# Thoughts on sulphur?



## Stone (May 7, 2015)

Given that the loss of Sulphate-S from containers is in direct proportion to the amount of water leaving the pot (sulphate being an anion), I think it is safe to assume that in some cases the leaching of S from pots may be too much unless there is a continuous supply.

Also, considering that many plants use as much S as they do Phosphorus I believe that some ferts are not providing enough.
I wonder if the greening of plants sprayed with Mg sulphate are showing a response to the S as much as the Mg in many cases. Remembering that the Mg is held much more in the media than the S.

If we are using very pure water and water a lot, perhaps we need to consider supplementing S in some way.
I have gone back to adding a sprinkling of crushed rock gypsum to the top of pots as well as a little (as fine powder) to the irrigation water.
I am pretty sure I have observed some greening.

It is suggested that S should be around 1/8 of the N. 95% of the SO4 in the soil comes from decomposed organic material (the kind of stuff Paph roots grow in)

Has anyone else considered this?


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## naoki (May 7, 2015)

Tim (myxodex) made a very interesting point about the similar topic last year:

http://www.slippertalk.com/forum/showthread.php?t=35172

It appears that atomospheric SO2 can contribute somewhat. But precipitation of Ca SO4 could be an additional cause of S deficiency.


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## Stone (May 7, 2015)

Thanks naoki. I should have searched
However the point remains relevent! It seems S is often easily forgotten. There is very little S in the water or the air down here. (at least insufficient)


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## naoki (May 7, 2015)

After Tim's point, I read a bit about S deficiency. "Generally" S deficiency should show up in the relatively new tissues since the phloem mobility of S is intermediate.

http://www.ces.ncsu.edu/plymouth/cropsci/docs/sulfur.html
http://plantscience.psu.edu/researc...itional-disorders-displayed/sulfur-deficiency

After I saw the results of a nutrient deficiency experiment of my students (with sunflowers), I re-confirmed that those "typical" deficiency symptoms quoted to some crop plants are not general to all species. So we shouldn't be stuck with what people say about corns or tomatoes. I wish we could do the same kind of deficiency experiments with Paphs!

There were several opinions about the chlorosis I observed in this thread:
http://www.slippertalk.com/forum/showthread.php?t=36454
But I still think that S deficiency (via Ca So4 precipitation in the stock solution) is the most likely cause in this case. The plant is completely recovered now. I'm (stupidly) still using the heavily precipitated MSU with MgSO4 addition (for some plants), and I haven't seen another victim yet....

If I'm right about this (i.e., S is relatively immobile in orchids), then greening up of the whole-plant chlorosis by epsom might not be due to S deficiency. But this is a pure speculation, and good to hear what others think about it!

I might be wrong, but didn't Rick say that he is supplementing K-lite with MgSO4 recently?

So is there advantage to use not-so-soluble Gypsum over Epsom, Mike? Is it like a slow-release fertilizer?


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## Bjorn (May 7, 2015)

I am currently feeding With my home-made mix at approx 60ppm TDS. Below, the composition is given in ppm

ppm
N total	10,136
NH4	6,399
NO3	3,737
P	0,948
K	1,580

Ca	3,442
Mg	1,157

Fe	0,057
Mn	0,343
Zn	0,192
Cu	0,161
B	0,111
Mo	0,056
Co	0,007
Ni	0,009
Na	0,027
Cl	0,011
S	7,897
You might notice that there is only 10ppm N, no urea but 2/3rds of it as ammonium, and an almost equal amount of sulphur (as sulphate). Additional is citric acid to regulate pH and to complex.
Occasionally (once a month) I also add kelp and recently started an addition of 50ppm fulvic acid with the fertiliser.
Although the addition is tiny, so far I have not seen any signs of deficiency, actually a few of my plants have shown quite an improvement after turning into this feeding regime. The leaf-colors are nice grass-green, not very dark and not yellow, just green. I pay a particular attention to the leaf-sizes, the last leaf should never get smaller. Seems to work out fine so far, most new leaves are significantly bigger than the previous.
What is obscuring the total picture somewhat and potentially be the reason for the good growth, is tha water I use. Its coming from a bog and has a conductivity of some 150 microsiemens, which should transform to some 100ppmTDS if I remember rightly. Some of it is probably humic substances, there is no alkalinity nor Ca or Mg or nitrate. I simply do not know whats in it. Guess its low in nutrients though.
I firmly believe that the slippers do not need more nutrients than I give them and that my proportions in the micro-range is closer to their needs than what is commonly offered. If you look at the proportions in the micros, (below) my Fe:Mn:Zn is 1:6:3, more common is 3:2:2 (K-Lite)
Fe/X
Fe	1,00
Mn	6,07
Zn	3,39
Cu	2,85
B	1,96
Mo	0,99
Co	0,13
Ni	0,15
Na	0,47
Cl	0,19
There is much more of the micros as well, in my mix there is e.g. 0.57% Mn, below 0.1% is common in other fertilisers (K-Lite has 0,08%Mn) All micros are twice to four times higher than common. The reason is of course to have them available at the very low fertiliser levels I am using.
Results? so far so good, after three months of application, and before that three months of no fertiliser, I have not seen any new symproms of deficiency. Some of the plants have shown , I would phrase it shockingly, good growth, a few leaves being not bigger than their predecessors, but that is it. My canhiis are prospering, my kovachiis seem to thrive, marginal decease incidents only etc.
Is it due to the feeding regime? I do not know, still too early to judge long term effects but so far its good.


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## Stone (May 7, 2015)

naoki said:


> > So is there advantage to use not-so-soluble Gypsum over Epsom, Mike? Is it like a slow-release fertilizer?
> 
> 
> 
> ...


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## Stone (May 7, 2015)

Bjorn said:


> I am currently feeding With my home-made mix at approx 60ppm TDS. Below, the composition is given in ppm
> 
> ppm
> N total	10,136
> ...



Not a bad mix Bjorn (your K is too WAY too low for my liking though)
So what is the EC of your final watering mix?


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## Bjorn (May 7, 2015)

Stone said:


> Not a bad mix Bjorn (your K is too WAY too low for my liking though)
> So what is the EC of your final watering mix?



Varying a bit but approximately 250µS as far as I remember. The addition is 1:160 using 0,5% solution twice (one stock without Mg and Ca and one with) using two proportioners. Should give approximately 60ppm into the water. The K is kind of compromise


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## Ray (May 7, 2015)

Stone said:


> Also, considering that many plants use as much S as they do Phosphorus I believe that some ferts are not providing enough.
> I wonder if the greening of plants sprayed with Mg sulphate are showing a response to the S as much as the Mg in many cases. Remembering that the Mg is held much more in the media than the S.
> 
> If we are using very pure water and water a lot, perhaps we need to consider supplementing S in some way.



I agree with Naoki's assessment that we can't read too much into studies done with other plants, so we really don't know if that first statement quoted is even pertinent.

Also, S demand varies all over the map, and as it plays a key role in protein synthesis in plants, it makes sense that slow-growing plants, like orchids, probably don't need as much as fast-growing plants.

I use pure water (RO @ <10 ppm TDS), flood the plants at least 3x/week, but have 25 ppm N K-Lite in it at every watering. K-Lite is 0.1% S or roughly 10% of the level of P, and at 3.5 years into that feeding regimen, I see no indications of any deficiencies. They're not getting a lot of anything, but they get a little, and get it often.


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## gonewild (May 7, 2015)

Stone said:


> However I water very heavily (with rainwater mainly) when I do and I suppose one ''advatage'' is that with the use of solid CaSO4 there is always a certain imput of Ca and S. Gypsum is some 10 times more soluble than limestone so you can use quite large particle sizes (up to 3mm). All of the gypsum samples I have tried have a small percenatge of Carbonate in them as well (going by pH)
> I also use my organic fertilizer as my main source of nutrients and there is good S levels in that as well.



Adding gypsum to the media supply S seems like it kind of defeats the value of pure water. The advantage of having pure water (rainwater or RO) is that it has no nutrients in it. This gives you the opportunity to add to the water exact amounts of any nutrient you want o supply and you know what the amount is. When you add solid materials that slow release nutrients to the substrate you have no idea how much will dissolve with each watering so you have no idea what nutrients are actually available to the plant.

Sulfur should always be available for the plants so it should be included in the nutrient list of the fertilizer being used. There does not seem to be a problem with over supplying S so I always use MgSO4 and it seems to provide enough so that I've never had an S deficiency.

In reality there probably is enough S leaching from the bark and organic matter in the media or coming from the atmosphere that keeps the plant supplied without adding S to the water.


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## Stone (May 7, 2015)

Ray said:


> > Also, S demand varies all over the map, and as it plays a key role in protein synthesis in plants, it makes sense that slow-growing plants, like orchids, probably don't need as much as fast-growing plants.
> 
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> ...


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## Stone (May 7, 2015)

gonewild said:


> > Adding gypsum to the media supply S seems like it kind of defeats the value of pure water. The advantage of having pure water (rainwater or RO) is that it has no nutrients in it.
> 
> 
> 
> ...


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## gonewild (May 7, 2015)

Stone said:


> So if we accept that all plants require between 1/8 and 1/10 S of their N, a feed should also contain these types of ratios.
> 
> Therefore I would suggest that the S in k-lite is nowhere near enough and your plants are either getting enough from the kelp you use or are deficient in S whether it is visually obvious or not. Symptoms may not be apparent unless there is a severe deficiency.



Or you were wrong in assuming all plants require 1/8 - 1/10 S of their N.
Or orchids extract S from the media. Pine bark has about 2ppm S content that would add to the S supplied in the fertilizer solution.


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## gonewild (May 7, 2015)

Stone said:


> That's where you're wrong. S is depleted within weeks from a bark medium without more constantly coming in.



Within weeks is pretty fast. Is that fact or assumption?


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## gonewild (May 7, 2015)

I was incorrect pine bark has a higher sulphur content than I wrote above.

Pine bark composition ppm:

NO3-N (ppm) 0.1
NH4-N (ppm) 0.1
P (ppm) 4.0
K (ppm) 52.5
Ca (ppm) 16.2
Mg (ppm) 11.5
SO4 (ppm)50.9


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## Stone (May 7, 2015)

gonewild said:


> Within weeks is pretty fast. Is that fact or assumption?



Fact


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## Stone (May 7, 2015)

gonewild said:


> I was incorrect pine bark has a higher sulphur content than I wrote above.
> 
> Pine bark composition ppm:
> 
> ...



You are only going to see a tiny fraction of that from the SURFACE of the bark as it breaks down over time. Not nearly enough for any plant Lance.


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## gonewild (May 7, 2015)

Stone said:


> Fact



Can you please share the documentation for the fact.


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## Stone (May 7, 2015)

gonewild said:


> Can you please share the documentation for the fact.



Man why can't you just take my word for it for once!oke:


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## gonewild (May 7, 2015)

Stone said:


> You are only going to see a tiny fraction of that from the SURFACE of the bark as it breaks down over time. Not nearly enough for any plant Lance.



Mike in your previous arguments about sources for plant nutrients you insisted that most nutrients come from decaying plant matter. Now you have reversed your thinking?


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## gonewild (May 7, 2015)

Stone said:


> Man why can't you just take my word for it for once!oke:



If I believed it was true I would take your word for it. :evil:
I'd like to know how all the sulfur leaches out of bark in a few weeks time and also when does the time start....when the tree is cut or when it gets put into a pot? Come on show the proof!

Personally I know that a good supply of S is a benefit to the plant but since you started the thread and have said Rays plants are deficient of S even though they show no symptoms then you need to support that with proof of some sort.
We can't just leave this for people to think they need to add more S if in fact they don't.


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## Stone (May 7, 2015)

gonewild said:


> Mike in your previous arguments about sources for plant nutrients you insisted that most nutrients come from decaying plant matter. Now you have reversed your thinking?



Actually no I don't think I said that in relation to orchids in the habitat. Most nutrients for epiphytes (apart from N) comes from rain and canopy leaching.
Most soil S does come from organic matter but it would be from decomosed leaves, moss, lichen, fungi, humus etc. All of which have an enormous surface area. But not big chunks of pine bark.


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## gonewild (May 7, 2015)

Stone said:


> Actually no I don't think I said that in relation to orchids in the habitat. Most nutrients for epiphytes (apart from N) comes from rain and canopy leaching.
> Most soil S does come from organic matter but it would be from decomosed leaves, moss, lichen, fungi, humus etc. All of which have an enormous surface area. But not big chunks of pine bark.



I assume we are not talking about soil. Chunks of pine bark leaching would be somewhat similar to canopy leaching from rainfall.
Pine bark is only an example of many organic components of orchid growing media and it is not just big chunks in a pot. 

I think you think I'm arguing against your idea that plants need more S than normally supplied in fertilizer? I'm not.
What I am suggesting is that they get a certain amount from the substrate media and what is normally in fertilizer is enough to make up the difference.


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## gonewild (May 7, 2015)

Here...
http://www.isaet.org/images/extraimages/B114003.pdf

Indicates N/S ratio is optimum at 15:1 for invitro seedlings.
That is much higher than K-lite has that Ray mentioned he is using.
But it also does not take into account the long term growth effect of elevated S. Rays observation does take into account long term growth.


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## Stone (May 7, 2015)

gonewild said:


> .
> 
> 
> > Chunks of pine bark leaching would be somewhat similar to canopy leaching from rainfall.
> ...


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## Ray (May 8, 2015)

I'll drop in a couple of points here.

1) None of us actually knows what a plant requires. It's all conjecture based upon incomplete data, and that data is particularly sparse when it comes to orchids.

2) I don't think we should underestimate the array of chemicals exuded by the forest canopy-producing vegetation. Most minerals are, indeed, in the soil. Their roots draw them in and spread them around the terrestrial plants, and I have no doubt that they ultimately get exuded and end up in the solutions the epiphytes see. (For example, Alan Koch mentioned that rupicolous laelias are common to areas where the soils are particularly high in iron, so it should be enhanced in their feeding regimen.)

3) "Concentrations mattering less than ratios" is crap. (Forgive me, Mike. I'm trying to make a point.) An insufficient supply of the "ideal dietetic ratios" will still result in starvation. Considering the extremely dilute nature of those solutions the epiphytes see, I suppose one might conclude that in the case of orchids, ratios might be of more import, but I think the general statement is too broad to be valid.


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## Stone (May 8, 2015)

Ray said:


> > 3) "Concentrations mattering less than ratios" is crap.
> 
> 
> 
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## naoki (May 9, 2015)

Stone said:


> Now if I varied the ratios by the same factor of 10, for example 10 times less S or 10 times more Mg, I would kill the plant.
> That is hardly ''crap''



I think this part is the key; if the orchids can have a wide sufficiency range, then it becomes what Ray is saying. From the perspective of deficiency, it is the system where one limiting factor determines the growth rate (within the limitation of the plant physiology). I know that you all know this, but here is the quote from the growing media book (p. 147):

"... As far as nutrients are concerned, each nutrient is a separate necessity. One cannot substitute for another. Plant growth is limited by that nutrient in lowest supply... Increasing the supply of that nutrient will increase growth, as in Fig 14.3, until it is again limited by the nutrient in second lowest supply, ...."

So as long as there are sufficient elements, then photosynthesis (C supply) becomes the limitation. So the actual ratio doesn't matter as long as there is enough of each (Ray's view). But too much of some elements can cause the toxicity (via direct physiological problem or indirect effect of interference among minerals). If the sufficiency range is relatively narrow as Mike thinks, then the ratio starts to become more important.

I've been thinking more closer to Ray's perspective; epiphytes (slow growers) are quite flexible in sufficiency range, so as long as there is enough of each, they should be ok (but we all know that high EC can cause the problems with water uptake and root dehydration). But it's just my gut feeling.

Anyway, thanks for the gypsum topic, Mike. I started to read the chapter of the grow media book, and I agree with Mike that it is something interesting to experiment with. I'll wait to see what you will find out! 

Also Mike's recommendation of the grow media book was great! Here is the link to the book. The amazon price in the US has come down recently (but it is starting to go up again), and it covers a wide range of topics. It is quite a bit easier to read, and more practical than Marrchner's Mineral Nutrition of Higher Plants (which goes into scientific literature at a deeper level).

Lance's link to N/S ratio of Phal bellina is pretty interesting. Thanks for finding this, Lance! The abstract seems to be an overstatement (1:15 is the best). Statistically, it seems that they should have said that as long as S is lower than 1:15, the plants grew well. The grow media book mentions that S requirement vary widely among among taxonomic groups (p.197), so it is a good info!


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## Happypaphy7 (May 9, 2015)

Mike's original question has still not been answered. 

"Ratio among different elements available to plants mattering less as long as there is enough of all required elements" is rather different than saying ratio matters less than concentration. 

As much as I hate to stray away from the original topic, is there any good study done regarding how different orchids show deficiency symptoms of different elements? I don't think I've come across with good examples and many people tend to go by examples taken from very well studied food crops, which can be highly misleading as different plant groups show deficiency symptoms quite differently. 

Also, does that book mention N/S ratio ideal for paphiopedilums? Then again, even among paphs, there are subgroups that might or most likely have different requirements. 

By the way, Mike said orchids can survive years without any fertilizing, I'm not sure about years, but in the past I got lazy and never fertilized for at least full year. This is when I had just phals (straight sphag or straight bark), yellow dancing lady oncidiums (promix) and paph maudiae type hybrids (straight bark or promix). I watered them all with tap water. never fertilized for one full year or more.
Phals all grew well and flowered in time. Oncidiums grew well and flowered twice a year with many flowers. Paphs grew and flowered up to three times a year. I wonder if they can store nutrients in their leaves for very long time or maybe the potting mix maintain some fertilizers from earlier fertilizing? This I would say no because with all the watering, I would think almost all might have been washed away. hmmm no idea. or breaking down of mix that helped a little?


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## Stone (May 9, 2015)

naoki said:


> > So as long as there are sufficient elements, then photosynthesis (C supply) becomes the limitation. So the actual ratio doesn't matter as long as there is enough of each (Ray's view).
> 
> 
> 
> ...


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## Stone (May 10, 2015)

gonewild said:


> > Personally I know that a good supply of S is a benefit to the plant but since you started the thread and have said Rays plants are deficient of S even though they show no symptoms then you need to support that with proof of some sort.
> 
> 
> 
> ...


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## gonewild (May 10, 2015)

Stone said:


> gonewild said:
> 
> 
> > Actually, I found K-lite worked really well if I mixed it a little with a bloom booster which raised the P, K, NH4 and S concentrations.
> ...


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## myxodex (May 10, 2015)

One point I initially found confusing in the sulphur literature was the use of the terms S-limited and S-deficient.
S-limited means that there is insuffient S for the assimilation of available N. Most of the single component fertilisers are providing S at a limiting ratio simply because of the practical problem of CaSO4 precipitation. It is very easy to fix this situation, simply by adding a bit of tap/well water to your mix. Even rain water typically has a few ppm S courtesy of volcanoes and fossil fuel burning, so it is only in the exclusive use of RO water that S limitation is likely. In the wild, my guess is that orchids are far more likely to be N limited than S limited because of the S in rainfall and the fact that they need only 1/15 of the S as N.

One issue with S limitation that I think just might be worth consideration is oxidative stress. High light levels, toxic metals and pathogen infection are all situations in which plants are exposed to above background levels of reactive oxygen species (ROS). ROS cause damage, including mutation, and are neutralised by antioxidant systems, the most important of which are glutathione and vitamin C. In fact ROS are generated all the time during photosynthesis and the need for an efficient antioxidant system is continuous in all aerobic organisms, not only plants. The glutathione system is sulphur based and competes with protein synthesis for the supply of cysteine. In addition to the glutathione antioxidant system, there are other S compounds such as phytochelatins which bind toxic metals, phytoalexins (some of which are S containing) which are involved in pathogen defenses. These S compounds are all induced, i.e. rapidly synthesized on demand, so under S limitation this protective response to any additional oxidative stress is compromised. My guess is that chronic S limitation may be asymptomatic for the most part, but may result in plants that are less robust and more prone to accumulative genetic damage (senescence ?) than those that have adequate S. Also there are numerous papers out there about S and pathogen resistance in plants, just google it, and you will come across a whole field of research about SIR, "Sulphur Induced Resistance".


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## Stone (May 10, 2015)

gonewild said:


> Stone said:
> 
> 
> > The logical experiment for you is to try using k-lite and add only additional S. Then you will have the answer whether it is the S that made a difference or if it was the addition of one or all of the other nutrients.
> ...


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