Mag. Nitrate vs Mag. Sulfate

[maitaman]

To the original question, if you use a nitrate you have to modify your fertilizer. Mg and S are minors, both of which most orchids like in moderation.

[Brooke]

Orchids3, I have no idea what you described to your friend, but this is high school chemistry. There are no reactions involved. Its just pure solubility of salts, nothing complicated. These are just ionic compounds who don't care what they associate themselves with as long as its the opposite charge.

Maitaman, I think you misunderstood. This is just a wash for the clay before you use it. It is not something that you do repeatedly. No fertilizer changes required, this is just a preliminary cleaning of the clay.

Ray, I'd have to see that data. Makes no sense to me. Just can't be right. I can see the additives having no effect whatever, but not enhancing the contaminants removal.

[Ray]

Brooke,

I'm a materials engineer myself, so I fully understand the cynicism!

It seems to me that in a water-softening environment, the sodium chloride driving the others out makes sense, but there is no logic that says that sodium salts will have more solubility in a mineral-laden water than in a somewhat purer one.

[razka3]

So I had my GF ask her chemistry professor what she thinks about this. She ends up being an avid gardener as well. She says people often add CaNO3 & MgSO4 (which forms gypsum) to soil that has a lot of clay in it to "soften" the clay - whatever that means. She also says the NaCl would easily wash out with just water, there would be no chemical reaction needed.

Just a hypothesis - but what if there could be a reaction between the CaNO3 & MgSO4 & NaCl that would leave behind just the Ca and Mg, with the rest bonding with the NaCl and being flushed out with the water? That would be the only viable solution I could see that would go along with the study Ray has seen. However I don't know enough about chemistry to say either way.

This has gotten me quite curious though!

[Magnus A]

One more hypothesis

If the material that is washed (LECA in this case) has alot of micropores with Nacl in them. The gypsum formed from Ca and sulfate could block the pores so the NaCl is trapt in the material. This should also explain why you need several washes to get rid of the NaCl without the extra salt.

/Magnus

[goodgollymissmolly]

"....but what if there could be a reaction between the CaNO3 & MgSO4 & NaCl that would leave behind just the Ca and Mg, with the rest bonding with the NaCl and being flushed out with the water..."

Look guys, this is a perfectly respectful answer, but I need to say something here. You can "what if" until Hades freezes over. This is not rocket science, it's simple chemistry. There is no such reaction (or reactions) as you postulate. If there were then the answer would be different. The science teacher/professor you quoted was right on. BTW, the reason that people add gypsum to clay soil is keep it from hardening into unworkable "concrete" when it gets dry. In my opinion it does not work very well, but some people like the results and it does no harm.

As for insoluble substances blocking pore structure and permanently trapping any internal NaCl contamination, that's possible. However, you would not want that to occur. The internal pore structure of the clay is a vital pathway for water to rise in the clay from the reservoir. The driving force is surface tension and the rise is called capillary action. It can occur on the clay surface as well if the surface is rough enough on just the right roughness levels, but the best capillaries are internal. You can even calculate the rate of rise if you assume some simple capillary geometry. Calculating the actual results will lead to you to some exotic mathematics however.

[razka3]

So, it seems as if there is definitely no benefit, since a vast majority of the CaNO3 & MgSO4 & NaCl would be washed out in the rinses because of their high water solubility.

Moral of the story - rinse with hot H20. Add CaNO3 & MgSO4 in minute quantities with fert feedings if needed. Thoroughly rinse LECA every 4 weeks with tepid H20.

[newflasker]

Come on guys. Why do you want to fight with each others? All of you are correct. I’m not kidding. You want to dissolve sodium salts in LECA right? Use water to dissolve them. Use hot water and vinegar will improve the process, simple chemistry. However, do you think you dissolve 100% sodium salts? Give me a break. This is the real world; it’s not in the pure chemistry lab. There are small amount of sodium salt traps in the structure and there’s no way that you can dissolve them unless you break the structure. There are some unknown or whatever chemicals in soil, CHC, LECA that work like sodium ion resin in the water filter purifier. Do you think you pour pure water in and dissolve sodium ion out? If it happens like that you waist $50 buck to buy water filter. No, you pour hard water which contain calcium ion in; ion calcium replaces/exchanges ion sodium and release sodium ion out and we have soft water. See below picture. You can add small amount of calcium nitrate and magnesium sulfate to release sodium in soil, clay, and CHC. This is no longer pure chemistry; this is soil engineering or whatever. So all of you are absolutely correct in each case. All of you are winners. Remember a brush may help a lot to elimate sodium, simple minded. Cheers

[maitaman]

That is the real secret. HOT water will dissolve a heck of a lot more salts than cool or room temperature water. even non-ionic compounds. Heat sugar in water and see how true that is. At McLellan's a few years ago we had the steam heating pipes running through the tanks to bring it almost to boiling. That also activates the sterilants in many cases.

[Ray]

While adding the Ca & Mg minerals may or may not accelerate the cleaning process, it will leave some useful minerals in the pellets.

As to the soil thing - soils have a lot of clay in them, and clays are plate-like in shape. Soil pH determines the relative electrical charges of the faces and edges. Under acidic conditions the "plates" stack face-to-face, which is dense. As you increase the pH, the edge charge changes, and there is a greater percentage of edge-to-face attraction, leading to a "card house" morphology, which is more open, softer, and more absorbent. Lime, dolomite, and gypsum all raise the pH, but vary greatly in their solubility.