Diatomaceous Earth C.E.C. and WHC?

[Scrixx]

So I've tried to find the CEC and WHC of Diatomaceous Earth but had no luck. Does anyone know what the values are? Still new to bonsai and I wanted to learn about each soil component and why they are used. There are information about all the other components except DE.

I was going to do 100% DE as my substrate since I live in zona 10a in Southern California. It's dry and hot here. Though I read about some people having problems with 100% turface and am worried DE will have the same problem. That's why I want to know the CEC and WHC so I can compare them better. The best information I found was that DE holds "a lot" or 6x it's weight in water. Looking for the answer in volume.

I'm probably overthinking my soil mix but it would be good to know.

Here's one of the sources about CEC, WHC, pH of other components. I found similar values elsewhere online so it should be good for our purposes.

Here's the thread where I found the WHC in volume of some of the soil components.

Thank you.

 

[jacob letoile]

If you look at the top of the page, there is a resources button. One of the resources is Introductory Soil Physics. In that document is a methodology to determine the water holding capacity of any soil you like.

 

[sorce]

Welcome to Crazy!

Sorce

 

[Scrixx]

If you look at the top of the page, there is a resources button. One of the resources is Introductory Soil Physics. In that document is a methodology to determine the water holding capacity of any soil you like.

Looks like I'll do that!

 

[0soyoung]

I've seen the CEC of DE reported to be about 27. Turface, a calined clay is spec'd to be 33. Akacama is close to the same (every discussion of bonsai substrate must include akadama, in case you didn't know ).

 

[jacob letoile]

http://jjsminerals.com/pdf/DIATOMITE_HYDROPONICS_STUDY.pdf

If you scroll all the way to the bottom, it has a chart listing the cec as 2.7 and 3.0. Not sure how valid those numbers are. Maybe @markyscott Can answer?

 

[Stan Kengai]

As far as substrates go, 100% of anything is usually not ideal. Different particles have different functions within a mix. Pumice is, by far, a superior substrate to both DE and Turface, and it can usually be had for a reasonable price. Search for Colin Lewis's articles on bonsai soil for a pretty comprehensive analysis of materials. But keep in mind the differences between his climate and your own (that also goes for info/advice given by others here and in other resources).

 

[Scrixx]

http://jjsminerals.com/pdf/DIATOMITE_HYDROPONICS_STUDY.pdf

If you scroll all the way to the bottom, it has a chart listing the cec as 2.7 and 3.0. Not sure how valid those numbers are. Maybe @markyscott Can answer?

That seems low and also it says cmol / kg which is different than the usual measurement of meq/100g. Maybe someone can convert it for us?

I've seen the CEC of DE reported to be about 27. Turface, a calined clay is spec'd to be 33. Akacama is close to the same (every discussion of bonsai substrate must include akadama, in case you didn't know ).

I think I found the source where the CEC of DE was reported to be 27. It might be right because turface and akadama are both made out of SiO2 and have similar CEC. Even though Turface has 15% more SiO2.

 

[Scrixx]

As far as substrates go, 100% of anything is usually not ideal. Different particles have different functions within a mix. Pumice is, by far, a superior substrate to both DE and Turface, and it can usually be had for a reasonable price. Search for Colin Lewis's articles on bonsai soil for a pretty comprehensive analysis of materials. But keep in mind the differences between his climate and your own (that also goes for info/advice given by others here and in other resources).

Yeah I messaged markyscott and he told me pumice is commonly found in the west coast. I thought the cheapest was 7$ per gallon shipped from a website but after I talked to him I looked again and found some nearby for 3$ a gallon! Glad I have access to it. I've ready very good things about pumice.

 

[Scrixx]

Welcome to Crazy!

Sorce

Thank you, glad to be here!

 

[Scrixx]

Okay so I did the porosity and WHC experiment on my diatomaceous earth, napa oil dry #8822. I'm not sure why some pictures are sideways while the some are fine. Now I had to make do with what I had for measurements so the results will be very rough.

Grain size is .1" to .2" or 2.54 mm to 5.08 mm

So here I measured out 500ml of DE and water.

IMG_9785

• Scrixx
• May 3, 2017

How much water was left

IMG_9786

• Scrixx
• May 3, 2017

Water filled to the top of media

IMG_9787

• Scrixx
• May 3, 2017

I had to measure the volume of water with cooking measuring tools.

IMG_9789

• Scrixx
• May 3, 2017

Water that drained out of the media.

IMG_9790

• Scrixx
• May 3, 2017

Since I measured in teaspoons, tablespoons and cups. I'll convert them to ml so I don't have to list them.

The water that remained after the initial filling is 206.3 ml so the amount of water used is 293.7 ml. So porosity is 58.74%

The amount of water that drained is 79.72 ml. That means the amount of water that remained is 213.98 ml. With these values we find that our air filled porosity is 15.94% while our water holding capacity is 42.80%.

 

[markyscott]

Okay so I did the porosity and WHC experiment on my diatomaceous earth, napa oil dry #8822. I'm not sure why some pictures are sideways while the some are fine. Now I had to make do with what I had for measurements so the results will be very rough.

Grain size is .1" to .2" or 2.54 mm to 5.08 mm

So here I measured out 500ml of DE and water.

IMG_9785

• Scrixx
• May 3, 2017

How much water was left

IMG_9786

• Scrixx
• May 3, 2017

Water filled to the top of media

IMG_9787

• Scrixx
• May 3, 2017

I had to measure the volume of water with cooking measuring tools.

IMG_9789

• Scrixx
• May 3, 2017

Water that drained out of the media.

IMG_9790

• Scrixx
• May 3, 2017

Since I measured in teaspoons, tablespoons and cups. I'll convert them to ml so I don't have to list them.

The water that remained after the initial filling is 206.3 ml so the amount of water used is 293.7 ml. So porosity is 58.74%

The amount of water that drained is 79.72 ml. That means the amount of water that remained is 213.98 ml. With these values we find that our air filled porosity is 15.94% while our water holding capacity is 42.80%.

Nice job, Kyle. For your reference, 16% is a low AFP. What is the height of the soil in the container?

Scott

 

[Scrixx]

Nice job, Kyle. For your reference, 16% is a low AFP. What is the height of the soil in the container?

Scott

Thank you Scott. That's exactly why I wanted to know the AFP and WHC. To avoid problems like that.

The height of the soil in the container is 2.25 inches or 5.72 cm.

 

[0soyoung]

This test (nicely done btw, @Scrixx) was done with a wide shallow mass of substrate, so the results are or could be strongly influenced by the saturation layer. @markyscott's tests were done with a narrow and tall graduated cylinder so the saturation layer represents a smaller amount of the total.

If repeated with half, say, the amount of DE, you should find AFP to be even smaller. If you could do it with, again say, 50% more substrate, you should find the AFP to be larger. These two additional measurements might be enough to deduce the saturation depth and the AFP in the DE above that level (but it likely takes more data).

 

[milehigh_7]

BTW 8822 is calined DE but not all DE is, does that throw a wrench into things? ;-)

 

[Scrixx]

This test (nicely done btw, was done with a wide shallow mass of substrate, so the results are or could be strongly influenced by the saturation layer. Tests were done with a narrow and tall graduated cylinder so the saturation layer represents a smaller amount of the total.

If repeated with half, say, the amount of DE, you should find AFP to be even smaller. If you could do it with, again say, 50% more substrate, you should find the AFP to be larger. These two additional measurements might be enough to deduce the saturation depth and the AFP in the DE above that level (but it likely takes more data).

Nice, thanks for the explanation. I understand the relationship between height and AFP/WHC better.

Wouldn't this test be a better representation of a soil in a bonsai pot because it is wider and shorter than a graduated cylinder? When directly compared to Scott's data it would not be a good comparison because we lost the control of the height and radius of the container. I will do the experiment on future soils I get with the same container for consistency. It might be next year at the latest because I'm not looking to repot just yet. Started the hobby when spring already started.

BTW 8822 is calined DE but not all DE is, does that throw a wrench into things? ;-)

I can't seem to find where it says calcined in that document but good point. I'll clarify the experiment to state calcined DE along with the brand name. I'm assuming it's calcined because it doesn't break down easily. The most common DE recommended online in the USA is Napa Oil Dry #8822 so I think it'll help people get a general idea of the properties. Since it's the most commonly found DE source online I'm assuming a lot of people use it as well, in the USA at least.

 

[0soyoung]

Wouldn't this test be a better representation of a soil in a bonsai pot because it is wider and shorter than a graduated cylinder? When directly compared to Scott's data it would not be a good comparison because we lost the control of the height and radius of the container. I will do the experiment on future soils I get with the same container for consistency.

Certainly your test is a better representation. However, it would be better if we knew the saturation depth and AFP independently. Then we could easily compute the effective AFP for any pot.

The one criticism I have of @markyscott's soil physics is that it neglects the saturation depth. Since both saturation depth and AFP are easily conceptualized in terms of spaces between grains, they are likely linked to the grain size of any one specific substrate. However, I/we have no (quantitative) idea what saturation depths are whereas Scott has given us a lot of data on AFP for different substrates and grain size. I may get off my duff and do some tests with Turface in the next few weeks so that I offer something more than proselytizing.

 

[markyscott]

Certainly your test is a better representation. However, it would be better if we knew the saturation depth and AFP independently. Then we could easily compute the effective AFP for any pot.

The one criticism I have of @markyscott's soil physics is that it neglects the saturation depth. Since both saturation depth and AFP are easily conceptualized in terms of spaces between grains, they are likely linked to the grain size of any one specific substrate. However, I/we have no (quantitative) idea what saturation depths are whereas Scott has given us a lot of data on AFP for different substrates and grain size. I may get off my duff and do some tests with Turface in the next few weeks so that I offer something more than proselytizing.

Measuring the height of the saturated layer is challenging in a garage experiment, partly because it's not a boundary. There's an increase in saturation with height from the base to the top of the soil and a zone at the bottom where the saturation is 100%. My approach was to pick a substrate and measure average AFP as a function of height. That works pretty well, but with this approach, short columns mean you start dealing with extremely small volumes of water and measurement becomes a problem. Kyle's approach involves larger water volumes, perhaps making this easier. As you approach the saturated zone, the AFP goes to zero and the WHC approaches the porosity, so, theoretically no water will drain out under gravity.

 

[63pmp]

There are no drainage holes in your test pots. Your results are fairly meaningless. The saturation zone at the bottom of pots is totally depended on particle size. Air filled porosity increases as pot depth increases so your tests should be done on the same depth as your avtual growing pots. You must have holes in the bottom so proper drainage can occur. tipping water out changes the depth of the soil profile changing drainage behaviour of the mix.

 

[Scrixx]

There are no drainage holes in your test pots. Your results are fairly meaningless. The saturation zone at the bottom of pots is totally depended on particle size. Air filled porosity increases as pot depth increases so your tests should be done on the same depth as your avtual growing pots. You must have holes in the bottom so proper drainage can occur. tipping water out changes the depth of the soil profile changing drainage behaviour of the mix.

The experiment was performed similar to Scott's tests. Except I used what I had laying around. There were five drainage holes spaced out and covered with tape. The tape was then removed after the initial filling and the container was placed on top of two barbecue skewers to hold it horizontally while it drained. This was just one test and my method would only give a rough estimate on WHC and AFP. It's enough for my purposes.