# Ammonia vs nitrite vs nitrate



## Malawi

Hi

There was a litle discussion on another board (non english) about what the plants prefer to use as nutrition.

One view was that the plants prefered Ammonia over nitrite, but would use nitrate when the two former was exploited.

The other vie was that the plant prefer Ammonia, cannot use nitrite, but would use nitrate when there was no Ammonia. According to this view the nitrite might pe poisonous to the plants.

Now I hope to get more info on the subject, since there seems to be a lot of knowledge on this forum, I am trying here.
Are one of the former "statements" correct, or is it something inbetween?


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## bgzbgz

http://www.aquabotanic.com/plants_and_biological_filtration.htm


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## helgymatt

Nice question!

First off, plants will use Ammonium (NH4+), not ammonia(NH3). In the biological process, plants will convert ammonium to nitrite by bacteria call _Nitrsomonas_. Nitrite is usually very quickly converted to nitrate, by more agressive bacteria, _Nitrobacter_. Nitrite is known to be toxic to terrestrial plants, even at low levels. The same is true for aquatic plants. So plants can utilize nitrogen either in the form of ammonium or nitrate. Some plants have a preference of one over the other, but most don't.

In a well planted tank, fish waste will will release ammonia, which is toxic to fish. Often, that ammonia quickly gains a hydrogen and forms ammonium, but the process is pH dependent. This article explains it much better than I can.... http://www.extension.iastate.edu/CropNews/2008/0421JohnSawyer.htm

So, ammonia fish toxicity is more of a problem the higher the pH is, but even so, small amounts of ammonia are toxic. In a cycling aquarium, we fertilize with nitriate because the biological process will convert ammonium fertilizer to nitrate anyway. I believe we don't use ammonium fertilizers because they pose algae issues, but I have heard contradictions to this so this may not be true.


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## Malawi

helgymatt said:


> Nice question!
> 
> First off, plants will use Ammonium (NH4+), not ammonia(NH3). In the biological process, plants will convert ammonium to nitrite by bacteria call _Nitrsomonas_. Nitrite is usually very quickly converted to nitrate, by more agressive bacteria, _Nitrobacter_. Nitrite is known to be toxic to terrestrial plants, even at low levels. The same is true for aquatic plants. So plants can utilize nitrogen either in the form of ammonium or nitrate. Some plants have a preference of one over the other, but most don't.


I am used to just using the term Ammonia, although this is as you say not completely correct. I will try to distinguish Ammonium/Ammonia as there clearly are a difference.

I may be out on a limb here, but I feel pretty confident that the plants can take up ammonium without help from bacterias. And that ammonium to nitrite convertion only happends by bacteria if there are not enough plants to absorb it.

The third point in this paragraph goes right to the core of the discussion I refered to.
In the link bgzbgz posted, there are a small section about it, and a graph (fig 3)

I'll just paste the section here, since this is what the debate revolved around.

--Snip--
Nitrite Uptake by Plants

Although plants can use nitrite as an N source, the pertinent question for hobbyists is- Do aquatic plants remove the toxic nitrite before the non-toxic nitrate? I could not find enough studies in the scientific literature to state conclusively that they do. However, the chemical reduction of nitrites to ammonium requires less of the plant's energy than the chemical reduction of nitrates to ammonium. (A plant must convert both nitrites and nitrates to ammonium before it can use them to make its proteins.) Thus, it is not surprising that when Spirodela oligorrhiza was grown in media containing both nitrate and nitrite, it preferred nitrite (Fig. 3).
--Snip--

As one can see, this suggests that nitrite may be benificial to aquatic plants, even though it is considdered poisonous to surface plants.
It may be a measuring error (maybee there were nitrobacters in the sample), and it may be that the Spirodela O. does not represent the typical aquatic plant. But there are something there worth to follow, and it would be nice to be more certain about this.


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## helgymatt

Malawi said:


> I may be out on a limb here, but I feel pretty confident that the plants can take up ammonium without help from bacterias.


For sure!


Malawi said:


> And that ammonium to nitrite convertion only happends by bacteria if there are not enough plants to absorb it.


Maybe, but this oxidation will probably always take place at some level no matter how much the plants uptake. Remember that the plants are not absorbing the ammonium all at once.



Malawi said:


> The third point in this paragraph goes right to the core of the discussion I refered to.
> In the link bgzbgz posted, there are a small section about it, and a graph (fig 3)
> 
> I'll just paste the section here, since this is what the debate revolved around.
> 
> --Snip--
> Nitrite Uptake by Plants
> 
> Although plants can use nitrite as an N source, the pertinent question for hobbyists is- Do aquatic plants remove the toxic nitrite before the non-toxic nitrate? I could not find enough studies in the scientific literature to state conclusively that they do. However, the chemical reduction of nitrites to ammonium requires less of the plant's energy than the chemical reduction of nitrates to ammonium. (A plant must convert both nitrites and nitrates to ammonium before it can use them to make its proteins.) Thus, it is not surprising that when Spirodela oligorrhiza was grown in media containing both nitrate and nitrite, it preferred nitrite (Fig. 3).
> --Snip--
> 
> As one can see, this suggests that nitrite may be benificial to aquatic plants, even though it is considdered poisonous to surface plants.
> It may be a measuring error (maybee there were nitrobacters in the sample), and it may be that the Spirodela O. does not represent the typical aquatic plant. But there are something there worth to follow, and it would be nice to be more certain about this.


I wouldn't argue that plants cannot take up nitrite, but I will say that at some level it will become toxic, just as very high levels of ammonium and nitrtate can become toxic in plants. I'm sure its the case that it takes much less nitrite to lead to toxicity than nitrate or ammonium. Again, I'm basing most of this on terrestrial plant research and it gets kinda cloudy with submersed plants.


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## helgymatt

Diana Walstad's book covers some stuff on nitrite uptake by plants also. Take a look at that if you have it.


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## Malawi

helgymatt said:


> Diana Walstad's book covers some stuff on nitrite uptake by plants also. Take a look at that if you have it.


I have just ordered the book today.
They seem to be a bit hard to find, so I ordered a couple extras to resell at my local club.

BTW: The link that bugzbugz refered to was written by Walstad, but is a bit unconclusive.


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## Malawi

helgymatt said:


> For sure!
> I wouldn't argue that plants cannot take up nitrite, but I will say that at some level it will become toxic, just as very high levels of ammonium and nitrtate can become toxic in plants. I'm sure its the case that it takes much less nitrite to lead to toxicity than nitrate or ammonium. Again, I'm basing most of this on terrestrial plant research and it gets kinda cloudy with submersed plants.


Seems like we are pretty much in tune.

I hope that cloud can be lifted.


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## Diana K

Nitrifying bacteria is actually Nitrospiros spp. 

Ammonia = NH3 (greater % of ammonia in higher pH water, and this is the one that is more toxic to fish in part because they cannot keep it out of their system)
Ammonium = NH4+ (greater % of ammonium in low pH water, and this is less toxic)

Most aquatic plants prefer these. (I am not sure if they can use one or the other better/faster/ or not at all)

Plants can also use nitrite and nitrate. (NO2 and NO3) but most plants prefer ammonia (or ammonium?)

Lots more info in Diana's book. Very thoughtful of you to order more to share with friends!


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## Singtoh

Hello All,

Just wanted to pass this along. About a month ago I experimented with using normal potted plant tabs pushed deep into my substrate. I used them very sparingly, but I have a gravel substrate and the ferts(NH4+,Phosphate and potassium) leached into the water column. The next day I decided to test my total ammonia and it was 2mg/l. Needless to say, I freaked and I did a 70% water change. This, after searching the internet, I came to the conclusion was the wrong thing to do, because my PH is always at 6.5-6.6 and therefore the Free Ammonia-Nitrogen Concentration was 0.004517mg/l according to this calculator: http://cobweb.ecn.purdue.edu/~piwc/w3-research/free-ammonia/nh3.html, and IMO doing such a large water change made the PH rise, until the CO2 was able to bring the PH back down to 6.5-6.6.(I may be wrong) After all this, I had no ill effects on my tank, and no visable algae and all is well. I have a heavily planted community tank with various species of fish, apple snails, cherry shrimp and ghost shrimp and no death of anything that I could see. 24 hrs. later my total ammonia was back to 0 and plants are pearling and happy as are all the critters. So, I guess between the plants and the bacteria in my filter it was consumed. I won't use these things again, but just wanted to pass along my experience. Just my 2 cents worth.

Cheers,

Singtoh


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## brenmuk

Malawi said:


> Hi
> 
> There was a litle discussion on another board (non english) about what the plants prefer to use as nutrition.
> 
> One view was that the plants prefered Ammonia over nitrite, but would use nitrate when the two former was exploited.
> 
> The other vie was that the plant prefer Ammonia, cannot use nitrite, but would use nitrate when there was no Ammonia. According to this view the nitrite might pe poisonous to the plants.
> 
> Now I hope to get more info on the subject, since there seems to be a lot of knowledge on this forum, I am trying here.
> Are one of the former "statements" correct, or is it something inbetween?


I think this is kind of an academic question because on a practical basis if you add NH4/or NO2 as a one off fert then you risk toxicity to fish etc and NH4 spikes have been put forward by Tom Barr as triggers for algae growth.
If you add NH4/NO2 on a regular basis your biological filtration will adapt to the higher levels and produce more NO3 (or your plants will get it first) but why bother risking toxicity/algae?
If you want to add extra NH4 then just add extra fish - they produce it constantly .


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## Singtoh

brenmuk said:


> I think this is kind of an academic question because on a practical basis if you add NH4/or NO2 as a one off fert then you risk toxicity to fish etc and NH4 spikes have been put forward by Tom Barr as triggers for algae growth.
> If you add NH4/NO2 on a regular basis your biological filtration will adapt to the higher levels and produce more NO3 (or your plants will get it first) but why bother risking toxicity/algae?
> If you want to add extra NH4 then just add extra fish - they produce it constantly .


I agree Brenmuk, I put those tabs in and then realized that they were made with NH4+. If I add anymore, I will get the proper tabs, but everything is doing fine. So if it ain't broke don't fix it i guess. I just wanted to relay my experience that I probably messed up a bit by changing so much water cause my PH was 6.5 which means the Total Ammonia reading was relativley harmless. Even after changing 70% of the water the Total Ammonia reading was exactly the same due to the tabs still leaching into the water, so what is one to do. The next day it was fine.

Cheers,

Singtoh


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## Zapins

Why use NO2 when you can use urea which is preferred by plants? Urea is not toxic like ammonia and nitrite so you don't have to worry about playing with fire.

Urea is quickly converted inside the plant into a valid N source with far less energy then it takes to convert NO3 to a nitrogen source.


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