Introductory soil physics

[Agriff]

Akadama is too water retentive for my conifers, in my climate, with my watering habit. I water too often, my temperatures are too low to cause enough evaporation and my conifers don't like soils that stay wet for too long. It would be better for me to use some other component like perlite, pumice, lava rock, these however balance on the edge of being not water retentive enough, so I add some pine bark to end up somewhere in the middle.

This is the first time I've heard anyone say that akadama is too water retentive! But reading the rest of the thread that makes total sense. I'm so intrigued by your mix because I am also a heavy waterer and live in a much colder climate- Minnesota, which is roughly 45 degrees latitude. Now, even Maastrict is much further north, but I'm still curious what you use. How much pine bark are we talking?

 

[Vance Wood]

I doubt we will ever resolve a soil mix for the North Central States of America. I have been grown bonsai for over sixty years and I have never used Akadama, or have known anyone who does/did use it. I recently ran into a soil issue but I came to find out it was not because of the soil so much as the screen I was using in a couple of instances was too fine and the sand was just the tight caliber that coused it to plug up the screens.

 

[River's Edge]

This is the first time I've heard anyone say that akadama is too water retentive! But reading the rest of the thread that makes total sense. I'm so intrigued by your mix because I am also a heavy waterer and live in a much colder climate- Minnesota, which is roughly 45 degrees latitude. Now, even Maastrict is much further north, but I'm still curious what you use. How much pine bark are we talking?

A simple solution I found is to adjust the percentage of akadama in relation to the other components. I live in a rainforest type environment. With 20 % akadama I can water as much as I want with pines and juniper that like drier conditions. With other species I increase the Akadama to 25% or 30% to ensure a bit more moisture retention. My components are all served to the same size and free draining with adequate air space between particles.
I am not suggesting one has to use Akadama, just that one does not have to stick to one set of proportions when mixing components.
I also add granite grit, little to no moisture retention but excellent stability and also inorganic to retain free draining condition and add some weight to the mix. Particularly important if developing trees in windy conditions. Lighter substrates can be problematic with large sacrifice branches and apical sacrifice leaders.

 

[Wires_Guy_wires]

This is the first time I've heard anyone say that akadama is too water retentive! But reading the rest of the thread that makes total sense. I'm so intrigued by your mix because I am also a heavy waterer and live in a much colder climate- Minnesota, which is roughly 45 degrees latitude. Now, even Maastrict is much further north, but I'm still curious what you use. How much pine bark are we talking?

I'm 50 miles north of Maastricht even! I use pine bark flakes 5-10% by volume. You can see it's in there but the main components are still a blend of 1:1:1 lava rock, pumice and granite that I use straight from the bag.
Akadama is problematic in the spring, fall and winter for me. For deciduous I use more bark, but it's trial and error process.
I can highly recommend getting a couple cheap trees from major plant groups (conifers, broadleafs) and try out some blends before you put your more important trees in a certain soil.
Climate is one factor, your watering habits and pot size are another important factor.

 

[Agriff]

I'm 50 miles north of Maastricht even! I use pine bark flakes 5-10% by volume. You can see it's in there but the main components are still a blend of 1:1:1 lava rock, pumice and granite that I use straight from the bag.
Akadama is problematic in the spring, fall and winter for me. For deciduous I use more bark, but it's trial and error process.
I can highly recommend getting a couple cheap trees from major plant groups (conifers, broadleafs) and try out some blends before you put your more important trees in a certain soil.
Climate is one factor, your watering habits and pot size are another important factor.

Thank you so much for your reply! Yeah, I'm trying out some mixes on some invasive species that I dug up from my lawn, so literally zero risk for the time being, aside from the time it takes to water. I appreciate your approach

 

[Orion_metalhead]

Has anyone tried using hardwood wood pellets in small amounts in their bonsai soil as a moisture retention ingredient? Just curious. I may try this upcoming spring out of curiosity.

 

[markyscott]

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.
View attachment 119104

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

A combination of good soil and careful watering make for a good microenvironment for organisms. You can see how mycorrhizal fungi will thoroughly colonize the pore space right to the soil surface. Just pushing aside the top layer of grains should reveal a complex network of life.

It can even push the soil surface up into small mounds.

A healthy system will colonize every pore, to the point where it occludes a significant fraction of the pore space, making it difficult to water. This pine is one such case.

 

[markyscott]

A combination of good soil and careful watering make for a good microenvironment for organisms. You can see how colonization by mycorrhizal fungi will thoroughly colonize the pore space right to the soil surface. Just pushing aside the top layer of grains should reveal a complex network of life. View attachment 417234View attachment 417233

It can even push the soil surface up into small mounds. View attachment 417235

A healthy system will colonize every pore, to the point where it occludes a significant fraction of the pore space, making it difficult to water. This pine is one such case. View attachment 417240View attachment 417241

These were all taken on JBP. If you’re not getting this kind of performance with what you’re using, you should consider making modifications to your mix.

scott

 

[markyscott]

The grain size that I use on nearly all my trees is smaller than my largest sieve (0.28” or 7mm) and larger than my medium sieve (0.2” or 5mm).

 

[Huggz13]

As an aside and not to hijack a thread...

When I was in college I worked in the microbial ecology lab.

I worked with a post-doc who’s PhD was in soil science.

We used to call him Doctor Dirt.
He got so pissed off and would yell, “IT’S ******* SOIL, NOT DIRT!”

 

[markyscott]

More examples of living soil.

 

[Ugo]

A combination of good soil and careful watering make for a good microenvironment for organisms. You can see how mycorrhizal fungi will thoroughly colonize the pore space right to the soil surface. Just pushing aside the top layer of grains should reveal a complex network of life. View attachment 417234View attachment 417233

It can even push the soil surface up into small mounds. View attachment 417235

A healthy system will colonize every pore, to the point where it occludes a significant fraction of the pore space, making it difficult to water. This pine is one such case. View attachment 417240View attachment 417241

Hi!

Thanks for showing this example.
I have the same situation here, the top portion of the pot is is filled with mycorrhizal fungi making it difficult to water.
Do you rework the top layer or leave it as it is?
My tree was just repotted in March 22' and the pot is already filled with fungi.

My plan is to keep the tree for as long as possible before repotting. Can I ask if you sometimes rework the top so water can enter more easily?

Here's the tree too layer





Thanks
Ugo

 

[markyscott]

Hi!

Thanks for showing this example.
I have the same situation here, the top portion of the pot is is filled with mycorrhizal fungi making it difficult to water.
Do you rework the top layer or leave it as it is?
My tree was just repotted in March 22' and the pot is already filled with fungi.

My plan is to keep the tree for as long as possible before repotting. Can I ask if you sometimes rework the top so water can enter more easily?

Here's the tree too layer

View attachment 476434
View attachment 476435
View attachment 476436

Thanks
Ugo

Hi Ugo. Healthy looking soil! Don’t change a thing! If I don’t repot I always do the soji (clean the top soil). I use bent nose tweezers and, scraping radially away from the trunk, I remove the top 1/2” or so off the soil surface. I remove or adjust any small crossing or problematic roots and put on fresh soil. Then I re-moss. You’ll find that the water will penetrate much better.


S

 

[Ugo]

Hi Ugo. Healthy looking soil! Don’t change a thing! If I don’t repot I always do the soji (clean the top soil). I use bent nose tweezers and, scraping radially away from the trunk, I remove the top 1/2” or so off the soil surface. I remove or adjust any small crossing or problematic roots and put on fresh soil. Then I re-moss. You’ll find that the water will penetrate much better.


S

Thank you sir!
Let say that this tree doesnt seems to complain at all!
I will do some major styling work on this tree this year, I found it in really poor condition but its now a strong tree.
I repotted the tree in March 22 and started to see a difference with water have more difficulty to enter the soil around August.
The only thing I started doing when I saw this was titlting the pot after proper watering so the water that entered the soil could drain "throught" the core of the root mass and attain the core under the trunk.

I will for sure use the soji technique you suggested thank you.
I also found on the forum a detailed post you've made in the past explaining the technique, thank you for that.
Sounds stupid but I dont have a pair of bent nose tweezers.....
I really have all kind of tweezers, regular with spatula, a sturdy pair to remove pine needles, one made to remove flower buds on azalea and a pair of masakuni tweezers with blades just to cut buds... never find the use of the bent nose
Ok Ill have to get a pair!!
Knowing this work will be done around buds swell I will have to use something else...

Quick question about top dressing.
In the situation I found the mychrorizea was "acting" as a very good protective layer, as you mentioned the first 1/8 inch of soil can look bone dry but the mycorrhizal fungi layer right under keep the soil mass well protected with a higher level of moisture underneath.
If I use top dressing and the mycorrhizal layer form back in a couple months right under the new layer of soil do you see a possible issue with excessive moisture retention using top dressing with the very possible reformation of a mycorrhiza layer?
Just to give more general info on the tree.
The tree is a dwarf alberta spruce that's usually in full sun all day for almost 12hrs except on very hot part of summer where its moved and gets partial/full shade from 11-2pm and back in full sun until night time. One thing that might be a detail that could have some importance as Im trying to understand how to repeat this process... the tree is in a mica pot.
Mica pot are brown and can become really hot if left out in full sun without a cooling period in the afternoon.

As a side note the fungi also affect the drainage holes that I had to clean two times now to make sure the pot has proper water drainage.

Thank you again for the informations
Ugo

 

[Trasselkalle]

Living in a colder climate, I have issues with my sieved medium sized Akadama breaking down too fast. Potentially it could also be related to the quality of the Akadama, but I know many others around where I live that struggle with similar problems.

I have no problems getting hold of good Pumice and Scoria and have been testing extensively with various mixes and proportions that include organic materials (pine bark, peat of different kinds, etc) instead of Akadama to get the water retention up without getting issues with waterlogging especially during longer rainy periods. Sadly I haven't arrived at anything that works as well over the whole year as Akadama, but I want to get away from the yearly replanting (or accepting a less-than-ideal 2nd year).

You mentioned Seramis @markyscott which is available to me here in Europe. Are there any other practical aspects than what you share in #137 that are worth considering before starting to experiment with Seramis over Akadama given how similar the two are in your tests? How is the weight and does it break down in a similar way to Akadama or is it more stable?

Respecting the intent of the thread, I'm not looking for advice beyond what to keep in mind, as I rather enjoy the systematic testing process and need to figure out what works over the whole year here. I've just never worked with Seramis before.

 

[markyscott]

Living in a colder climate, I have issues with my sieved medium sized Akadama breaking down too fast. Potentially it could also be related to the quality of the Akadama, but I know many others around where I live that struggle with similar problems.

I have no problems getting hold of good Pumice and Scoria and have been testing extensively with various mixes and proportions that include organic materials (pine bark, peat of different kinds, etc) instead of Akadama to get the water retention up without getting issues with waterlogging especially during longer rainy periods. Sadly I haven't arrived at anything that works as well over the whole year as Akadama, but I want to get away from the yearly replanting (or accepting a less-than-ideal 2nd year).

You mentioned Seramis @markyscott which is available to me here in Europe. Are there any other practical aspects than what you share in #137 that are worth considering before starting to experiment with Seramis over Akadama given how similar the two are in your tests? How is the weight and does it break down in a similar way to Akadama or is it more stable?

Respecting the intent of the thread, I'm not looking for advice beyond what to keep in mind, as I rather enjoy the systematic testing process and need to figure out what works over the whole year here. I've just never worked with Seramis before.

I liked seramis and am sorry it is no longer available in the US. If it was, I would still be using it as a component of my mixture. I don’t consider it a substitute for akadama, but it is a good, stable product that works well with pumice and scoria. I liked that it was clean right out of the bag - no dust and no waste. It was almost 100% the right size and there was hardly any waste at all when I sieved. I give it two !!

Scott

 

[Trasselkalle]

I liked seramis and am sorry it is no longer available in the US. If it was, I would still be using it as a component of my mixture. I don’t consider it a substitute for akadama, but it is a good, stable product that works well with pumice and scoria. I liked that it was clean right out of the bag - no dust and no waste. It was almost 100% the right size and there was hardly any waste at all when I sieved. I give it two !!

Scott

Thank you, Scott - that sounds very promising!

I can add that a similar volume bag of akadama and seramis cost about the same for me. However, as your pdf reference sheet also illustrates, the great particle size and minimal waste makes seramis extra attractive even if it isn't a perfect replacement of akadama. Now who do I ask about getting an early spring so I can get going with my tests?

 

[Maiden69]

Scott, question. I was using mulch to fill my above ground beds in the previous home with great results, but when I had to pull the trees out to move I realize that the escaped roots actually grew into the mulch making it very hard to pull. I since have the idea to freight some pumice in, probably 1-2 cu Y to fill all beds, but at the price + freight I think I will be well over $1k. I am stopping by the local Napa to take a look at the size of their 8822, and see if it would be a cheaper option. I also researched a little on expanded shale, but couldn't find a supplier with smaller particles.

What other substrate/stone would you consider if you were doing the same thing? I'm not looking for a material to add into the pot, but a loose substrate that the roots won't grow into, will help retain moisture on the grow bags, and allow the roots to grow between the particles (not something that would compact hard like decomposed granite).

I still have around 5-7 months as they are supposed to break ground in the next 2 weeks with a build time between 4-6 months. I'm even considering taking a road trip with a trailer to Arizona, I think Acme Sands is the closest place to us that sells in bulk. That would be around half the price including a sleep over night to wait for them to open.

 

[Orion_metalhead]

What about pea gravel or something of that type? Easy to get in bulk and cheap. Holds moisture but roots wont grow intonthe substrate.

 

[Maiden69]

What about pea gravel or something of that type?

Most of the pea gravel I find in my area is the smooth one, that one don't hold moisture. I think it would work great as a ground cover, but not for a above ground bed.