Severe Root Burn

[orchids3]

Hi Interesting thread. What percentage by weight does "Prime Agra" retain? (Maybe Ray Knows) My experience has been that more roots are burned or destroyed by acid levels in the pots than any other reason.

[Becca]

Ray I've used the directions on your website for presoaks and have soaked multiple times before using...I've even tried changing out the prime agra (again I followed presoak procedures) and I still have the same problem. I also use RO water (bought the system from you!). So am I wrong on my thinking of what is causing my problem?

[Ray]

As I said before - it's either fertilizer minerals or plant waste products.

If your growing environment favors evaporation, it will happen faster, no matter what it is.

I have no data on the retention of minerals by PrimeAgra, but it should be lower than any other absorbent medium.

[Jerry Delaney]

On the other hand, the pH in the reservoir will change drastically as a result of the plants' biological processes. A few years ago, several of us tried measuring the pH, and found it to be as low as 3 or 4, especially first thing in the morning, after the respiratory processes dumped all that CO2 into the root zone. THAT'S why I insist that folks fill pots rapidly to the top and let it drain, so the reservoir gets flushed and the chemistry returns to normal. Topping up just dilutes the bad stuff a little, and plugging the holes for a while just mixes it with new solution.

Ray, help me out here. I think I understand what you are saying. However, I have been following a group of plants in S/H for about 5 months or so that have Multicote as their sole fertilizer. None of the plants are in Prime Agra, and I have dropped the tests to once a month since the readings were so stable. I have not seen any of the samples from the water in the pot lower than 5.5. Is it possible that the higher pH indicates some lack of nutrient? The physical growth seems no different than those planted in my regular bark medium. Also,

I have no data on the retention of minerals by PrimeAgra, but it should be lower than any other absorbent medium.

I'm afraid I don't understand. Why should it be lower than any other absorbent medium. Thanks for the help in advance Ray.

[bast]

Originally Posted by Jerry Delaney

Ray, help me out here. I think I understand what you are saying. However, I have been following a group of plants in S/H for about 5 months or so that have Multicote as their sole fertilizer. None of the plants are in Prime Agra, and I have dropped the tests to once a month since the readings were so stable. I have not seen any of the samples from the water in the pot lower than 5.5. Is it possible that the higher pH indicates some lack of nutrient? The physical growth seems no different than those planted in my regular bark medium. Also,

The variation of pH can be linked to the type of fertilizer, some are more stable to keed pH as you set. When the biologycal process occur. Meaby by adding product that having a better tampon efficiency...



I'm afraid I don't understand. Why should it be lower than any other absorbent medium. Thanks for the help in advance Ray.

About the primeagra, if just a support for the roots of the plant. It not the same thing as organic substrat where minerals can be link.


I grow lot of my orchids in woolrock and it the same problem. Some other guy have the problem with the drop of the pH, and that dreak down the rockwool.
i will try to use fertilizer having low NH4. And i wont to get some product from dynagrow the keed the pH more stable. But i don't remember the specific name.

I hope my english was understaneable!!! I'm sorry l'm french.

[Ray]

Jerry,

Using a fertilizer solution, it goes into the pot with "composition A". As the plant takes up nutrients, it discharges stuff into the solution, both ions in solution and gases - no more "Composition A", but something entirely different. That won't improve until you replace the solution with fresh stuff. I would bet the Multicote is stabilizing the solution pH, so you simply don't see the swings.

Concerning the lower buildup in PrimeAgra:

In the "ideal" potting medium particle, everything that is absorbed will be released again. Unfortunately, "real" particles don't release 100% of what they absorbed. The difference between the two is termed the "hysteresis". The greater that hysteresis, the more is left in the particle, hence the greater rate of buildup.

The size, shape, and distribution of pores, and the materials surrounding them determine how completely the absorbed solutions are released again.

Nature decides all of that in organic media, and stuff like diatomite, but it can be controlled in charcoal (horticultural charcoal isn't well-controlled, but activated charcoal is), and in man-made particles like LECA.

The clay used for most European LECA brands is fairly equivalent, but the engineering used to compound, form, and fire them isn't, and that's where the differences come from. PrimeAgra is the only brand that was specifically engineered for horticultural use (rather than being a remarketed concrete aggregate), and minimizing the hysteresis was one of the design criteria.

[Jerry Delaney]

I would bet the Multicote is stabilizing the solution pH, so you simply don't see the swings.

I sure hope that is the case Ray, I certainly hope it’s not a case of insufficient nutrient that is limiting the pH drop. Or, I guess I could always hope it’s because I don’t get up early enough to sample while the pH is still low!! I also will have to confess that I am not using really great technology to do the measurements. My main concern was to measure the nitrogen level but I am just too cheap (I mean frugal) to bust loose with the money to purchase any kind of equipment that might give (more) accurate results. I have just been using the “dipsticks” used to monitor ponds (pH, total alkalinity, TDS, NO2 and NO3). Problem is that they only measure up to 200 ppm of NO3 which I make out to yield a total nitrogen level of ~45ppm. In reality I can only say that it is equal to or greater than 45 ppm since the color change is past the charts maximum range. The strips do seem to come close on pH since I always include my tap water as a control and it is usually within 0.1 – 0.2 of my pH meter reading.

The size, shape, and distribution of pores, and the materials surrounding them determine how completely the absorbed solutions are released again.

I notice your use of the word absorb. Is there any ionic bonding between salts in solution and the surface of the clay aggregate?

Thanks for the explanation Ray

[Ray]

I think that the fired clay has essentially no potential for ionic bonding with mineral salt ions - something referred-to in horticulture as the "cation exchange capacity", and all of the absorption is related to sponge-like porosity.

When you fire a ceramic body the surfaces of the silicate materials tend to get "fluxed" by the alkaline components, forming a glass that bonds them together, and pretty much tying up the ionic bonding sites. Then, water has the propensity to bond very strongly to those few, remaining ones, essentially shielding them from further activity.

[Jerry Delaney]

Thanks for the info Ray. All this brings up about a zillion questions I’d like to ask but don’t think my mind will assimilate the information these days. I know that there are some types of clay, i.e. kaolin, that have the ability to non specifically adsorb proteins and lipoproteins, but this clay is completely different from the type of clay used for LECA’S. Even then, I don’t think the adsorption is ionic in nature but most likely van der Waals attraction. Golly, Ray, I just can’t seem to remember all this; it was a couple of lifetimes ago.
What you say about the fired clay makes some sense. In many of the biological assays we used to run, we often found we had to be quite careful NOT to use plastic lab ware i.e. pipettes, test tubes etc., due to adsorption of protein molecules onto the plastic. Most of the time, Pyrex or borosilicate glass didn’t seem to have this problem. Again, this was most likely due to van der Waals forces, not ionic bonding.
I’m afraid these days, I’d best just concentrate on “green side up”!!!
Again, thanks Ray.