They both can work, some like one over the other. Both are used a lot in horticulture. I like DE better it holds more water. Same variation can occur when heat treated, so products can vary.

Fievel,

A few moments ago I posted a reply in another thread about this. I have not used Turface in any large-scale container soil mixes but I have tested Moltan OptiSorb oil absorbent. It is stable, has a larger particle size than Turface and NAPA Floor Dry, and provides moisture to plants without holding perched water.

If you wish to try some as an experiment I encourage you to do so.

TYG

I have tested UltraSorb (DE).
One unit weight of it absorbs equal to its weight in water. i.e, one oz of it absorbs one oz water. And it does that without increase in volume.
I also froze it (fully saturated) and then thawed. It did not break/fall apart.

So I think it is good moisture retentive. And once saturated will act like perlite.

Seysonn

In my experience, Turface can turn Chicago tap water from pH of around 8.3, to pH in the low 4's. Calcined d.e. by Axis/Envirotech brings the same tap water pH down to the mid 5's.

The claimed cec for the Axis calcined d.e. is 27, but they tell me they've seen it as low as 5 or 6 due to variability of the moisture of the incoming raw material, and the way that affects the firing requirements to achieve the calcining specs. In plain words, plants need some component other than calcined d.e., to hold nutrients.

Turface claims cec of 33. The company says it can vary, but being clay, the cec would vary within a more narrow range. Clay is decomposed granite, and the low pH is due to the aluminosilicate from the granite, which affects the cec. In plain words, calcined clay such as Turface holds nutrients for plants, on its own, without organic matter.

There are very real differences in product specs and quality controls among vendors in each category, which complicate the comparisons. In my opinion, we shouldn't hang our hats on evaluations that are based on products NOT specifically made for horticulture.

Anyway, I haven't grown in the d.e. yet, but seems to me the d.e. has the right pH effect, good water holding, and I haven't made up my mind regarding its stability over time, but has potentially poor nutrient holding capacity.

I have grown in Turface based mixes, as well as pure Turface; seems to me to have decent water holding, holds nutrients just fine, doesn't break down easily, but can be too acidic on its own, without dolomite. I have had issues with it in the past, when I used too much dolomite lime, mainly when in combination with pumice, which can be quite alkaline.

FWIW.

I always have compost in my mixes so I'm not worried about nutrients being
held. Not sure how turface holds anything with such a small pore size? Plants
can't utilize even water from turface until capillary action pulls it out.
Untrue with DE, which pores are large enough for roots to enter. Many disregard
the well documented pore size, but I can't dismiss that by anecdotal evidence
alone.

You sure have no problem dismissing the experimental data that I posted ages ago showing plenty of plant available water (PAW) from turface based on well not much at all except the hypothesis that the pore size will trap all the water.

I believe the O. P. asked for experiential examples that would indicate the superiority of either calcined d. e., or Turface.

I just put forward what I've experienced so far, together with some info I got directly from technical folks at Turface and Axis. The Axis rep even suggested including crushed basalt, as a way to mitigate the poor cec of the calcined d.e.

cec, or Cation Exchange Capacity, relates to electrical charge. Calcined clay holds nutrients on cation exchange sites which are not limited to pores. Just look at the salt build up on your clay pots, for example.

I will add this: Napa Floor Dry #8822 is a poor representation of calcined d.e. It turns to mush quite easily. Maybe it was just the bag I got, but based on that, I would never in good conscience recommend anyone try to use it to grow plants in. Not sure how that became such a highly recommended product around here.

That was the same as my experience with Napa Floor Dry. I did a search on the web and came up with a few people with the same experience and lots more that found it worked well. I believe there are 2 suppliers of the same material that don't matter when you use it to dry oil from floors but make a big difference when you use it for potted plants.
You can test it first. The stuff I tried failed pretty quickly in a cup when filled with water and left sitting for a week.

As an experiment, I have two citrus growing in almost pure Turface that are doing well. That is an experiment, not a recommendation.

This reminds me of some folks saying any dish detergent will work as well as the high-priced insecticidal soap, which ignores the fact that-just for purposes of this discussion-let's say Proctor and Gamble are making their dish detergent brand A, using ingredient C one week, but that next week, ingredient D becomes more economical. Guess what? That dish detergent is not the same as it was a week ago. Now, for certain I'm making this stuff up, including pulling names and numbers out of my posterior, but it is to make the point-we all like to save $$ via using non-specific items for our specific purposes. Sometimes it doesn't matter, but then other times, you can run into trouble.

+oM

lunarsolarpower - when reading your information above, it seems to disagree with this statement from Al (tapla): "The differences that are important: Calcined DE has greater internal
porosity and thus more surface area, so it holds more water and has more
attachment sites for nutrients (better CEC - cation exchange capacity).
DE is just a little lighter when dry, but about the same weight as
Turface when wet. DE has a pH of about 7.0, while Turface comes in at
around 6.2." from the thread here: http://forums2.gardenweb.com/discussions/1397698/alternative-to-turface

I'm mainly concerned about the CEC discrepancy.

I'm looking to make an inorganic mix for longer-term use (a decade or more), to grow vegetables in central Ohio 6a. I'm interested in using the Calcined DE as a primary component and amend it with other inorganics.

My questions:

With a higher CEC would rain NOT flush the fertilizers out of the growing media?

Would zeolite and Calcined DE work to improve the CEC?

Maybe the CEC doesn't matter if I'm using controlled release fertilzer granules or applying a full-range liquid fertilizer at least weekly?

Many thanks for the thoughts.

gregbradley, I just bought a bag of NAPA floor dry and am testing it out in a cup of water, we'll see how it goes...

Hi Strings,

The statements in that thread are six years old. I'm absolutely certain Al's statements were accurate at the time.

The way these products are produced has certainly evolved, and probably the characteristics under discussion here have changed or "improved" somewhat. For example, today's version of Axis calcined DE, cubic foot per cubic foot - according to the folks at Axis - is about half the weight of calcined clay, at "dry" weight. Obviously, that differs from Al's info of six years ago, and probably reflects an improvement of the DE product over the years.

In addition, folks should try to understand, the raw materials that go into these calcining operations vary, and calcining specs also vary, which means the end products will not be perfectly uniform from batch to batch, or over time.

The pH of Turface is low because clay has aluminum in it. The more aluminum, the lower the pH, and chemical composition of clay varies across deposits. Turface clay comes from more than one deposit.

Not that I'm an expert on any of this. Please note in my posts above, that I'm sharing information given by technically knowledgeable representatives at the companies who make Axis and Turface. Some of this in phone calls, some in emails. None of this is my own info.

One piece of information I did verify on my own, was the pH of Turface, which I actually heard from Bonsai Jack. I then checked the pH for myself, and found the pH was indeed around four. Then, I had my own observations verified by a Turface technical employee, who then also verified the cec. This is the way I like to operate. I hear or read something, I test the thing in my own experience as best I can, and then I get expert independent input, for perspective and information on my observation or result - BEFORE I put things in writing.

I figured since I've received benefit from Al and others around here, I could share some of what I find out from qualified folks I talk to along the way, when the info seems helpful to folks here.

I encourage everyone reading this, to do their own pH testing, and always "follow the money" when it comes to fact checking information, by going to expert sources if in doubt.

By the way, in comparing calcined DE and Calcined clay for cec, the porosity is a factor, but so is the density of exchange sites.

If two materials have the same exchange site densities, and same particle size, the one with the higher porosity value will have the higher surface area - and cec value. In diatomaceous earth vs clay, diatomaceous earth has lower average exchange site density.

You are onto something, though. DE may hold nutrient less tightly, but it will hold it in a larger reservoir of capillaries.

"Larger CEC values indicate that a soil has a greater capacity to hold
cations. Therefore, it requires higher rates of fertilizer or lime to
change a high CEC soil.

The particular CEC of a soil is neither good nor bad, but knowing it is a valuable management tool."

http://www.spectrumanalytic.com/support/library/ff/CEC_BpH_and_percent_sat.htm

Considering this info, Sounds like DE is just about right!

lunarsolarpower - thanks for the replies and further information & clarification!

drew51 - I hadn't thought of the disadvantages to high CEC, I appreciate the link.

Turface claims a cec of 33. Axis can vary from 5, to about 27. The crushed basalt in my possession has a cec of 140, according to the company it came from. According to Wikipedia, humus cec ranges from 100 to 300.

I would hesitate to call 33 a high cec, though certainly not low.

If you read that article drew linked, you will find that higher cec soils hold more nutrient in reserve, which means more nutrient available to the plants when they need it. It also means pH will fluctuate in a narrower range, and balance out quickly. Your plants will be more resilient, with less effort. You will also find in that article, that lower cec soils are prone to leaching, particularly nitrogen leaching, AND the pH is subject to changes that don't rebound on their own, or do so only partially, and very slowly. Your plants will be less resilient, and more effort will be required, with small margin for error.

IMO, a higher cec is no problem. The growing medium will load up on the fertilizer you provide, and release it as the conditions warrant. No big deal. Higher cec is a non-issue.

Low cec means little to no pH buffering, little to no nutrients in reserve, and ultimately, leaching of nitrogen. Low cec produces issues you must carefully manage, likely on a near daily basis. You are, by definition, growing in a nutrient deficient medium.

As intellectually stimulating as this conversation is, I doubt any of us will be growing anything in pure calcined DE. However, if someone does, this conversation provides a nice heads-up, to pay very close attention to their pH and fertigation controls.
FWIW.

Their is a thread on TV about growing in pure DE, so it is done by some all the time. I myself would not. I disagree a little about a high CEC making nutrients available, if the soil is nutrient poor, a high CEC is going to require more nutrients, as one must first reach the proper saturation. The article no way implies that the reserve is available to the plant. Just the opposite actually, it is not available. Just like phosphate,nutrients can be held in place and not available to the plant. The article also states low CEC soils have low water holding capabilities, yet DE holds more water than turface, so why it has a low CEC is confusing to me. I use organic fertilizer and soils with a low CEC are going to make nutrients available as the organic breaks down, so the breakdown rate of the organic gives me the time schedule as to when to fertilize. I don't have to guess if the soil is saturated enough in a high CEC environment that the release actually feeds my plant.

Low CEC soils usually have poor water holding capability because those soils are most likely sand with no organic matter. They don't have low water holding capacity because of the low CEC. It's just that high CEC correlates with what is missing, clay and OM.

Drew, surface area and cation exchange site density are discreet properties. One is a structural property, the other is chemical. Porosity is structural.

So, yes, in a given lot of clay or DE, as surface area increases by porosity, so does the cec. Increased surface area simply exposes more cec sites.

Here's the fun part: The chemistry of the material is one limiting factor, but the characteristics of the porosity in the material, is another. All else being equal, large pores expose LESS surface area than fine pores.

Calcined DE has larger pores, and larger internal volume, but less available surface area than Calcined Clay, with its finer pore structure.

Now, here's something to mull over - cec is calculated as the exchange of cations in the soil solution, i.e., in water available to plant roots. The indication is, while calcined clay has less internal volume, than calcined DE, water in the Turface calcined clay pores IS available to plants - there's just less volume there.

Drew,

I don't see how one can say, a higher cec leads to a nutrient reserve, but the fact of a nutrient reserve is evidence that those nutrients won't be available to plants.

We're talking about cec nutrient reserve, in a gritty mix. Cec is like a surge protector/battery backup combo. Plug the backup power into the wall, plug your computer into the backup power, and forget about it. It charges itself as you use it. It keeps the voltage to the computer in a narrow, optimal range. During the occasional outage, it keeps power going to the system, and when the outage is over, the battery recharges itself.

It's simple, really. Just fertigate. The reserve charge takes care of itself. The media volumes here are low. These are plants in pots, not corn in a field.

Stringz,

Sorry I got sidetracked on some of your questions.

Vegetables in containers - Not something I have a lot of experience with, so grain of salt, okay?

Effect of cec on nutrient leaching during rains - the only way I know to be sure, is to invest in a quality electrical conductivity and pH meter. Surely, there's leaching. My guess is higher cec media would certainly help pH recovery cycles, working with the crf. Until you had the opportunity to fertigate again. Higher cec also facilitates chelation of minerals by organic acids. My guess is, in the end, there will be little performance difference during periods of persistent rain, between higher and low cec media, in containers.

I will say that last year, I tried tomatoes in 511, and it didn't turn out well at all. I decided to rely completely on liquid fertilizer, and then had one of the the wettest spring and early summers on record. My containers were waterlogged for weeks on end. Crf would have saved my bacon.

I don't use zeolites, so can't help you there. I looked at them once, but found myself distrustful of the enterprise, not due to lack of promise, but due to the highly specific nature of zeolite affinities, and utter lack of assurance that what was in the bag was what was expected, or even the same as what was in the last bag of the "same" zeolite.

The cec raising question. For containers outside, I would consider calcined clay over DE, for reasons in my other posts above.

I don't see you getting ten years of vegetables out of the same media in containers, though. Even Turface calcined clay breaks down eventually, and in my limited experience with it so far, Calcined DE is generally softer than Turface.

LunarSolarPower - Thanks for coming back to my questions, I appreciate your responses.

As I'm probably overthinking the CEC impact in my intended use (vegetables in containers), but I do like to optimize systems for efficiency and highest performance, so it was a natural question for me to follow.

I'm under the impression that by using CRF and a liquid solution, I'm in a good position to provide what the plants need with little regard for the CEC.

My question about the zeolite was to raise the CEC, and in fact, you mentioned in an earlier post about ground basalt, so if I decided to go that route, I could always look more closely there as well.

As to getting 10 years out of the media - I can always dream, can't I? :) It appears inefficient (on the convenience and labor sides) to mix new media every spring. It seems wasteful to the product as well - I have limited ground space, and who knows what I would do with the "old" mix. There is always the cost aspect as well.

My primary thought was to go fully inorganic and have nothing that decomposes within 5-10 years.

But, even if I ended up going with some organics as a fraction of the mix, I'm thinking that if I maintained a reasonable particle size with the inorganics (say Turface/DE/pumice/grit), AND as long as the combo of inorganics comprised the lion's share of the mix (say ~70%), then the organics would be free to decompose and disintegrate their structures without much harm overall.

I could simply "top off" the organics (for instance pine mini fines) as needed to keep the overall volume of media to my liking.

If CEC value is not critical in my specific scenario (vegetables in containers, using CRF and liquid fertilizers), and assuming I'm able to relatively easily adjust the pH as needed, then I would be able to design the mix primarily on water/air retentiveness.

Do you see any faults in the logic so far, or glaring oversights with such a plan?