Thank you for response, so the shallower pot with the same L x W the bigger portion of root mass can be present in the same height of water column, waterlogged, that's the issue.
Introductory soil physics
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markyscott
Imperial Masterpiece
wireme
Masterpiece
I guess I didn't express myself well. I was talking about the pores that do fill with water not the closed pores. Your tests with the graduated cylinders start with the soil fully submerged, has to be that way to get all the results. When we water we may not get to full field capacity in the same way as we would by submerging the substrate. I haven't tested it but I think that's what was happening to me with pumice initially and I had to adjust my watering habits a bit to account for that. Granite with no pores to fill probably reaches full field capacity just by getting thoroughly wet. Pumice might have to have water run through it for longer or repeatedly, some of the organics that can be hydrophobic when dry may need even longer exposure to water.
markyscott
Imperial Masterpiece
Thanks for the clarification wireme, I misunderstood your question. And re-reading your original post your meaning is clear. I'm not exactly sure what the answer is though. But your inference about the experiments is correct. I measure the amount of water required to completely fill the available pore space to measure the porosity. Then I measure the amount of gravity drainage to determine the AFP and WHC.
Scott
coh
Imperial Masterpiece
Scott, I wanted to return to the idea of drainage layer and their impact on "perched" water, total water holding capacity, etc.
I was browsing through a back issue of the ABS journal (Vol 45 #3, 2011) and there was an article by @Owen Reich about "mizu goke." One line caught my attention (relevant section underlined):
"Kouka-en uses blended Aoki akadama mixes for everything (a separate deciduous and evergreen mix) with a larger size of high fired akadama as a base to decrease the zone of saturation..."
This seems to be at odds with the discussion from earlier in the thread? Maybe Owen can comment since he wrote it. But I believe the earlier discussion indicated that the use of a base layer with distinctly larger particles would create an elevated later of saturation above it which seems contradictory to the above statement. Maybe I'm misinterpreting something...
I was also thinking that maybe your method of using the graduated cylinders could be used to examine whether use of a drainage layer significantly changes the amount of water held in the mix? Just use a base layer of larger particles under a layer of smaller, and compare the results to an equal depth of uniform (smaller) particles...
Interesting stuff, this is something I'll be delving into in more detail this winter but wanted to put it down while I was thinking about it...
Chris
I was browsing through a back issue of the ABS journal (Vol 45 #3, 2011) and there was an article by @Owen Reich about "mizu goke." One line caught my attention (relevant section underlined):
"Kouka-en uses blended Aoki akadama mixes for everything (a separate deciduous and evergreen mix) with a larger size of high fired akadama as a base to decrease the zone of saturation..."
This seems to be at odds with the discussion from earlier in the thread? Maybe Owen can comment since he wrote it. But I believe the earlier discussion indicated that the use of a base layer with distinctly larger particles would create an elevated later of saturation above it which seems contradictory to the above statement. Maybe I'm misinterpreting something...
I was also thinking that maybe your method of using the graduated cylinders could be used to examine whether use of a drainage layer significantly changes the amount of water held in the mix? Just use a base layer of larger particles under a layer of smaller, and compare the results to an equal depth of uniform (smaller) particles...
Interesting stuff, this is something I'll be delving into in more detail this winter but wanted to put it down while I was thinking about it...
Chris
markyscott
Imperial Masterpiece
Hi Chris - it is seemingly at odds based on the excerpt you quoted, but I'd like to read the whole article so I understand the context. But the physics is clear - if you add a drainage layer it will effectively shrink the depth of the soil, increasing the overlying water saturations. Similar to the way saturation increased with decreasing soil height in the experiments I posted previously. It will not be exactly the same, for a couple of reasons:
- The height of the saturated zone is dependent on the difference in pore size above and below the drainage layer. If there is a really big difference, it will approach what we see in the experiments. But as the average pore size in the drainage layer approaches that of the soil medium the impact of the drainage layer goes away.
- There is also the issue of microporosity. Using a medium with or without (effective) microporosity will likely have some control on the impact the drainage layer has on the water saturation in the soil you are using.
Scott
coh
Imperial Masterpiece
Scott, the part I quoted is really the only relevant part. It was almost like a throwaway line in the article, which was mainly about the use of chopped sphagnum ("mizu goke") on top of the soil...to help keep the top layer moist and help determine when watering is needed.
Owen is going to be at our club meeting tonight, so if I get a chance I'll ask him about this (or at least ask him to check this thread). Generally there isn't enough time at club meetings to get into this kind of off-topic stuff in any detail, though.
Owen is going to be at our club meeting tonight, so if I get a chance I'll ask him about this (or at least ask him to check this thread). Generally there isn't enough time at club meetings to get into this kind of off-topic stuff in any detail, though.
Owen Reich
Shohin
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The zone of saturation will be affected by use of a drainage layer if the particle size difference is sufficient; which Scott stated above. So, height of zone of saturation would decrease.
See you at the meeting this evening.
See you at the meeting this evening.
markyscott
Imperial Masterpiece
markyscott
Imperial Masterpiece
I posted the first resource developed from our discussion. Please go in and have a look. I'd love to hear what you think.
http://www.bonsainut.com/resources/inorganic-soil-reference-sheet.28/
In it, I expand on and add to the discussion we had in the thread.
Scott
http://www.bonsainut.com/resources/inorganic-soil-reference-sheet.28/
In it, I expand on and add to the discussion we had in the thread.
Scott
hemmy
Omono
@markyscott, Thanks for the great resource!
Is there anything important to say about buffer capacities of the various substrates? (Especially for those of us with hard water)
Buffer Capacity as "reserve acidity is the concentration of hydrogen ions attached to the negatively charged clay particles and organic matter. This is measured as buffer pH. Buffer pH relates to buffer capacity of the soil: ability to resist changes in pH." - http://www.isafarmnet.com/ResearchPublications/06Nconf/E1.pdf
It would appear that akadama has some buffering capacity based on the presence of clay minerals (allophane complexes) and humus which you have previously highlighted. Although my SWAG (scientific wild-ass guess), is that it would be lower than peat and probably lower than pine bark. However is this buffer capacity and the expected higher buffer capacity of Kanuma one of the reasons it is recommended for azaleas? It would also seem that pumice, scoria, etc. would all have very low buffer capacities.
Any thoughts?
Is there anything important to say about buffer capacities of the various substrates? (Especially for those of us with hard water)
Buffer Capacity as "reserve acidity is the concentration of hydrogen ions attached to the negatively charged clay particles and organic matter. This is measured as buffer pH. Buffer pH relates to buffer capacity of the soil: ability to resist changes in pH." - http://www.isafarmnet.com/ResearchPublications/06Nconf/E1.pdf
It would appear that akadama has some buffering capacity based on the presence of clay minerals (allophane complexes) and humus which you have previously highlighted. Although my SWAG (scientific wild-ass guess), is that it would be lower than peat and probably lower than pine bark. However is this buffer capacity and the expected higher buffer capacity of Kanuma one of the reasons it is recommended for azaleas? It would also seem that pumice, scoria, etc. would all have very low buffer capacities.
Any thoughts?
markyscott
Imperial Masterpiece
Hi Hemmy -
I have heard kanuma described as acidic and I've seen some references that purport to have measurements that support that claim. Pumice and scoria are glass and thus pretty non-reactive, I imagine, unless there are some alteration products present.
But, in short, I have my doubts about how much all of this matters. Earlier in this thread I wondered how important the soil pH was in bonsai culture. I'm not sure that anyone knows, but we can conjecture a bit together on the matter. Here's the issue as I see it:
Measuring soil pH is pretty simple. Take a few grams of kanuma or akadama and powder them. Then mix it with DI water in a beaker and let it equilibrate for a couple hours. Then repeat with pH 10 solution. The issue I have is this (and I freely admit that I don't know that answer) - we use some pretty coarse grains in bonsai which minimize the reactive surface area with the water. And then we flush several soil volumes of water a day through the pot. For instance, in the summer I water trees 2-3 times a day. Each time I water I flush 2-3 pot volumes of water through the soil. So each day the soil sees up to 10 times its volume in water. This is not like our garden. Isn't the pH of the water we're using the more important thing?
But I don't know - perhaps the soil is more reactive than I imagine and it's buffering capacity much larger. What do you think?
Scott
Some time ago I found a nice article about managing soil pH from the University of New Hampshire and it boils down to using the right fertilizer in our soilless media and frequently checking the pH. I am also not a fan of using rainwater to be honest, both because of its low alkalinity and because of the storage conditions often favoring microbial growth or cross-contamination between plants. (But I live in an area with great tap water for growing plants.)
hemmy
Omono
You are probably correct that the irrigation water is the more important factor. After re-reading some articles, specifically Dr. Whitcomb's (Okie State and Rootmaker pots) article "The pH Factor". He describes an experiment where he watered 30 containers of commercial potting mix (pine bark, peat, & sand) with water of pH 3.0, 7.0, and 11.0. It took 26 days for the substrate pH to match the water and 4 months when the experiment was run again on potted plants. So even materials with assumed high buffer capacities and low starting pH (pine bark and peat). We can probably assume that our mixes match our irrigation water in pH (acidic fertilizers aside). Instead of measuring the buffering capacity (as discussed in the link in my previous post), it might be more interesting to measure the pH of the leachate from the pot to see how closely it matches the irrigation water pH.
As you pointed the volumes of water used probably negate any buffering effect of the substrate. But the high pH of our water is only the symptom of high TDS or elevated levels of calcium and magnesium. Knowing those levels and how to mitigate them is probably the more important factor, which has been discussed elsewhere and is a topic for another thread.
Thanks for reply!
markyscott
Imperial Masterpiece
I've posted a new resource documenting the theory and physics that we discussed in this thread. Enjoy!
Gustavo Martins
Omono
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.
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.
...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.
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.
jacob letoile
Mame
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
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
Gustavo Martins
Omono
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?
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?
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