Pumice and lava rock comparison

[coh]

The solution will be highly dependent on the grain size, the sorting, and the container height. As you decrease the grain size, the porosity will stay about the same, but the water filled porosity will increase and the air filled porosity will decrease. Decreasing the container height will have the same effect.

Scott

Sure. I did my best to sort to get similar sized particles (except for the turface, which is smaller). Did not evaluate what the difference might be relative to container size or shape, did not try to measure porosity (maybe next time)...just looking to see how much water equal volumes of particles could hold.

 

[fredman]

These questions are source of controversy and most often lead to many differences of opinion. There are a few here religious about soil components of which both items you mention. Me as we'll as Adair Brian and few others. Seek out one you trust and ask them by pm and get a solid answer free of all the distractions this group can bring.

Smoke. I and others value the comments of others here. When I PMd you about humic acid you told me to read up. When I did I only found mentions of it.
This discussions is what we need. That is the point about the forum.
If you have something to add please do so as people value any input. If not I will appreciate if you keep it to yourself rather than your snarly comments every now and again. That is not what I signed up to....

Freddie

 

[Giga]

I like them both, as I use them both, but soil is such a heated debate in the bonsai world, Much like politics I find that pumic does retain less then "lava" but I don't use these two by them self as I found a good mix that works for me. I use Pumice,"lava",turface,pine bark, and a splash of horticultural charcoal. I sift and wash each component and then ratio out each in a mix depending on the tree and it's development. I can get all these in bulk and cheaper then akadama, so it's what I use and it works well. I have gotten black lava which I think is the same thing as the red but I'm not sure

 

[BonsaiJack]

RE:

Hello Kennedy. Good questions. We have a 16 page soil report that will be released after the 27th. The report covers this exact topic, among others. This is my view on the subject...

Aeration is affected by particle size, not a particular aggregate. 1/4 inch material contains a good amount of breathing room. Turface sized material(1/8th inch and below) tends to have reduced breathing room and evap rates.

CEC(Cation Exchange), cannot be measured on 1/4 inch aggregates without pulverizing them. This makes the test ineffective due to increased surface area. We need to rely on water tests.

This graph will address your moisture retention question.

Hope this helps. Feedback is appreciated. This is a rough draft graph that is still being finalized.


BonsaiJack

How does lava and pumice compare as far as moisture retention, aeration, and CEC? I was thinking of only using one or the other along with akadama for next seasons repotting.

I'm in favor of lava rock just because it looks nicer mixed with akadama than pumice does, but everyone was going crazy about pumice last year after the Hagedorn article on Turface.

 

[markyscott]

Hello Kennedy. Good questions. We have a 16 page soil report that will be released after the 27th. The report covers this exact topic, among others. This is my view on the subject...

Aeration is affected by particle size, not a particular aggregate. 1/4 inch material contains a good amount of breathing room. Turface sized material(1/8th inch and below) tends to have reduced breathing room and evap rates.

CEC(Cation Exchange), cannot be measured on 1/4 inch aggregates without pulverizing them. This makes the test ineffective due to increased surface area. We need to rely on water tests.

This graph will address your moisture retention question.

Hope this helps. Feedback is appreciated. This is a rough draft graph that is still being finalized.


BonsaiJack

Seems interesting, and thanks for posting this. I agree with your point about particle size. It's far more important than grain composition in determining water saturation. But how can I determine total porosity and air-filled porosity from this chart?

Scott

 

[Vance Wood]

That which we call "lava rock" is "scoria" to geologists. Pumice and scoria are both volcanic rocks made from rapidly cooling erupted lava. The holes are formed when the lava quenches with trapped gas bubbles inside. Pumice and scoria are differentiated by density alone - pumice is less dense than water and scoria is more dense. They are both volcanic glass (no or very few minerals). Scoria tends to be more common with more mafic (higher iron and magnesium) volcanoes, but other than that and the density, they are quite similar.

In terms of water retention, I expect there is some variability. But the pumice and scoria I've tested have quite similar water retention and air filled porosity as long as the grain sizes are similar.

Scott

Is not Akadama a volcanic element much like Pumice?

 

[Paradox]

This year, I started using a 50/50 mixture of pumice and lava that I then add pine bark to depending on the species Im dealing with. I will be looking to add some horticultural charcoal to that mix this year if I can get a hold of some. I repotted a few trees into it this year and plan to repot some next year. It is too rearly to provide any results yet, but I dont anticipate any problems.

I just hope I can find more pumice this year. It seems the member that I got it from last year has disappeared.

 

[M. Frary]

Smoke. I and others value the comments of others here. When I PMd you about humic acid you told me to read up. When I did I only found mentions of it.
This discussions is what we need. That is the point about the forum.
If you have something to add please do so as people value any input. If not I will appreciate if you keep it to yourself rather than your snarly comments every now and again. That is not what I signed up to....

Freddie

In Al's defense there are pages of discussion on substrates here. Soil wars. Read the threads and see what I mean. Why beat a dead horse. Use what works for you in your area. Trees really don't care about any of it. They are above worrying about cation exchange and all. Ask one. He will have nothing to say.

 

[fredman]

Mike I did and I do. Actually speak several tree languages and understand some more dialects... Its not about soil at all. Its about discussions... "this lot" does not distract me and that is the point. Any input is valuable and any discussion is welcomed by me and others. Someone might bring in a new light bulb to the room. I and others don't believe in "do as I say". In the finish I can only decide for myself, if I have constructive discussions.....

 

[markyscott]

Is not Akadama a volcanic element much like Pumice?

Hi Vance. I'm glad you asked.

Akadama is a volcanic soil - it is comprised of partially to completely altered ash and pumice. It's parent material was from arc volcanics, probably andesitic in composition. 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 (http://www.tachikawa-heiwa.com/Introduction.html). The boundaries between these layers are called soil horizons. These kind of soils are called Andisols. Ando- is Japanese for "dark" and -sol means soil. It refers to the dark, humic-rich upper layer of the soil. This layer is part of the definition of an andisol - it must occur within the upper 15cm of the ground surface. 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 gone now and replaced by clay minerals.

The alteration is interesting - with a lot of water, the ash breaks down to form allophane and imogolite, clay minerals that commonly occur together in an andisol. In fact, their occurrence is nearly diagnostic - andisols 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 from the surface and form Al-humus complexes that can substitute for the allophane-imogolite clay association. 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 with subsidiary al-humus complexes whereas kanuma is dominated by Al-humus complexes with subsidiary clay minerals.

Scott

 

[markyscott]

Hi Vance. I'm glad you asked.

Akadama is a volcanic soil - it is comprised of partially to completely altered ash and pumice. It's parent material was from arc volcanics, probably andesitic in composition. 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 soils are called Andisols. Ando- is Japanese for "dark" and -sol means soil. It refers to the dark, humic-rich upper layer of the soil. This layer is part of the definition of an andisol - it must occur within the upper 15cm of the ground surface. 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 gone now and replaced by clay minerals.

The alteration is interesting - with a lot of water, the ash breaks down to form allophane and imogolite, clay minerals that commonly occur together in an andosol. In fact, their occurrence is nearly diagnostic - andisols 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 from the surface and form Al-humus complexes that can substitute for the allophane-imogolite clay association. 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 with subsidiary al-humus complexes whereas kanuma is dominated by Al-humus complexes with subsidiary clay minerals.

Scott

One additional thought while I'm on the subject. There is nothing special about the andisol in Japan used to make akadama (other than the fact it is the only place it is done). To replicate the conditions in Japan, you need 1)volcanoes, 2)a lot of rainfall, 3)a lot of organics, and 4)time. Andisols are widespread. About 50% of the andisols on the planet are in the tropics because of 2 and 3. But they can also occur in temperate areas where there is a lot of rainfall - Oregon, for instance, has abundant andisol. You won't find them among fresh tephra deposits though. You must go to places where the tephra has had time to break down to form these clay minerals. And you must look in places where abundant plant material has grown to form the thick layer of capping humus. If you Google andisol + map + USA and you'll be able to find a map of their occurrence ...

Scott

 

[markyscott]

Map of the distribution of allophanic andisols in Japan (from Takahashi, Tadashi, and Sadao Shoji. "Distribution and classification of volcanic ash soils." GLOBAL ENVIRONMENTAL RESEARCH-ENGLISH EDITION- 6.2 (2002): 83-98.APA) and the location of Kanuma, Tochigi Prefecture, Japan (where akadama is mined).

Scott

 

[Mike Corazzi]

Found this old post from a Google search. Interesting as at this time, I am interested in trying to get my Scots pine a bit lighter in weight, considering the large pot it's in.

My first inclination is to switch FROM lava to pumice with some (more expensive and SPECIAL)...extra hard aka. And a BIT of some kinda organic as we can't get pine bark here.

The guy who gives our regular weekly classes thinks the pumice would do very well and better than lava for root ramification.

But this thread seems to say that lava holds MORE water and all this time I've been reading here that pumice is what retains water.

All I want to do is get the pot lighter in weight so an old coot can LIFT it.

I suppose I could do SOME lava with MORE pumice and the rest of that stuff.





......Weakling out.......

 

[Arcto]

Pumice (3/8" grain size)
Porosity = 31%
Air-filled porosity = 26%
Water-filled porosity = 5%

Scoria (3/8" grain size)
Porosity = 40%
Air-filled porosity = 20%
Water-filled porosity = 20%

So, this pumice has lower porosity than scoria, but higher air filled porosity and lower water retention.

Scott

Thank you Scott! This is the kind of soil information I enjoy reading as opposed to heated debates that get personal.

 

[sdavis]

Pumice deposits in Oregon vary quite a bit as far as density, CEC, and water retention.

 

[GrimLore]

All I want to do is get the pot lighter in weight so an old coot can LIFT it.

I rinse and soak Horticultural Perlite then add large amount. Hell of a lot lighter and the plants don't seem to give a damn.

Grimmy

 

[my nellie]

Perlite holds a lot more water than pumice and lava.

 

[EPM]

Perlite holds a lot more water than pumice and lava.

Based on my own tests I've come to the same conclusion. Perlite holds more water and per unit volume has more open space for holding air/oxygen than lava or pumice. In other words, Perlite displaces less water per unit volume but also retains more water than a similar volume of pumice or lava. This makes sense because of how light it is. I don't know that it makes it a superior substrate, just that it's better in those respects. This is just based upon what is readily available in my area and obviously others may have access to materials with different characteristics as @sdavis mentioned above.

 

[markyscott]

Perlite is just man-made pumice. It's exactly the same chemical composition as pumice, but different texture due to the way it's made. You can read about the details here.