Introductory soil physics

[Gustavo Martins]

Scott,

Is there a simple way to figure out the AFP, WHC and the CEC of a blend of components if you know the values for each of the components and their granulation (ie x<size<y) If there isn't a simple way to figure it out precisely is there a rough approximation given certain constraints?

Thank You
Jacob L'Etoile

I guess you can multiply the value of each component by its relative proportion in the mixture. However, this will be a very rough estimate. If you remember what Scott has shown, when you mix different grain sizes you increase AFP. So, when you mix different components, in addition to the above you are also creating a more uneven mixture of grain sizes. It's going to be hard to estimate how much, just figuring out each components' values.

My two cents

 

[markyscott]

Just went through. Great read.

I now understand that we should aim for a AFP of +20%. However, water is still necessary to retain moisture in between waterings. So my question is, is there also a number of WHC that we should aim for?

It would be very important to test how this varies over 24h. My understanding is that AFP will go up, whereas WHC will go down due to evapotranspiration and evaporation. So I suppose it will very much depend on local conditions (sunny, overcast), pot type (material, holes), plant water necessity. Still, being able to roughly measure how this varies over one day, should allow us to define target initial conditions right? It should also be reasonably easy to measure if we use mass over volume and have different test tubes that we take each at different times of the day, say every 3 h after watering, to measure the mass.

Hi Gustavo -

You've hit on a very important point. And this is one that makes soil choice very personal. You're right that there is a trade-off between AFP and WHC. When one goes up, the other goes down. And you're right that high AFP is quite desireable. 15-20% should really be the minimum for your substrate. Higher is better - I try to keep mine above 25% or so. But the higher it goes, the more frequently you have to water. So it's really on you to decide? How much care can you give your trees? Do you have time to water several times a day? Can you put in a watering system? Are you willing to get someone to care for your trees every day when you're out of town? If the answer is yes to those things, make the AFP as high as possible. Otherwise, you may have to build a more water retentive soil and sacrifice some AFP.

The time it takes for soil to dry depends on a lot of factors. The two main processes are evaporation and transpiration. How quickly this happens will depend on the season, the amount of foliage on the tree, the temperature, the humidity, the surface area of your pot - many factors. And it will change all the time. Somewhere in this thread someone pointed us to a youtube video in which someone did the soil-drying experiment. It was in German.

Hope that helps.

Scott

 

[markyscott]

...looking for what calidama is I've found some interesting blog pages.
http://www.bonsaijack.com/bonsaiblock_lava_pumice_turface_bonsai_soild_tests.html

Calidama is what Mr. Glen Van Winkle sells. It's crushed California hardpan. It doesn't break down.

Not at all like akadama. Mr. Van Winkle sells it as an alternative to akadama, which isn't a good comparison, in my opinion.

It's more like scoria (lava), but a lot heavier.

I have zero experience with Calidama. I've never even seen any of it in person. But it looks as though it might be just caliche, broken down and kibbled into various size fractions. Very different than akadama, but I think folks have used it successfully as a soil component. As long as it's the proper size fraction, it should be OK.

Scott

 

[markyscott]

Scott,

Is there a simple way to figure out the AFP, WHC and the CEC of a blend of components if you know the values for each of the components and their granulation (ie x<size<y) If there isn't a simple way to figure it out precisely is there a rough approximation given certain constraints?

Thank You
Jacob L'Etoile

CEC should just be the volume-weighted average of the CEC of the different components you're using for your soil. AFP and WHC are probably not quite that easy as the values are so sensitive to soil texture. I just measure the soil I want to use directly.

Scott

 

[markyscott]

Just to add to the data:

I've been playing with scoria (the red type) which I collected locally (lot's of it and pumice for free over here). I sieved the scoria and used a grain size between 2 and 4 mm (those were the sieves I borrowed from the lab).

However, instead of using lab glass I used a real oval pot (16 x 12 x 6 cm) I had around. Same procedure as described by Scott.

These are the values I got.
Soil volume: 400 ml
Pored water volume: 350 ml
Gravity water: 75 ml
Phi: ~88%
AFP: ~19%
WHC: ~69%

I have left the pot with the scoria outside. Basically, I want to get a feeling of moist it remains over the next 48 h without watering as I have no idea since I haven't used it yet. But the values above sound good no?

Glad you're doing the measurement Gustavo. Can you tell me what grain size that you've sieved to? The AFP seems a bit low. Are you using a fine grain size?

Scott

 

[Gustavo Martins]

Glad you're doing the measurement Gustavo. Can you tell me what grain size that you've sieved to? The AFP seems a bit low. Are you using a fine grain size?

Scott

Yes it was fine grained scoria between 2 and 4 mm.

I know this is a bit fine compared to the standard but these were the sieves with the largest mesh sizes of the set I had availabe at the lab. (I work with macrofauna and we tend to use much finer mesh-sized sieves, 500 micra). Got to buy (make) a larger one for myself.

 

[markyscott]

Yes it was fine grained scoria between 2 and 4 mm.

I know this is a bit fine compared to the standard but these were the sieves with the largest mesh sizes of the set I had availabe at the lab. (I work with macrofauna and we tend to use much finer mesh-sized sieves, 500 micra). Got to buy (make) a larger one for myself.

Hi Gustavo. That is quite fine grained which is why your AFP is low. I usually discard anything less than 1/8" or 3mm. Most of my soils is 1/4"-3/8" or 6-10mm. Is the coarse fraction a problem? Perhaps you can just keep the stuff that doesn't pass through your 4mm sieve.

Scott

 

[Gustavo Martins]

No it's not a problem at all, I can easily use coarser fractions, although I like the aesthetics of the fine grained soil. I can retry again with an unsieved soil and see what comes up. I will do it after calculating the time for this batch to dry (I only have one pot )

 

[markyscott]

No it's not a problem at all, I can easily use coarser fractions, although I like the aesthetics of the fine grained soil. I can retry again with an unsieved soil and see what comes up. I will do it after calculating the time for this batch to dry (I only have one pot )

Use the fine grained stuff as a top dressing. It will help reduce evaporation losses as well.

Scott

 

[wireme]

Use the fine grained stuff as a top dressing. It will help reduce evaporation losses as well.

Scott

Hi Scott, what would you say would happen when a finer grain is used at the bottom of the pot?

It's this article that has me wondering what good it could do.

http://minnesotabonsaisociety.org/i...per-ryan-neil&catid=7:miscellaneous&Itemid=14

A screenshot of the pertinent portion below.



Here's another screenshot from the article, not related to my question but something different than what I usually see.

 

[markyscott]

Hi Scott, what would you say would happen when a finer grain is used at the bottom of the pot?

It's this article that has me wondering what good it could do.

http://minnesotabonsaisociety.org/i...per-ryan-neil&catid=7:miscellaneous&Itemid=14

A screenshot of the pertinent portion below. View attachment 125289



Here's another screenshot from the article, not related to my question but something different than what I usually see.View attachment 125290

Interesting article. Thanks for sharing it. All else being equal, a fine grain soil at the bottom of the pot will increase the moisture content there - I'm not sure why that was important to him in this case.

The second point I think has to do with collected yamadori juniper. These are generally old trees and they don't spring back from root work the way young ones do. It's good to proceed carefully when pruning roots and removing old field soil. I've a couple of old ones and we generally take quite a bit of time to work back the old roots and work out the old soil.

Scott

 

[wireme]

Interesting article. Thanks for sharing it. All else being equal, a fine grain soil at the bottom of the pot will increase the moisture content there - I'm not sure why that was important to him in this case.

The second point I think has to do with collected yamadori juniper. These are generally old trees and they don't spring back from root work the way young ones do. It's good to proceed carefully when pruning roots and removing old field soil. I've a couple of old ones and we generally take quite a bit of time to work back the old roots and work out the old soil.

Scott

Thanks, perhaps a version of HBR, it sounds like this was the first repot after collection, maybe it will be removed next time or two around. I have seen a couple mentions of Japanese yamadori that still have original soil at the core despite many years of training and repotting. Everything else I come across says it's gotta go at some point.

 

[Brian Van Fleet]

Hey @markyscott :

https://www.facebook.com/video.php?v=10154263933902326

 

[markyscott]

Hey @markyscott :

https://www.facebook.com/video.php?v=10154263933902326

I thought everyone had that nightmare.

Scott

 

[Adair M]

I thought everyone had that nightmare.

Scott

I feel sorry for Marky!

 

[markyscott]

I feel sorry for Marky!

She's a geologist too! We both wake up to the same nightmare!!

Scott

 

[Adair M]

It must be difficult to get thru the day...

My daughter took a geology class this summer, traveling all around the country studying the local rocks.

We have a large piece of mica I found out in the pasture sitting on a table in the great room. My daughter walks by, picks it up and says it's a great piece of some unpronounceable mineral. So, I said I thought it was mica. She says, "Oh it is, but mica is composed of unpronounceable mineral one and even more unpronounceable mineral two!" She then points to mineral one and then mineral two.

And, I go: "Wow"! That was totally worth spending about $8,000 for tuition for you to learn!

Lol!!!

 

[markyscott]

It must be difficult to get thru the day...

My daughter took a geology class this summer, traveling all around the country studying the local rocks.

We have a large piece of mica I found out in the pasture sitting on a table in the great room. My daughter walks by, picks it up and says it's a great piece of some unpronounceable mineral. So, I said I thought it was mica. She says, "Oh it is, but mica is composed of unpronounceable mineral one and even more unpronounceable mineral two!" She then points to mineral one and then mineral two.

And, I go: "Wow"! That was totally worth spending about $8,000 for tuition for you to learn!

Lol!!!

Well. As long as she can pronounce them it was all worth it. And I can promise that there are much worse ways to spend your education dollars than on a geology degree. Because knowing the names of rocks is empowering. It can tell you the geologic history of an AREA!!!

S

 

[Adair M]

She's a music major. Double major in Horn Performance and Music Theory.

She took the Geology class to satisfy a Science, PE, writing, and something else, too.

She had a great time, and can identify lots of rocks!

(She can identify almost any classical piece of music, too!)

 

[markyscott]

I thought I'd add a bit more nuance to the discussion we had earlier in this thread concerning the relationship between grain size and porosity. When you read a geology or petrophysics textbook, they'll all tell you that porosity is not a function of grain size. And this is exactly correct. But as it is with everything, the devil is in the details. So, grab a shiner and let's dive in.

Scott