Fertilizer dilemma

[Roberta]

Originally Posted by GoldStar135

Hello again-
Is there a max amount of TDS that an orchid can tolerate reasonably? Around 200-300ppm?

My current fert solution consists of around 63 tbsp in a gallon can mixed with RO water (around 143ppm). With about half a teaspoon of fert the TDS showed up at around 171ppm. Would that be okay to apply to my plants? I watered one phal with the solution yesterday and today it seems normal (aside from a few small brown marks on the newest roots).

I did mix up a solution with about a cup of well water+RO water-it measured around 48ppm (close enough to 1/16 of 600ppm(37.5)). I'm just a little paranoid about the pH situation and felt that it wasn't enough well water mixed in with the RO water.

Thanks in advance

For what it is worth, I have been growing most orchids successfully with southern California tap water that ranges from a low of 250 ppm TDS to maybe 400 or so, average is around 300-350 most of the year. Plenty of other local hobbyists who live in nearby cities are well above that (500-600)and get away with it on a variety of orchids (Phals, Cymbidiums, and most Cattleya-type hybrids seem not to care much. Many Pleurothallids, Sophronitis species, etc are much more sensitive... grow what grows easily). Our TDS is mostly calcium carbonate - if it were sodium instead of calcium it would be pretty deadly at that level, calcium salts aren't all that soluble so they aren't very harmful either. Those numbers are before fertilizer, which I use once a week or every two weeks (whatever I get around to it) at about 1/2 teaspoon per gallon or less. Fertilizer is the least important element of culture... think of it as vitamins rather than "food"... vitamins won't make a sick person healthy. No matter what your starting point is, 1/2 teaspoon or even just 1/4 teaspoon (dry) per gallon of fertilizer at most once a week is plenty.

[estación seca]

RO and DI don't extract nutrients from the body. They fail to supply the nutrients we need on an ongoing basis. We lose calcium in small amounts constantly, and almost all calcium we take in comes from water (drinking and cooking.) If the water we drink lacks calcium we don't get the calcium we need. It is not a good idea to drink RO or distilled water, on a regular basis, instead of water with normal levels of minerals.

Even very high levels of calcium in water are not a problem for humans. Our uptake of calcium is regulated mainly by the amount of vitamin D we have. When there is a lot of calcium in our water, we take in some, and the rest goes through our gut, bound to bile acids and not absorbed. It would be nearly impossible for most people without vitamin D excess to get too much calcium from water, since it is so insoluble.

[Roberta]

I was just pointing out that a lot of orchids really don't care all that much about TDS if it's due to calcium. Sodium is the bad actor (some orchids have evolved in areas that get ocean spray, but not many) People can get the calcium they need in various ways (if you don't like water that tastes like chalk, drink milk...)

[estación seca]

Only a very small fraction of the world's adults can tolerate lactose, those with ancestors from northern Europe. Water is it for calcium intake.

[Arizona Jeanie]

(Apologies, GoldStar, for a little detour here.)
Regarding the statement that we get most of our calcium from drinking water:
My recommended daily calcium intake is 1200 mg/day.
I get about 400 mg/day from food (estimated).
My drinking water has about 120 ppm calcium carbonate (=7 grains/gallon) per my water company.
How much tap water do I need to drink daily to make up that other 800 mg/day of calcium? I'd like to give up those chalky supplements.
My math skills are very rusty , can anyone help me on this calculation? Thanks.

[estación seca]

1 grain is about 65 milligrams.

7 grains contain about 453 milligrams.

Various foods you eat may bind calcium and make it unavailable.

You cannot absorb calcium without adequate vitamin D levels. Cholesterol is converted to vitamin D in human skin by sunlight. Wearing clothing or sunscreen prevents this. Many people are vitamin D deficient, and supplementation is often necessary.

Lack of skin pigmentation probably evolved during the migration to northern European and Asia, as a response to decreased light in the long winters, and the necessity of wearing heavy clothing, leading to vitamin D deficiency. Those with less pigmentation were able to make more vitamin D.

Vitamin D deficiency at high latitudes probably also explains why northern European populations changed to tolerate lactose after childhood. Most humans are unable to tolerate lactose after weaning. Milk products are the best source of dietary calcium. It would be a great advantage in a northern climate with poor vitamin D production to be able to take in calcium via dairy products.

This shows foods high in calcium:
Calcium content of common foods | International Osteoporosis Foundation
Note that sardines are considered high in calcium because we eat the bones.

It is difficult for both men and women to get enough calcium without supplementation while eating a typical US diet. We were designed to wear out as the first few kids reached reproductive age.

[Ray]

Another way to look at it:

120 ppm is 120 mg/kg. A kilogram of water is about 1.06 quarts, so you'd need to drink about 5 quarts to make up 600 mg.

[Arizona Jeanie]

OK, if I'm figuring right, to get my 800 mg of calcium from my "moderately hard" tap water, I'd have to drink about 14 pints a day (1.76 gallons, 6.67 liters). Somehow, I don't think that's going to work on a daily basis. Besides, my tap water also has a bit of arsenic, 9.3 ppb. Anyhow, the idea of humans getting all their calcium from tap water wouldn't work too well here. I'm glad the orchids seem to be OK with it.
Those of you with your own wells--I'd strongly recommend getting at least one complete water analysis, there can be some surprises in there besides the calcium.
Estacion--when I lived in the low desert, one of the jokes was: you've lived in the desert too long when you go to the mountains and the water tastes funny. I live in the mountains now, and the water does taste funny. Might be that arsenic...

[Dollythehun]

Arizona Jeanie...you'll just have to suck it up and start taking those calcium horse pills the Dr suggested. 😁😂🤣😃 Idk about water but, you'll probably never get enough intake otherwise and at my age I hear it's super important ( that doesn't make it less inconvenient). We live a couple of miles from a closed landfill, so we tested and although it was ok (then) we filter the heck out of it.

[Arizona Jeanie]

Oh Dolly, in my heart and bones, I know that you're right about those calcium pills! I can't drink enough of our hard water, and there's something about crunching up those little sardine bones that I find unappetizing.
Thanks ya'll!