# Sodium toxic level for orchids



## DarioU (Nov 8, 2014)

I have read that for crops the toxic water level of Sodium (Na) is about 50-60 ppm. Is it tha same for orchids too? In an old article of Neptune, in "Orchids" AOS magazine, I remember that the adviced level of Na was below 10 ppm. What do you think about it?
Thank you


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## myxodex (Nov 8, 2014)

I do not have enough experience to give you a definitive answer but I guess that others here at ST will. I am also interested to hear what others think on this, but my guess is that it keeping below 10 ppm is a good idea.
I did look up literature on interaction between K and Na at the level of uptake in plants to see if there were some consistent basics, but it was more like different labs and different plants had different results. There does appear to be some interaction between Na and K at uptake but it is complex and not well defined. My guess is that your Na should be less than the level of K, so if you are feeding at 10 ppm K then your Na should be considerably less than this.

Some paph species have been found growing in colonies close to the sea (P. godefroyae, P niveum, and P.exul), all on limestone cliffs, but near enough to get periodic doses of sea spray. Given that these are high rainfall areas I suspect the regular flushing by rainwater keeps the Na concentration low enough. P. bullenianum has been reported growing on stumps in mangrove swamps !?

There has been some suggestion that Na be considered an essential element (although in trace quantities) but not sure this is generally accepted, except in the case of some halophytes.


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## Stone (Nov 9, 2014)

DarioU said:


> I have read that for crops the toxic water level of Sodium (Na) is about 50-60 ppm. Is it tha same for orchids too? In an old article of Neptune, in "Orchids" AOS magazine, I remember that the adviced level of Na was below 10 ppm. What do you think about it?
> Thank you



Where is the sodium coming from?


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## DarioU (Nov 9, 2014)

Irrigation water


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## Stone (Nov 10, 2014)

If it's NaCl in your water, the first to cause trouble will be the chloride. I don't know about the specific ppm that will damage the orchid. But if your total EC is below 0.5 dS/m I don't think it will be a major problem. If the EC is higher, you will need to know exactly what ions are in the water and go from there.

Water quality guidelines in one of my books says:

Effect on plant growth:
Chloride...greater than 140ppm=increasing problems
(you can probably halve that for Paphs)
Sodium (overhead watering)....greater than 70ppm=increasing problems
Chloride (overhead)........Greater than 100ppm=increasing problems
(you can probably halve these figures for Paphs)
Bicarbonate 90-520ppm...increasing problems. Greater than 520...unsuitible.


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## troy (Nov 10, 2014)

Would you use crystal geyser water to flush with?


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## gonewild (Nov 10, 2014)

Seedlings are more sensitive to Sodium than adult plants.
If your water has more than 15ppm of Sodium you should be concerned.
Best water has 0ppm sodium.


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## Ray (Nov 10, 2014)

troy said:


> Would you use crystal geyser water to flush with?




I assume that "Crystal Geyser water" is spring water, which can sometimes be higher in TDS than the local tap water supply. Without knowing more about the water, it's hard to say if that's a viable alternative.

You can probably Google its analysis.


Ray Barkalow
firstrays.com


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## DarioU (Nov 10, 2014)

It is very interesting that there are so different opinions about Na level in irrigation water: Below 75 ppm, the best would be 0 ppm........
Perhaps a good idea is that of Myxodex ?


myxodex said:


> ..... but my guess is that it keeping below 10 ppm is a good idea....


In deciding the right level of K is important the NH4+ level anda Na level too?


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## Ryan Young (Nov 10, 2014)

The addition of Humic acid will provide a buffer to excess sodium. I believe there are a few papers on it. 

Sent from my oneplus one


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## RNCollins (Nov 11, 2014)

gonewild said:


> Seedlings are more sensitive to Sodium than adult plants.
> If your water has more than 15ppm of Sodium you should be concerned.
> Best water has 0ppm sodium.



Our water runs through a NaCl Water Softener. Out of the tap it is 165 ppm. I now use RO water, but I used to get Phals to bloom with this water.


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## gonewild (Nov 11, 2014)

RNCollins said:


> Our water runs through a NaCl Water Softener. Out of the tap it is 165 ppm. I now use RO water, but I used to get Phals to bloom with this water.



But not 165 ppm of sodium?


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## RNCollins (Nov 11, 2014)

gonewild said:


> But not 165 ppm of sodium?



My TDS meter measures in ppm, but of what I don't know. I think the water softener takes out the iron in our well water, then exchanges it with salt...


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## Rick (Nov 16, 2014)

Ryan Young said:


> The addition of Humic acid will provide a buffer to excess sodium. I believe there are a few papers on it.
> 
> Sent from my oneplus one



This is a very interesting observation Ryan.

I do aquatic toxicity work on salt constituents and have also noted that the inherent toxicity (to aquatic organisms) of a TDS mixture is reduced with humic acid.


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## Rick (Nov 16, 2014)

From looking at surface and ground water quality from all around the world you would be hard pressed to find water that has more K than Na. K in the environment is very rare compared to Na.

There's a lot of research easy to find on the internet for drought capabilities and salt tolerance of crops like rice and cotton so if you are looking for extremes to avoid that's an easy source of data to find.

Also as Myodex pointed out there are several Paph species that grow in close proximity to the ocean.

Given that the spray and waves are constant and rainfall periodic I don't think that the heavy rain factor is what's saving these plants from NaCl toxicity.

Seawater is 30,000mg/L sodium chloride
It also has about 1000ppm Mg, 500ppm Ca, and ~400ppm K.

The balance of these materials is critical to salt water organisms.

I have done experiments with salt water fish and shrimp.
If you put them in a solution of 30,000 ppm NaCl with no Mg, Ca, and K, they will die in less than 48 hours.

If you add the appropriate amounts of Mg/Ca/K they do just fine (and you must add all 3 and not any of 2).

So if you just do part 1 of the experiment you would conclude that the toxicity of NaCl is <30,000 ppm, but if you add the Mg/Ca/K for part 2 you can actually get the NaCl concentration up to almost 60,000 ppm before they start to die again.


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## Rick (Nov 16, 2014)

DarioU said:


> It is very interesting that there are so different opinions about Na level in irrigation water: Below 75 ppm, the best would be 0 ppm........
> Perhaps a good idea is that of Myxodex ?
> 
> In deciding the right level of K is important the NH4+ level anda Na level too?



As well as Mg and Ca.:wink:

All of the above cations wrestle with each other and Ca and Mg are generally found at higher concentration naturally than NH4 and K


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## Rick (Nov 16, 2014)

I have done experiments with salt water fish and shrimp.
If you put them in a solution of 30,000 ppm NaCl with no Mg, Ca, and K, they will die in less than 48 hours.

If you add the appropriate amounts of Mg/Ca/K they do just fine (and you must add all 3 and not any of 2).

So if you just do part 1 of the experiment you would conclude that the toxicity of NaCl is <30,000 ppm, but if you add the Mg/Ca/K for part 2 you can actually get the NaCl concentration up to almost 60,000 ppm before they start to die again.


Although all the above is for fish/shrimp that I test in the lab, I believe this is the same as for those brachy species that Myodex is referring to.

There are a lot of culture references for brachies stating that they require low/no salts in their irrigation water and potting mixes. But in the environment they are exposed to very high TDS. However they are not exposed to conditions where the prevalent salt is potassium nitrate in a fertilizer mix. :wink:


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## myxodex (Nov 17, 2014)

Rick, you raise some important points. I remember the discussions on the rain fall data and that the Na was often higher than the K. Moreover Roth's leaf analysis showed higher than expected Na content. Wouldn't it be ironic if a small amount of Na turned out to be beneficial.


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## DavidCampen (Nov 17, 2014)

NaCl is a component that I add to my fertilize concentrates. I can't remember at the moment the ratio of NaCl to the other trace elements; it is probably around the same level as molybdate.


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## Stone (Nov 17, 2014)

myxodex said:


> Rick, you raise some important points. I remember the discussions on the rain fall data and that the Na was often higher than the K. Moreover Roth's leaf analysis showed higher than expected Na content. Wouldn't it be ironic if a small amount of Na turned out to be beneficial.



The trouble with the leaf data is that we don't have the subsrate and/or water data to compare with it. It is one thing to know what the plant is taking up but we really need to know what is available to it as those two sets of data may be different. Then we could have a better understanding of the plant's ecology.


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## Rick (Nov 17, 2014)

Stone said:


> The trouble with the leaf data is that we don't have the subsrate and/or water data to compare with it. It is one thing to know what the plant is taking up but we really need to know what is available to it as those two sets of data may be different. Then we could have a better understanding of the plant's ecology.



I think ST should fund an expedition to send you up to Krabi to collect tissue samples Mike.

I do think its funny that Na is so neglected in the hort. literature. Maybe its so ubiquitous in irrigation waters that nobody cares any more.

I see water reports from all around the world and its pretty rare to not see at least a few ppm of NaCl in surface and well waters. In lots of farming regions I see pretty high NaCl in surface waters compared to what we'd ever consider safe for orchids.

I can't recall which leaf litter data I was looking at a ways back and saw a fair amount of Na in it.


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## Stone (Nov 18, 2014)

Rick said:


> > I think ST should fund an expedition to send you up to Krabi to collect tissue samples Mike.
> 
> 
> 
> I agree. With a stopover in PNG and Philippines and Vietnam. $70,000 or 80,000 US should just about cover it. Come to think of it, there's the guides, car rental, pay-offs and bribes, tips.......Better make it an even 100.


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## gonewild (Nov 18, 2014)

Rick said:


> I do think its funny that Na is so neglected in the hort. literature. Maybe its so ubiquitous in irrigation waters that nobody cares any more.



Sodium has never been neglected in hort. It has always been considered as a serious problem. Just goes to show that science doesn't really know reality!


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