# Phosphorous Toxicity



## Candace (Jan 21, 2008)

Leo brought this up in another current thread and I think it deserves a thread of its own. I've got a couple of sanderianum hybrids that have some yellowing leaves and one trusted grower and AOS judge thought it may be due to Phosphorous toxicity. Are sanderianums simply prone to this? Others? I'm mainly using MSU at 125N for the last year and the leaves are looking better but not great. Prior to using MSU I rotated with several different fertilizers. What are the symptoms of this toxicity and what do I need to do? My sanderianum hybrids and my Jerry Spence are the only paphs in my collection that seem bothered by it.


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## Heather (Jan 21, 2008)

There's a thread wandering around here somewhere (I think posted by Xavier - Sanderianum) about this subject. I'll try to find it.

Edit - it may be at SOF. I didn't find it here.


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## likespaphs (Jan 21, 2008)

i'm not entirely sure, but i think it presents itself as interveinal chlorosis (with the veins still green). but then again, it may interfere with micro nutrients and show up as them....
a search for nutrient toxicity plants gave me a few helpful hits. an image search for phosphorus toxicity showed me a lot of pictures of reefer but they have lots of good info so you may want to compare....

click this link for a decent overview...


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## Candace (Jan 21, 2008)

Yeah, I remember reading something about this a while back but I didn't really focus on it as I wasn't having a problem.


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## Candace (Jan 21, 2008)

> interveinal chlorosis with the veins still green


 This is what I'm seeing. I did a search on nutrient deficiency and couldn't find much on phosphorous toxicity. I will try to post some photos, but I'm dealing with server problems this weekend.


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## gonewild (Jan 21, 2008)

It is not likely that you are seeing phosphorous toxicity. But phosphorous applied at amounts out of balance with other nutrients will cause other nutrients to become unavailable to the plants. 

At high levels phosphorous does make nitrogen unavailable for plant uptake. That could account for the pale leaves.


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## Eric Muehlbauer (Jan 21, 2008)

Just curious....what is your growing medium? Eric


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## SlipperFan (Jan 21, 2008)

Thanks, likespaphs -- that's a great resource.


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## Rick (Jan 21, 2008)

Out of all my multiflorals my sanderianums (and a MK) turned out to be the least appreciative of bright light and warm temps, and were pale and slow growing until I gave them something closer to phal conditions. Now their growth rate and color is about as fast as any other multi in my collection.

There was also a thread a ways back that sanderianum was very sensitive to high iron.


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## Leo Schordje (Jan 23, 2008)

Symptoms of nutrient surplus start as a hard black leaf tip die back - especially starting with newer growths first rather than the oldest growths. Also, Lance is right, excess phosphorous does make other nutrients unavailable. This is severly aggravated if you dry the plants out too much between waterings. Root tips also die, eventually root loss kills the plant. Symptoms are not terribly specific, but I did notice a pattern of loosing my most valuable plants (usually the salt sensitive species) after using 'blossom booster', I then had a long talk or two with Jan Szyren of MSU - Lansing, and I became convinced I had 2 problems - excess phosphorous and drying the plants too hard between watering. I switched to MSU 5 years ago and my plants are vastly improved. Read the literature, it is too lengthy a discussion for me to type here. But the best fertilizer regime for orchids is one that is frequent, dilute and high nitrogen, low phosphorous, high potassium and a goodly dose of Calcium, magnesium, & sulfur, and lesser amounts of copper, manganese, iron, and the rest of the micro-nutrients. Another key benefit of MSU formula is that Ca, Mg, & S are macro nutrients rather than micro-nutrients. I swear by the stuff. 
.................. Candace - if you have been using MSU at 125 ppm, your problem is NOT excess phosphorous. If all your plants have been repotted since you switched to MSU you should not be having any toxicity issues due to nutrient excess. You did not mention how often you use the MSU, but 125 ppm N is at the low end of the dose range for continuous feeding, if you are not feeding this at every watering you may actually be starving you plants a bit. I would up you dose rate to about 200 ppm. N this might do you better. 
Also sanderianum hate cool, they want Phal temps, and they don't want to dry out between waterings. Those are my thoughts
Leo


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## Candace (Jan 23, 2008)

Thanks for your comments, Leo. Since I grow in leca in s/h I don't have a problem with excess drying. I was thinking along the same lines as Rick that maybe the sanderianum hybrids were receiving too much light. But my other paphs are happy with the light levels and fertilizer. They aren't getting below 58 at night. I'm also not seeing the leaf tip die back. I can try upping the dosage of my fertilizer, but was worried that if I did that it may just make the problem worse. But I guess trial and error will be the key.


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## Leo Schordje (Jan 23, 2008)

Going from 125 to 200, or even 250 ppm is still a very dilute solution. I would not worry. 
.
Now if you jumped up to 1500 ppm you might end up in trouble. 

Leo


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## Scooby5757 (Jan 23, 2008)

Leo Schordje said:


> .................. Candace - if you have been using MSU at 125 ppm, your problem is NOT excess phosphorous. If all your plants have been repotted since you switched to MSU you should not be having any toxicity issues due to nutrient excess. You did not mention how often you use the MSU, but 125 ppm *N* is at the low end of the dose range for continuous feeding, if you are not feeding this at every watering you may actually be starving you plants a bit. I would up you dose rate to about 200 ppm. N this might do you better.
> Also sanderianum hate cool, they want Phal temps, and they don't want to dry out between waterings. Those are my thoughts
> Leo


 (color emphasis mine)

I need to ask to clarify this in my head. When you say 125 ppm and 125 ppm N, are you referring to just ppm, as if to say I have water with fert in it, and then stick my gauge in and it says 125 or are you say that by looking at the amount of N in the fert you have deduced though some kinda equation what the ratio of fert to water is so that the N alone is 125 ppm and all the other nutrients are not included in this count??


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## cnycharles (Jan 23, 2008)

Candace said:


> Thanks for your comments, Leo. Since I grow in leca in s/h I don't have a problem with excess drying. I was thinking along the same lines as Rick that maybe the sanderianum hybrids were receiving too much light. But my other paphs are happy with the light levels and fertilizer. They aren't getting below 58 at night. I'm also not seeing the leaf tip die back. I can try upping the dosage of my fertilizer, but was worried that if I did that it may just make the problem worse. But I guess trial and error will be the key.



One problem I've had with s/h with warm species (not paphs) and trying a yellow besseae in like conditions is that with the s/h the roots and base of the plant are usually a fair amount cooler than the air temp; if the plant likes it warm and you use s/h the plant itself may be a bit cool. One problem that was pointed out with high phosphorus was forced nitrogen deficiency, this usually happens with cool and wet conditions where the plant isn't taking things up very quickly. Warming up the area a bit for this plant (base heat would be great) might fix some of these problems. When I took the yellow besseae and put it into large diatomite and in with my phals (not sitting in water believe it or not) the plant did much better.


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## Candace (Jan 23, 2008)

> I need to ask to clarify this in my head. When you say 125 ppm and 125 ppm N, are you referring to just ppm, as if to say I have water with fert in it, and then stick my gauge in and it says 125 or are you say that by looking at the amount of N in the fert you have deduced though some kinda equation what the ratio of fert to water is so that the N alone is 125 ppm and all the other nutrients are not included in this count??



I'm talking about 125ppm Nitrogen. My TDS(total disolved solids) is much higher than that.



> Warming up the area a bit for this plant (base heat would be great) might fix some of these problems.


 I don't think the temp. has anything to do with my problem since it doesn't disappear when it's much warmer either. I did notice that they greened up a little when I started using MSU a year ago. But they're still not normal looking. I think I'm going to up the fertilizer and see what happens. If they get worse than I can go from there. 

Thanks for the suggestions. I'm interested in the possible iron problems with sanderianum as well. I'll have to google to see what I find.


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## Rick (Jan 23, 2008)

We had a pretty good debate going with regards to iron on a thread on this site a year or so ago. I'm not convinced especially if you are using RO water and MSU fert. Some domestic waters are pretty high in iron, but bioavailability of iron is low unless the pH is low too (which I guess could happen in the bottom of a semihydro pot).

To be more explicite on light levels I think the bulk of the time they should be under 1000 - 1500 fc, which is phal or barbata paph levels of light. They also like LOTS of airflow and very high humidity. I had a hard time with them until I moved them low into the center hallway of the greenhouse with vigorous airflow and humidity not less than 70%. Mine always tend to grow into the isle too, so they are kind of hanging out the side of their pots growing away from what light they get and into the air current.


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## Candace (Jan 24, 2008)

Thanks Rick. I try to keep my water and fertilizer in the high 6 low 7 ph range and yes, I use R.O. so I'm probably not over-doing. I get a LOT of light in my g.h. and will try a shadier spot as well as upping the fert. to see if those changes help.


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## Leo Schordje (Jan 24, 2008)

Scooby5757 said:


> (color emphasis mine)
> 
> I need to ask to clarify this in my head. When you say 125 ppm and 125 ppm N, are you referring to just ppm, as if to say I have water with fert in it, and then stick my gauge in and it says 125 or are you say that by looking at the amount of N in the fert you have deduced though some kinda equation what the ratio of fert to water is so that the N alone is 125 ppm and all the other nutrients are not included in this count??



The 125 ppm N means I did the calculations based on the Nitrogen only. The other measure would be to write it as TDS (total dissolved solids). For myself, my tap water is about 225 ppm TDS, a 125 ppm N dose of MSU RO Formula would add about 750 ppm TDS to the water, so I actually am watering my plants with water that is about 975 ppm TDS. This may sound like a lot, but it is not. Phrags love water like this. The key is to avoid a hard dry out of the plants. When you dry out the plants, in the last of the remaining water film the TDS soars, and this is when the salt damage occurs. Many commercial operations are irrigating with water that is approaching 2000 ppm TDS. For operations growing 'dirt plants' the TDS may be even higher. Key is to not over think this whole thing. Settle on a nice dilute but (strong enough to be) effective fertilizer regime, get your watering pattern right and step back and watch the plants grow. 
Leo


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## cnycharles (Jan 24, 2008)

Leo Schordje said:


> The 125 ppm N means I did the calculations based on the Nitrogen only. The other measure would be to write it as TDS (total dissolved solids). For myself, my tap water is about 225 ppm TDS, a 125 ppm N dose of MSU RO Formula would add about 750 ppm TDS to the water, so I actually am watering my plants with water that is about 975 ppm TDS. This may sound like a lot, but it is not. Phrags love water like this. The key is to avoid a hard dry out of the plants. When you dry out the plants, in the last of the remaining water film the TDS soars, and this is when the salt damage occurs. Many commercial operations are irrigating with water that is approaching 2000 ppm TDS. For operations growing 'dirt plants' the TDS may be even higher. Key is to not over think this whole thing. Settle on a nice dilute but (strong enough to be) effective fertilizer regime, get your watering pattern right and step back and watch the plants grow.
> Leo



Ah, that's why I burned my plants; they got fed when the roots were dry.


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## Ray (Jan 26, 2008)

Hey Leo - 

You brought up something I've been wondering about when it comes to fertilizer concentrations (and something I keep forgetting to ask Bill Argo):

According to the MSU RO label, if I want 125 ppm N, I have to add 3.55 g of the powder to a gallon of pure water. If you calculate 3.55g/3785.412 g water, the calculated TDS is 938 ppm, but I'm reasonably sure that some of the anions - the oxygens in the carbonates and sulfates, for example - and stuff like the extra hydrogens and oxygens in the boric acid don't really count as dissolved solids. However, if you go with the elemental cations only, the calculated TDS is about 355 ppm.

Like you, I believe in frequent, dilute feedings, and at those concentrations, it doesn't really matter which number is "correct" (it's probably somewhere in between), but for folks who prefer to feed more strongly but less frequently, it would be nice to get a handle on it.

Any ideas?


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## Corbin (Jan 27, 2008)

Scooby5757 said:


> (color emphasis mine)
> 
> I need to ask to clarify this in my head. When you say 125 ppm and 125 ppm N, are you referring to just ppm, as if to say I have water with fert in it, and then stick my gauge in and it says 125 or are you say that by looking at the amount of N in the fert you have deduced though some kinda equation what the ratio of fert to water is so that the N alone is 125 ppm and all the other nutrients are not included in this count??



(desired nitrogen contentration) X (# gallons of water) 
_____________________________________________

(% nitrogen in the fert.) X 75

The answer to the equation is ounces of fert. to add to achieve a set N concentration


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## Ray (Jan 28, 2008)

Another rough calculation method to find out how much to use to get 125 ppm N is to divide 10 by the %N on the label. The result is in teaspoons per gallon, and if you round up or down, you'll still be in the ballpark.


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## NYEric (Jan 28, 2008)

Yes phosporous is toxic and combustable in water!


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## Leo Schordje (Jan 28, 2008)

Ray,
I would have to go to Bill Argo myself. I try to avoid using a calculator once I leave work,  
I really do recomend people follow the dilute and frequent fertilization program, this allows a nice wide margin of error. 
Thanks for helping on this topic, your website is a wealth of information.
Leo


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