organic formed clays.

But, some were in fact beginning to question this thought... at least according to the article. They were finding that microscopic organisms were breaking down inorganics for the minerals that they posses as well. So, in essence what they believed was they were changing the status of the inorganic, to an organic through this breaking down, and the final product that was then left. I guess the thought being that if they were present, and died in the process, them and their waste, being now part of the overall makeup of a clay... then would changed the status of the clay seeing that they are living organisms.

Any thoughts seeing you are discussing clays, which i have always heard and believed and most would probably as well consider inorganic. I am just curious if a product that we use in Bonsai, that is in theory the by-product of an inorganic being broken down... could it in the process be changed to an organic state? Or do you feel they still would remain the same? Are some of these types of clays that we use, all considered inorganic, organic, or are there different types that are one of each? As well, could you possibly tell us when going through discussing the differing types of soils what state they fall into.

Again, not to get into a big heated debate over, don't care either way here... I dont know the answers and just trying to understand in a Scientific way, the material's we use and how they are made.
Thanks!

Hi Sawgrass. Clay minerals are most definitely inorganic. All minerals are inorganic by definition. However, clay minerals are a component of soil which is most definitely rich in organics. And clay in the soil is a habitat for many micro-organisms.

For example, akadama, as I pointed out above, is most definitely a soil. It is intimately associated with organics - in fact the name refers to the dark humic layer that forms as the top layer (see the picture above). Micro-organisms help to fix the pH which controls how much aluminum is bound up in the inorganic clays and how much of it forms complexes with the organic compound humus.

Clay minerals have a large polarized surface area. So cations in the ground water are electrostatically bound to the clay surfaces. Plants exploit this to get the nutrients they need from the soil as do microorganisms.

In short, clay minerals are definitely inorganic, but the soil in which they are found is strongly influenced by organic processes and organic compounds of one sort or another are common and associated with the clays. The clays themselves are part of the habitat of organisms which live in the soil. Look at this living soil that Wireme posted.


This is one of his bonsai trees. The soil medium he used has all inorganic components, but the soil itself is exploding with life. Mycorrhizal fungus has invaded every pore. There are insects and roots everywhere as well as a complex biology of microorganisms.

Scott

 

[Anthony]

Scott,

just curious did wireme stay totally inorganic in all his applications ?

Offered to the class.

We noted trees growing well on just gravel and crushed red brick heaps.
[ our Caribbean Pine Forests are only pure silica based gravel / sand ]
Especially mimosa pudica [ nitrogen fixer ] on the crushed red brick.
Plus sightings of bird poop, fallen decayed matter and just dust from the atmosphere.

In other words the organics arrive no matter what.

Don't the guys who use inorganic mixes frequently use rape or soybean meal ?
Adding back in organic material.

As far as I remember clay soils are considered the most fertile soils, and the old way
to plant on them was to make a small hole and drop all the weeds / grasses cut in
the areas, the decay process than supplies every other factor. [ Rodale ]

We use that idea with all of our trees, just spoonfuls of aged compost during the wet
season [ though we used to use an osmocote type for the rainy season ]
The extra humidity made everything grow way to fast and thick.

As Paul of Australia taught us, you can grow on any stable medium [ for support ]
hence the test with marbles, 3 mm glass spheres, lecca, hand rolled 8 mm fired clay balls
pure 5 mm silica based gravel, pure 5 mm crushed red brick [ this one the plants didn't
like as much ]

We also applied that information to 1 inch deep pots with gravel and a very little aged compost
and ficus. We are able to take a tree from seedling to 3 inches in trunk, in one year if needed with
ficus.
Testing for J.b.pine to see how it responds, as well as the tamarind and a few others.

Great lecture thus far.
Thank you.
Good Day
Anthony

* And no, no sightings of organic clogging the drainage holes.

 

[Tieball]

@markyscott
Thanks for sharing this information. It is helpful.....and answers a lot of questions I didn't know I had. So....please keep answering the questions I don't know enough to ask.