LECA vs Lava rock - salts accumulation

[DavTom]

Hi Ray, hi all,

I saw this post "LECA Comparison Study 2020", I visited the website and I found it very interesting and useful. (I am creating a new thread here as I think that that thread is closed (i.e., it is not possible to post any replies to it)).

I am currently using lava rock with a few Phals in semi-Hydroponics and LECA seems to me a good alternative as it gives me the feeling that it can retain moisture a bit better as it expands a bit with water and that the spacing left for the roots is given with high accuracy by the chosen dimensions of the spheres, while with lava rock it varies as it depends on the irregular size and shape of the rocks. I also assume that LECA weights less; a lava rock pot can become quite heavy...

I have also read many other pages in Ray's website (and I plan to read it all very soon!), including some statements that lava rock is not so good as medium as it accumulates too much salts. I would like to understand the rationale for these statements as:
- If lava rocks accumulates too much salts, why does LECA not? My assumption is that you need a medium with high porosity/surface in order to retain as much water as possible. Since I assume that both LECA and Lava rock are very porous with a lot of surface, if one accumulates too much salts then I would expected that the other would do it as well. Or am I missing something here?
- Since more than a year I am growing a few Phals in Lava rock, with supplemental light in winter, feeding them every week regardless of season alternating two solutions: week#1 Sol a) N 120 ppm and all the other macros in proportion to that; week#2 Sol b) only micros, an so on so forth every week without missing one single week of fertilization. I use RO water and a soak the pot between 12 and 24 hours when I feed the Phals.

My assumption, correct me if I am wrong, is that Sol a) is a bit on the high side for its concentration of nutrients, and this seems also confirmed by the TDS reading of the solution between 600 and 700 ppm. Despite that, I do not see any accumulation of dray salts on the lava rock when the rock dries; Once every couple of months I do the following test: I leave the pot soaked for 24 hours in plain RO water after applying Sol a). The TDS reading after 24 hours is about 15ppm and the the reading of the RO water is 9 ppm: so there is close to zero leakage of dry salts from the lava rock back to the RO water, right?

Maybe, swapping Sol a) and Sol b (the latter has a very low TDS) does the trick flushing every other week the accumulation of dry slats caused by Sol a)? If so, this seems a very easy solution in order to use lava rock without salts accumulation. In addition micros are much more readily available for absorption by roots if they are not mixed with macros (e.g., iron tends to easily precipitate out of solution if PO4 is present in the same solution, especially at high PO4 concentrations). And all the work to get the right PH stuff (i.e., the sweat spot of PH 5.8) really matters only for micros (Phosphorus is even not so available at PH of 5.8). So, by swapping sol a) ad sol b) you get also the following advantages: 1) you test PH only when you feed the micro solution (i.e., less work); 2) you get iron (and other micronutrients) and well as the macronutrient Phosphorus more available to the roots.

I would appreciate very much your thoughts as I want to try soon LECA, but I have first to understand the salts accumulation aspects. I want to be sure I am not missing anything important here. All what I wrote above makes sense to me, but who knows for sure? Not me...

Thx.

Cheers,
Dav

[Ray]

The reason I deemed lava rock to accumulate more salts is partially due to my own experience, but also due to the structure of the porosity.

Lava rock is formed from a viscous liquid, and the pores formed when it outgases. Because of that, the internal pores tend to be large and have thick walls, connected to the surface via microcracks. A dry piece will absorb like a sponge, but the liquid that fills the voids tends to sit there, and once it's dry the solids are trapped. Rewet it and they absorb more liquid, repeating the cycle, with very little extraction.

LECA is made from powders and is sintered. The particular brand I was using the most had fine porosity, connected in every direction with similarly fine gaps between the particles. Communication with the surface occurs more freely.

That said, there are lots of different forms and chemistries of lava rock, and lots of different brands of LECA, each with its own properties, so while my assessment of the physical structures is fairly broadly applicable, it seems likely my earlier, published conclusion was based upon a narrow sample set.

Don't forget that, back then, the article was as much about marketing as science.

The bottom line is that almost anything can work; its up to the individual to find what works well under his or her specific cultural conditions and watering habits.

[DavTom]

Thanks Ray, got it.

Well...now I have to use LECA! What specific product would you use if you were located in Europe? I mean if you know a good product that is easily available in Europe.

Dav

[Ray]

The product I imported and sold as “PrimeAgra” is Atami Hydro-Rokz.

[DavTom]

Thanks. Found it.

Dav

[DirtyCoconuts]

I like lava rock and Leca.

I use hydroton. I think it’s from Germany

[estación seca]

The only LECA I can find locally is Hydroton. It works, but I'm not fond of it. The particles are very regular spheres. They don't intercalate in the container. Other LECA I've used has irregular particles, which mechanically lock together in the container, making for a more stable root ball. Hydroton will move when picking up the container, and any particles spilled roll long distances on my concrete sunroom floor.

I was previously able to find other brands. But since marijuana use was legalized in my State, almost all the hydroponics shops have closed. The one nearest me only carries Hydroton.

[DavTom]

Sorry to bother Ray, it looks like that KelpMax and Quantum total are not easily available in Europe?

Do you know alternative products that can be bought in Europe?

Thx.

[DavTom]

thx

[Ray]

Can’t help with quantum, but KelpMax is the US name for Kelpak, which you should be able to purchase locally.

Y’all will get a chuckle out of this:

When I first discovered Kelpak and got samples (in 2010), I was so impressed with it that I thought other growers would be as well, so inquired about wholesale purchasing for resale, and was told I could not resell it. After a long negotiation, the producer relented, but only if I sold it under my own trade name - hence KelpMax.

In recent discussions about the availability of 1L bottles (instead of me having to repackage them), they commented that they would prefer if I sold it as Kelpak.

It appears that it will be less expensive for me to acquire the product in their 1L bottles than the current situation of me getting large jugs, buying bottles and labels and repackaging them myself, so once we get the supply chain set up (1st or 2nd quarter of next year, hopefully), I’m hoping to offer it at a lower price.