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Dec 16, 2009
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How about chloride? Bed of the life are the oceans, full of chloride. Either exoplasmatic or endoplasmatic space, chloride is essential. How we can give enough chloride for plants?
If you are fertilizing, particularly with chlorinated tap water or well water, I doubt there is any deficiency. Even from rain, you can expect 10-35 lb/A of Chloride ion deposition. So using rain water would provide Chloride and certainly our epiphytic orchids would get plenty in nature.

Now for some math. Data for the great plains is about 1 g/m2 max and, I guess, about 30 inches of rain. So, over 1 A with 30 inches of rain you would get about 814,620 gallons, so about 0.0002 oz/gallon (1.4 mg/L). Your average fertilizer should have more than that in it, having snuck in with micronutrients or chemical impurities. (Note: fertilizer manufactures avoid adding chloride due to salt toxicity fears so they aim to be as deficient in chloride as possible!) If you want to be sure I would guess add knife-tip of table salt or no-salt salt (KCl) to the mix. MgCl2 or CaCl2 might be a better option. Adding a tablespoon of bleach to the water is a good idea -- and will have the bonus of killing off surface pathogens. I am not aware of any optimal chloride fertilization studies. All I know is that some is needed but too much is toxic. There is some evidence to suggest that plants respond to chloride fertilization with better growth up to a point. Flowers are quite rich in Cl- ions so perhaps you could get better blooming?

Experiment and lets know what you find out.
The question, to me, is "what constitutes 'enough'?"
I wonder about plants grown in clear hydroponic system, where there is no any available minerals in the soil for plants. Conventional fertilizers don t contain chloride, rain water does not, too, chlor in the tap water is not Cl- but toxic Cl free atoms, if any, there are many place where peroxid is used for sterilization for tap water instead of Cl2 gas.
I have phrags that have been grown in passive hydroponic culture, using RO and no chlorine-containing nutrients, for decades, and have had no issues.

I'm sure there are plants that need a lot of chlorine and some that aren't nearly as demanding, but that might be said for pretty much any elements, I suppose.
The chlorine used to chlorinated drinking water is sodium or calcium hypochloride. Some will indeed dissipate as chlorine gas but a lot, because it is so reactive, will become chloride ions.

Rain water does have chloride. This is the point of one of the articles I cited and why farmers tried KCl fertilization.

As a scientist I cannot, for example, buy 100% KNO3. The best I can get is ultra pure which like 99.997% pure. I expect chloride salts make up the bulk of impurities. It is hard to get rid of. I expect there are chloride traces in all fertilizers. Further more, unless you use distilled water to dissolve the fertilizers some chloride will come in via the RO water etc... On Monday I cannshow you the salt stain on a glass beaker I filled with RO water and let evaporate dry. The harder your tap water the more salt contaminant will be in the RO.

I don't expect our plants have a chloride deficiency. The question is if a little more will so them good. Chloride seems important for flower and seed development. As a counter ion it is needed to move positive ions about in tissues and in so doing move water.