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Benifits to using rain water?

This is a discussion on Benifits to using rain water? within the General Orchid Culture forums, part of the Orchid Culture category; TDS figures are more reliable and appropriate than electrical conductivity for two reasons.1) Electrical conductivity ...

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  1. #21
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    TDS figures are more reliable and appropriate than electrical conductivity for two reasons.1) Electrical conductivity measures the no. of ions, (charge carriers) both anions (negatively charged ions) and cations (+ ions), it cannot measure nonionised material in a solution, so you can have a solution with a very low EC value but very high TDS, this is especially a concern when we handle organic compounds. For eg if you dissolve 100 g sugar in 200 ml water the EC will give you no conductivity because sugar does not ionise, but the TDS will be high 2g/L enough, same is the case with urea. If you do not have organics and other non ionisable stuff then TDS correlates to electrical conductivity in an exact relation:

    TDS (ppm) = 0.64 X EC (μS/cm) = 640 X EC (dS/m)

    So actually it is the other way round, by knowing the TDS you can try evaluating the EC, but not the vice versa. Now 2) Eventhough it is the electrolytes that are acting as nutrients and the electrochemistry in the pot that is important, more important is the fundalmental of osmotic pressure. Plants are trying to accumulate ions etc against the natural gradient by using energy, now when you have high TDS the tables are turned, water will flow outside from inside the roots burning them in the process. Ever noticed that the green root tips on orchids turn black and brown on the slightest application of fertilizer? So you can easily kill an orchid with right EC water but the wrong TDS.

  2. #22
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    Ha Ha! Did you get all that Ali? I love it when deeply scientific orchid culture debates flare up! I just wish I could understand it better--I always feel like I have stumbled into a debate luncheon at MIT sponsored by the Electromagnetic Interactions Group and they have asked me to transcribe meeting minutes into ancient sanskrit. (Of course, by that I, in no way, mean to imply that Geoff and Amey are being nerdy.)

    It does make me wonder why I am so drawn to hobbies that make me feel stupid. But I suppose that is a matter for my psychoanalyst.

    I have not put a lot of effort into testing or understanding my tap water, mostly because my house had a Reverse Osmosis system installed for drinking water, so I use that for my orchids. It takes a while to get enough water for my expanding collection and I occasionally suffer guilt over the gallons of water that go down the drain in the RO process. But it seems to be working. My brother-in-law recently picked up a new RO system from a pawn shop. My sister is excited because I have been dragging her down with me into orchid addiction and their water is very hard.

    This house also has a rainwater cistern that collects from the rain gutters surrounding the entire roof. Unfortunately, the system for getting the water out is cumbersome and unwieldly. If my collection grows much larger, I will have to figure out an easier way to use it.

  3. #23
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    BTW there are two common misperceptions about watering, maybe they have been mentioned in this thread already, but I'd like to correct them;
    One - cold water. It is often said "use warm water" or "keep the water in the greenhouse so that it is at the same temperature as the plants".
    This is quite unnecessary. Just think about it ! In the wilds, the water has not been warmed up . It is ( almost always) much colder than the ground temperature. Even here in temperate zone England, when it rains the air temperature drops a few degrees C.- the actual water is much colder than that. Some orchids need that cold shower, perhaps an especially cold shower from a vigorous thunderstorm, in order to be shoicked into flowering ( e.g. the pigeon orchid of Malaya etc). No, warm water is just anthropomorphism. ( Don't go mad and use water which is actually freezing - that is not natural, either ).
    Second , chlorine. It's not harmful- in the dilution found in tap water; it is a mild disinfectant ( which is why it gets put into tap water). I wash my seedlings, when I break open a flask, under the running cold tap to cleanse them of the agar jelly and disinfect them before planting in the seedling tray or compot. The reason for not wanting to use tap water is nothing to do with chlorine, but because of the dissolved salts. Or of course if it is hard water, some kinds of hard water ( not all) leave a lime scale crust on plants which is unsightly and difficult to clean off when preparing a plant for showing. But when I lived in a limestone area of England ( the Cotswolds) I commonly used my tap water, without any added fertiliser, and grew very good orchids. On th other hand, before that I lived in another place, in an agricultural area, where the farmers poured nitrogenous fertiliser on the ground to grow their cabbages and onions, and the tap water came from bore-holes and it was sheer poison for orchids ; all of which goes to show that rain ( barring atmospheric pollution) or Reverse Osmosis water is good - it's got nothing in it, and you can put in what you want. Tap or ground water is so extremely variable that it could be magic or poison, andd you can't tell by looking at or even drinking it.

  4. #24
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    LOL, We are not NERDS we are intellectual overseers for the human race ROFL

    Sorry if we bored you lot, thats why we have taken the discussion to emails hehe

  5. #25
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    Thank you both for the in depth science of testing water I won't claim to understand it though! And thanks again Geoff for clarifying those two points, I've heard a lot of mixed things about both. My orchids seem to be doing just fine on carbon filtered water, but I think the water quality at work is actually better than the town I live in....which may be why they seem to do so much better there! I may try collecting some rain water and see how that does with my plants - even non-orchids. I think my houseplants could use something a little better haha!

  6. #26
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    I have enjoyed reading this post too. Always great to learn more. So glad you guys share so freely here with all of us.

    Cheers,
    BD

  7. #27
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    Thanks to the folks who contributed to this post. It's really useful for a novice like me. I have been using rain water for my orchids, but never understood why. I have a fiberglass rain barrel installed under a downspout. My rood is a polymer membrane, so I don't think it leaches anything into the water.

    I fertilize weakly weekly, but I don't often remember to flush out the medium. Most of the time there isn't much salt buildup at all. That reminds, me, I think I need to flush them out now that I've remembered.

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    Don't forget that most fertilisers are designed in the belief that they will be added to ground water from streams, rivers, wells, or tap water - and consequently miss out the Calcium and Magnesium needed when using rain water or RO water.

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    Thank you for adding that. I didn't think of it. I use a commercial bark mix that contains oyster shell calcium. I could add egg shell to the mix if it didn't. Rarely I run out of rain water and then I do use tap water. My house water is mineral laden, based on the crust that forms on my fixtures. The orchid growth is quite good, and they do bloom, so I think I'm doing OK. Lately I've been giving them a half teaspoon of magnesium sulfate / epson salts per gallon once monthly as a 'tonic' as well. All totally nonscientific. Thanks again, that's really useful to learn.

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