Sodium and chloride requirements.
 

In formulating a nutrient mixture for use with RO water, I wonder what levels of sodium and chloride should be used. I see that the Dynagro Orchid-Pro formulation has 0.1% of each. Does anyone have opinions as to how much sodium and chloride should be in a formulation for use with RO water?

Sodium isn't considered as a part of 17 essential elements of plants (version from around 1980s), is it? But it is a beneficial elements (defined as elements essential for only limited groups of plants or plants grown under certain environments).

Internal concentration of Chlorine in healthy plants is 100ppm of dry weight (Epstein 1972, Mineral Nutrition of plants: Priciples and perspectives). It's similar to Iron. But I don't know about the uptake efficiency etc.

Thanks, I am working on nutrient formulation for my own use. I will defintely add chlorine as KCl but there doesn't seem to be any need for sodium and there will always be trace amounts of sodium in all the other ingredients.

hello, i have a strange problem/ question. my orchid plants were recently infested with tiny snails, and these critters destroyed the tender roots and new shoots of almost all...i was devastated.... i tried all possible measures including pesticides and apple slices and stale beer... none worked...its too difficult to pick each one of these physically from the 75 odd plants i have! I tried spraying common salt powder and they just frothed and died immediately.... my question is, will it hurt my plants to have NACl exposure in this form sprinkled at the top of the media? pl help or suggest alternatives.

The problem with any salt, including fertilizer components and table salt or NaCl, is that the plant (or snail) has a certain concentration of dissolved salts in the tissues, and the roots (or snail skin) act as semi-permeable membranes. Applying a much high concentration of salts to the roots (or snail skin) results in salts going into the plant (or snail) so the concentration of salt approaches equilibrium across the semi-permeable membrane, and the plant (or snail) can die from having too high a concentration of dissolved salts in the tissues.

So I would wash off the salt from your plants with pure water as soon as I thought all the snails were fatally injured. I don't know how long it takes to damage orchid roots with salt but I suspect it isn't long.

We don't have snails like that in North America. I might suggest asking other gardeners where you live how they deal with this problem.

I agree NaCl isn't a smart option. It depends on the concentration, but if it is killing snails instantly, it is probably really bad for plants, too. But please let us know if you get the snails back in a couple months or not. They are pretty tough to eradicate.

I think you are talking about Bush Snail (Hawaii Orchid Snail). DavidCampen had tried several methods to control them. I'm also trying some. It is extremely hard to get rid of them.

There is a scientific paper showing 2% Caffeine is highly effective. But as David and I found out, it is not a good idea. Caffeine is phytotoxic, and it interfere with root growth. After application of 2% caffeine, all green tips disappeared within a couple days. Then it took more than 2 months to restart the growth. Phalaenopsis seems to be more sensitive than Cattleya, Dendrobium, Paphs, Phrags. I lost quite a lot of Phals during this process. It seems fairly effective, but the snail did come back eventually (since I didn't want to apply it again). I have tried Physan-20 at the recommended rate. As David mentioned, this does seem to kill snails, and the phytotoxicity is generally mild for orchids. But I couldn't completely eradicate. Then there is Deadline.
Deadline 32 oz. Slug and Snail Liquid Killer-100509275 - The Home Depot
It is not meant to be for spraying, but the scientific paper showed some effectiveness. I tried 2TBS/gallon, and bush snails don't like it. But again, it eventually comes back. The most effective is Mesurol, but you need a pesticide applicator's certificate to legally obtain it. It is a neuro-toxin to human, so you need to be a bit more careful.

Most "bait" type snail poison doesn't seem to work. Probably the best method is repot all of them and make sure no snail is hiding in the pot.

According to Benzing in "Vascular Epiphytes", "all C4 and CAM taxa require sodium".

But the amount of salt required to kill snails would almost certainly badly damage your plants.

I've also read additional info about Na more recently in Marschner's Mineral Nutrition of Higher Plants. With regard to the essentiality, here is what Marschner's book say: "..., the conclusion by Brownell and Crossland (1972) and Brownell (1979), that Na is essential for all higher plant species with the C4 pathway, is not correct." This is based on later studies of maize and sugar cane (both C4), which doesn't show any increase in growth by Na addition. It appears the actual mechanism of why additional Na helps C4 is not completely understood, but it was suggested that Na is used to transport Pyruvate (used to store and move around CO2 in the C4 pathway). But it appears that some C4 plants like Maize use slightly different mechanisms to transport pyruvate. So "all" part of Benzing may not be strictly correct, but it appears that addition of Na in the orchid nutrition (at the micro-nutrient level) might be a good idea for CAM plants.

David, did you win the fight against bush snails? I'm reaching to the similar conclusion as you that Mesurol might be the only way...

FWIW, for years I sprayed my greenhouse monthly with one ounce per gallon (5.25% sodium hypochlorite) chlorine bleach as a general disinfectant/algaecide, and never saw any damage.

I am not a big fan of Benzing's writing style. I find a lot of his statements to be ambiguous and without references. I will have to get a copy of the other book you mentioned.

I have been using NaCl in my fertilizer formulations to give 1 ppm of NaCl in the ready-to-apply solution. That was my only source of chloride as well as sodium but I noticed a bit of interveinal chlorosis in some of my thin leaved orchids and began worrying that that was not enough chloride so I have increased the chloride to about 5 ppm in the ready-to-apply solution by adding KCl to the formulation.

I have given up for the time being.

I want to get some Bayluscide or equivalent; it is effective in very low concentrations. In Thailand and other SE Asian countries it is sold under a different name for treating for intestinal parasites in humans. In the U.S., if you have an applicators license, you can buy it in large quantities for dumping into lakes.