Introductory soil physics

[markyscott]

Scott, I think that's some very complex stuff you're touching on in the last post. Most of the research that I've seen is devoted, of course, to standard container culture/mixes and if I recall, the results show that water with high alkalinity can cause a build up of compounds that raise soil pH. I would think you're more up to date on that kind of thing than I am. I have no idea how it would apply to our mostly inorganic "soil" mixes. However, I have seen reports that, for example, the pH of turface can vary widely from batch to batch. What I don't know is, how strong of an effect is that. For instance, rain can be pretty acidic on the pH scale, but since it is weakly buffered (hope I'm getting my chemistry right) its pH can be very quickly and easily altered. So using highly acidic rain for watering might not have much impact on the soil pH. Similarly, maybe turface (and lava) can have relatively high pH but those might be weak effects?

Not sure if I'm conveying my thoughts very well so I'm going to stop...feel free to correct anything I've gotten wrong.

Plus...to measure the pH of a solid like turface or lava, I believe you have to crush it and mix with distilled water. We don't really have that happening in our pots so not sure how relevant those values are?

Hmm...

Since scoria and pumice are essentially glass, and dont dissolve in water, I would think that any pH effects from the dust would get washed out pretty quickly.

Thanks Adair and coh for your thoughtful responses. I have a sneaking suspicion that by far the most important thing for us to consider when it comes to pH is what it is in the water we put into the pot. But I conjecture. Let me get back on track.

Scott

 

[markyscott]

A couple of additional follow up references on akadama for the sake of completeness and in an effort to collect the supporting material together as a resource. Here's some xrd and compositional analyses:



Ref: https://tsukuba.repo.nii.ac.jp/?act...tem_id=19212&item_no=1&page_id=13&block_id=83

Here's a reference demonstrating that allophane is the primary mineral phase:
http://onlinelibrary.wiley.com/doi/10.1111/j.1747-0765.2006.032_6.x/abstract

Here's a great reference on andosols - where they are found and the key controls on their occurrence. Really good overall reference on andosols.
http://www.isric.org/isric/webdocs/docs/ISM_SM2.pdf

Scott

 

[Anthony]

Hmm,

when an inorganic is unstable, or sometimes stable, either make your mind to literally test every batch or
find something more stable. No great logic there.

To add on a little history from the 1970's, in Japan due to supply, J.B.pines were grown in sand or the
sand / akadama mix.
Trouble is you have read a little more to see what sand is in Japanese rocks.

The blend of akadama / sand was an attempt to make loam. Seems to be around Tokyo [ memory here, please correct]

What was started by 1970, was a new set of ideas, which I have mentioned in an earlier post. Based more
on Science. Note- most of the earlier soil mixes were attempts at making Loam.

We return you now to your normal viewing.
Good Day
Anthony

 

[markyscott]

OK - back to it. Here's where we've got to so far:

1. We've introduced the underlying physical principle of capillary action (without any math - I'm very proud of myself).
2. We've talked about how capillary processes control the water saturation in the soil
3. We've talked about how saturation changes with height in a container as a function of soil properties
4. We've talked about what soil properties influence saturation
5. We've talked about what saturations and air-filled porosities are good for plant growth
6. We've talked about 4 types of inorganic soil components (we can touch on others if you like)

Here's where we still have to go to pull all this theory together with some data to provide some practical information

1. We need to talk about how to measure porosity, AFP, and water holding capacity (WHC)
2. We need to test some soil

Now with any test, we have to have a question in mind. So we will think about two questions

1. How does WHC and AFP change as a function of grain size?
2. How does WHC and AFP change as a function of grain type?

So that's where we'll go next, but I want to make sure we're all on the same page.

Scott

 

[0soyoung]

Now with any test, we have to have a question in mind. So we will think about two questions

1. How does WHC and AFP change as a function of grain size?
2. How does WHC and AFP change as a function of grain type?

So that's where we'll go next, but I want to make sure we're all on the same page.

Ah, the good stuff!
It is safe to presume this is why you did all the work sifting?

 

[Adair M]

I'm waiting for the part where he teaches us how to graft juniper onto plum trees!

 

[aml1014]

I'm waiting for the part where he teaches us how to graft juniper onto plum trees!

Or vice versa!

Aaron

 

[markyscott]

Ah, the good stuff!
It is safe to presume this is why you did all the work sifting?

I think you know where this is going. But we'll get all the numbers calculated and compiled in one place for folks to reference.

In terms of how to measure these properties, it's super easy - anyone can do it on their own. In fact - this is basically a 6th grade science experiment:

http://www.education.com/science-fair/article/testing-porosity-of-soils/

And you thought all that science crap you learned in grade school was worthless. Probably wishing you hadn't slept through that class now. Here's how you do it:

• You'll need at graduated cylinder or a plastic measuring cup (they used a glass measuring cup in the grade school version). You can buy graduated cylinders from Amazon for under 6 bucks. Drill a hole at the very bottom.

• Fill the cylinder up with soil. How much you put in there is important. Remember that the field capacity will go down as a function of the height of the soil. So if you're trying to find out the water saturation in your pot, you'll need to fill the cylinder up to the depth of soil your bonsai pot. If you plan on using a drainage layer, make sure you put one of those in the cylinder as well.
• Next thing you do is make a note of the volume of soil in the beaker.
• To do the experiment, start with a fixed amount of water. Holding your finger over the hole on the bottom, pour in water until the water level just reaches the top of the soil and see how much water you have left. The difference between the water volume you started with and that you finished with is the total porosity of the soil.
• Place a second measuring cup beneath the cylinder and remove your finger. Measure the amount of water that drains out. The volume of water that comes out is the air-filled porosity. You want this number to be 20% or so. higher is good, but you'll need to water more often. Below 10% and you have waterlogged conditions and the plant growth will suffer.
• The difference between the volume of water you poured in and the amount that comes out is the water holding capacity or field capacity. The more of this you have, the less you have to water, but there's a trade off between the AFP and the WHC.

See? This is how your experiments will go. Unfortunately there is no Shiner involved. But on the bright side, they're really easy to do and so you'll be done very quickly. Then you can get BACK to your Shiner without missing much football.

But the real power here is that you can check your own soil mix. You don't have to depend on me or anyone else to do it - you are EMPOWERED. You can do the exact same experiment by measuring weight too - you might be able to make your measurements more accurately if you have a good scale. Just do all the same steps, except measure the weight of the soil after each step. You can calculate the volumes using the density of water (1g/cc).

Scott

 

[markyscott]

I'm waiting for the part where he teaches us how to graft juniper onto plum trees!

Or vice versa!

Aaron

These are both very advanced techniques. I'm not sure that either of you are ready yet.

S

 

[aml1014]

These are both very advanced techniques. I'm not sure that either of you are ready yet.

S

Oh boy, I know I'm not!!! Lmfao

Aaron

 

[MindTone]

1. We've talked about 4 types of inorganic soil components (we can touch on others if you like)

Scott

May I request some info on Danish moler (diatomaceous earth), our European kittydama.
Love this thread by the way! Really interesting and wonderfully geeky what with all the science. Great work!

 

[markyscott]

May I request some info on Danish moler (diatomaceous earth), our European kittydama.
Love this thread by the way! Really interesting and wonderfully geeky what with all the science. Great work!

We can talk about diatomaceous earth. I'm not a big user because the variety we have here is pretty fine grained. But we can have a look. A lot of folks like it here.

Scott

 

[Anthony]

Hmm, an awareness of the water holding capacity of your individual components in the soil mix.

Yes, we did a similar test on the 5 mm crushed red brick.
[ if you look at Mark's particle size images earlier, the one with multiple sized particles, would
be what you want for concrete casting, nice and tight/dense.]

At this point I would ask how much an earthenware pot controls the perched water table, cools
the soil by evaporation and helps with the prevention of over watering.
That's a porous earthenware pot, one can today produce vitreous earthenware at under 900 deg.c
and lower. Saves money on the firing.
[ In the old days of no minimum wage ----- porous / winter / break ----- not a problem just get
the potter to make a new one ------------ also bury the pot in chopped straw or other to protect it.
Today -------- pot costs. So you look for vitreous, but lose the above named properties ---- interesting --
Then all these soil mix problems ------ hmm ]

It takes 3 to 5 years to learn to water correctly, and the degree of difficulty goes up for trees/shrubs
not native to your area.

Peat moss holds 15 times it's weight in water. We had to apply this information recently as two of
our fast growing trees, mastered the soil, and with the leaves being paper thin, responded by
turning them yellow and dropping them.

Now both plants are in larger pots, peat moss added in on the side. aided with mesh, as I mentioned before,
yellowing has stopped and they are good until 2 Jan.2017 when repotting begins.
Good Day
Anthony

 

[markyscott]

...At this point I would ask how much an earthenware pot controls the perched water table, cools the soil by evaporation and helps with the prevention of over watering...

When you water, the water saturation of the soil after gravity drainage is purely a function of the soil itself. The only characteristic of the container that matters is how tall it is.

Now, after you water, the saturation will go down due to evaporation and transpiration. So if you have waterlogged soil, those factors will control how long your soil will stay waterlogged after you've watered. Be aware that plants don't transpire well under waterlogged conditions that's why many have adapted by growing aerial roots. That's also why it's difficult to tell the difference in symptoms of a plant that's been overwatered or underwatered. So you'll primarily be relying on evaporation to reduce water saturation to the point where the tree can effectively transpire. Anything you can do to help that is good.

Scott

 

[Anthony]

Okay, here is use of the soil water holding properties / awareness.

Tree has mastered the soil and is drying out by 12.00, lunch time and leaves are falling [ image 1 ]

Tree is larger pot [ thanks Adam ] with 1/2 inch to 1 inch of peat moss all round the sides [ image 2 ]
and underneath.
Separated by a mesh, is the old soil from the new soil.
Yellowing has stopped and this week new shoots were trimmed of.

Idea is a leaning tree with a simple canopy.
Good Day
Anthony

 

[Anthony]

Another example same species but this in 3 mm glass spheres and aged compost.
Same problem - dried out.
Once again will have to add on peat moss for water absorbing / retaining abilities.

2nd image - the glass spheres and aged compost.

Thanks Paul
Good Day
Anthony

On going test project


3 mm glass spheres

 

[Adair M]

Okay, here is use of the soil water holding properties / awareness.

Tree has mastered the soil and is drying out by 12.00, lunch time and leaves are falling [ image 1 ]

Tree is larger pot [ thanks Adam ] with 1/2 inch to 1 inch of peat moss all round the sides [ image 2 ]
and underneath.
Separated by a mesh, is the old soil from the new soil.
Yellowing has stopped and this week new shoots were trimmed of.

Idea is a leaning tree with a simple canopy.
Good Day
Anthony

View attachment 119346



View attachment 119347

Anthony,

When you use Google, would you get pretty much the same search results as I would here in the US?

If so, try doing a Google search of "zelkova bonsai". And then, click on the images tab. And look at the images. When I do it, I see primarily broom style trees. Some are in pots shaped much like the ones you pictured in your post. Some are in pots much shallower and significantly wider than yours. In fact, they could almost be considered to be pots people use for planting forests.

So what?

Take another look at the trees in those shallower pots. From what I can see, the trees in those shallower, wider pots tend to be more highly ramified, with more small twigs, more leaves than the ones in the deeper, less wide pots.

Now, there may all kinds of reasons why this sample of images are like that, but it would seem surprising that those shallow pots could support all that foliage!

Except that Scott has told us that shallow and wide has the ability to hold more water than narrow and deep! (Assuming the same volume of soil.). And you can prove it to yourself using a simple kitchen sponge.

So, I think you ought to consider going to a wider, shallower pot. Rather than using the screen and peat moss. And aesthetically, the wide/shallow would look better, too!

 

[markyscott]

Anthony -

I'm desperately trying to avoid discussions that begin with "well I did this and this worked for me" or other such anecdotal posts that has always destroyed otherwise useful discussions of how this all works. So I'm not going to comment on your posts other than to say, what you need to know about water retention and aeration is in this thread. If you're unhappy with how your soil is performing with respect to these two things, there are aspects of your soil you can change to improve it. Specifically: 1) grain size, 2) grain shape, 3) sorting, 4) grain composition, and 5) the depth of your container. That's it. I don't advocate for nor will I comment on various soil shenanigans people do to try and trick the physics. It's not trickable and it's really simple if you boil it down to the fundamentals.

Scott

 

[markyscott]

...How does WHC and AFP change as a function of grain size?...

OK - I did this experiment with Turface. I did it because the coarse grained fraction of Turface is by far the most expensive soil I own and I worked harder for it than anything. A 50lb bag of Turface will yield less than a liter of soil in the 1/4"-3/8" size fraction. So I wanted to use it.

Here's the set up:

3 size fractions:


Scott

 

[markyscott]

I measured out 500ml of each fraction in a graduated cylinder:


I then measured out 1000ml of water:


Held my finger over the bottom hole on the cylinder and poured the water over the soil until the water level reached the soil surface. Here's the amount of water left in the measuring cup after having done so.


725ml. That means there's 275ml of pore space in the beaker. Now let the water drain into another beaker. The amount of water that comes out is the air-filled porosity. The difference between what you put in and what came out is the water holding capacity of the soil. The soil's water saturation is the percent of the soil porosity filled with water. So WHC/porosity. That's it.

Scott