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Dosing with Ammonia and Urea

Lisa_Perry75

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I was looking for chemical structures to show why the percentage of N changes and found this:-
http://bcn.boulder.co.us/basin/data/BACT/info/NO3+NO2.html
It is a good page with useful information on urea and ammonia. I might add that just because urea has more N %age wise it does not mean it will all be available for the plants. From what I can gather on that web page urea breaks down into ammonia and then oxidises to nitrate.
Urea
urea.gif

Ammonium (ammonia has 3 hydrogens)
Ammonium.gif

Nitrate
nitrate-1.png


And just to blow your minds I thought I'd add the structure of urease, just cos its beautifiul... I'm off to look at the structure in more detail!
urease.jpg
 

plantbrain

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When you folks add small daily amounts of N, urea or otherwise(NH4),

What do you think happens with the filter bacteria?
Do you think the colonies become larger?
Or smaller?

In other words, adding more NH4 is a bit like doing fishless cycling.
My point is how do you know that the plants are really getting most of it?

You really don't.......

What happens if the NH4 ends up as NO3?

I agree adding NH4 is not an issue as long as you at low levels, have no so intense light, decent care and stability etc.

Everyone that's done this gave up and went back to normal routines.
Or they decided to add and feed their fish each day.

You can measure and weight the amount of fish food to get a good idea how much NH4 comes from the fish waste.

About 90% is excreted, and 10% at best is retained in the fish.

So 90% of the fish food ends up as NH4 or is converted by bacteria to NO3. Urea is pretty quickly turned to NH4 in water.

Folk's use to use Schultz's African Violet drops here in SF the late 1990's.
A few algae outbreaks caused them to stop and switch to fish.

Seems simpler and less risk to just feed the fish.
I was never able to measure any growth rate differences.

Anyway, adding NH4 via the sediment is wiser and easier.
ADA As has it. and the outside of the grains quickly are oxidized by bacteria, but the roots can get at the interior parts of each grain that have the NH4 still in there.

If ADA As was hard, not soft, it would be too tough to have the root get at the NH4.

I think that is the main thing you see in ADA As and mud/soil sediments.
Water column dosing seems not worthwhile.
I think you end up making a much larger bacteria colony is all.

Anyway, plants CANNOT store NH4 inside, they can and do storage lots of NO3.

So you can either dose it daily, small little bits, risk toxicity, algae etc, or just add a few more fish.

Do we see dramatic differences based on fish loading?
No, not really.

So why do you think this would be much different?

Tell you want, keep adding progressively more and more NH4, urea and or fish to your tank.

See how much it takes to break the system.

It's going to be pretty variable.

Also, try removing your filter.
Try to rule things out.

You'll learn.


Regards,
Tom Barr
 

JamesC

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I have now finished my little experiment with dosing urea and can honestly now say I have noticed no difference to when I dosed no urea. Plant growth and appearance are exactly the same. Also I'm happy to say I didn't get any algae with adding the daily amounts of urea.

I shall now return to my normal urea free dosing.

James
 

ceg4048

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James,
Any theories of why the APC poster would have reported such dramatic differences? I still wish I understood whether the urea was being converted via nitrification or being consumed more directly as NH4. From Mr. Barr's explanation it sure seems like it is ultimately an NO3 uptake. Were you able to take any measurements? How did you arrive at your ppm values and do you think you would have the guts to up the dosages?

Cheers,
 

JamesC

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It's very hard to know what's going on but I have a suspicion that the urea is very rapidly removed by the filters before the plants have any chance of getting access to it. I'm always a little sceptical about what people say with their dosing schemes which is one of the reasons why I like to try different methods to see what the results are.

The amount of urea used was a value that I had seen other people use. I often go away for weekends so when I do I just dose the weekend amount before I leave. Seemed to cause no problem that I could see. Don't think I'd want to dose too much urea just in case.

Maybe urea dosing works better on lower light systems with no or few fish.

James
 

plantbrain

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James, using urea on lower light systems of any type will = less algae issues, this is true for ANY treatment.
I'd be careful not to assume that it's for only a lower light system.

If a test is really what folks are interested in, then setting a wider range of light levels or a high/very high light level would be the best to see how much, how long to destabilize things.

If you use the rational or logic that suggest if you can keep things easily stable at very high light, high CO2, high nutrients, then a very wide range is allowable at less light intensity, correct?

You can obviously get away with a lot more wiggle room at less light for most any treatment.
This is a simple logic that allowed me to use EI dosing to target any aquarium without much issue even with a wide range of light values.

At 4 W/gal, I could not add much NH4.
I had GW otherwise.
I could easily kill the GW with a UV, then repeat the test again after a few weeks to see and get more replications from the same system.
Then I tried adding progressively more fish.
Same results but a few different species of algae.

At low light, urea is fine, but so is adding more fish ;)
If you add high fish loads to high light tanks, what are the odds the tank will be more stable vs fewer fish?

I think many folks over look a lot when they rush to judgment and set up so called "test".
You need to be careful and make sure you know as you try and answer questions.

You also need to see what types of test you can set up that actually answer your question :idea:
Many of the test I've done over the years I happened upon and had a small epiphany. But I was suspicious of my results and wanted to be sure.

Later, I've gotten better :!:

But the idea to test it for yourself and see, rather than bandwagonieering, and suggesting someone's test or claim is right or not and sounds logical is a poor method.

Try it for yourself and see.
Prove it to yourself.
This type of approach and advice helps produce critical thinkers and folks that can answer questions, not merely parrot belief and statements said by others.

Regards,
Tom Barr
 

plantbrain

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BTW, this might help to see what urea does:

CO(NH2)2 - H2O + Urease => 2NH3 + CO2.

So adding it to water only requires urease, which many things in a rich juicy aquarium have.............thus it's rapidly converted to NH3/NH4 and CO2.

Here's a paper on the topic:
http://www.ncbi.nlm.nih.gov/pubmed/17268879

The epiphytes/bacteria and the sediment transform most of it.
Plants take up some, but overall, the bacteria seem to do most of the work.

http://www.staff.kvl.dk/~nogj/Aquatic/Urea/index.htm

Dr Reddy was my professor at UF.
He is the Man when it comes to cycling in wetlands.

http://wetlands.ifas.ufl.edu/publicatio ... -1997.html

Read a few of those.
When you are done, you'll know more than any aquarist about sediments.

I'm not sure why other folks have not bothered to look up things.
I guess they are scared of really learning.
It's not hard these days with the web either.

However, you still need to know what to look for, how to interpret what you find and apply it.

Regards,
Tom Barr
 

JamesC

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Some interesting reading there. Thanks for posting Tom. If I had the time and resources I would love to run some trials and learn more, but at the moment I can only judge by what I see in my tank.

James
 

plantbrain

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James et al,

Consider running smaller and simpler test on pots or terrestrial terrariums, small dinky tanks etc.
Less work, more rep's. Be creative with the designs.

Most do not have a bunch of tanks to play with, I used pairs and then run blocks over time.
But I spent less time doing scaping as a result.

Regards,
Tom Barr
 

ceg4048

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Hi Tom, OK, it seems as if every time I think I have a grip on one riddle I find that there are ten other riddles unaccounted for. I looked at the first link - the entire article can be found at the SpringerLink site: http://www.springerlink.com/content/m761n307t70t5p07/. The article is mindblowingly difficult to follow but what seems clear is that algae have no difficulty uptaking urea whether it is by direct uptake or by transformation via the "epiphytic biofilms" in the same way plants do. It is stated that "...Previous studies have found that urease enzymes can be intracellular, cell surface bound, or extracellular..." which sounds to me like the transformation can occur above, below or within the plant's tissue structure.

The article also states: "It was found that the urea transformation was 100 times higher in sediment ...compared with the epiphytic activity on the surfaces of the submerged plant Elodea canadensis..." There was some further correlation made between the available surface area of the plants in the aquatic zone being studied and the epiphytic transformation rate, i.e higher leaf square footage yields higher transformation rates.

What is not clear to me though is if the sediment does that much more transformation does that mean that a majority of the urea James was dosing found it's way into the substrate, was transformed by the substrate's urease, and then ejected from the substrate ultimately as NO3 after nitrification? If that is the case does this occur via flow in and out of the substrate, or would this happen at the surface of the substrate and distributed by filter flow? Also, does the filter count as an extension of the sediment in this case?

I looked further into urease and found a cool illustration of the active site of the enzyme: http://www.uni-regensburg.de/Fakultaete ... ease-e.htm

The more I looked at this though the more astonished I was by the explanation that the active site was an area of the molecule where two Nickel atoms are attached to a hydroxyl? :wideyed: So my question is, if urease is so abundant then it follows that Ni must also be abundant, but how?? We don't dose this so I'm even more dumbfounded. Are there different "species" of urease which use different, perhaps more abundant metals at the binding site?

Any clarification you could offer would be appreciated.

Cheers,
 

plantbrain

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Nickel does not need to be that abundant, after all, think about it, that urease enzyme gets used millions of times and only needs a few metal cofactors.

Relative to other nutrients and metals, there's very low demand for it.

Yes, filter bacteria do what sediment bacteria do: transform and use energy and reduced forms of N like NH4 are great sources.

I would not expect a lot of work form the epiphytes on plants, but there's still a lot of them, even if 100 times less.

A simple test, use Riccia in a bare bottom tank with CO2 etc and high light
No filter, no bacteria really etc, you could dip the plants into diluted Excel to kill bacteria etc and then grow it out.
Or just float Egeria etc in a bare bottom tank.

But yes, it's not this simple nice little system we are playing with here.
The effects we see might be due to increased filter bacteria colonies, not increased plant health.
Big filter colony able to remove larger amounts of NH4/urea= less chance for algae spores to get any NH4 to germinate.

Observations support this view as well.

By using 15N (stable isotope) labeled NH4 or urea, we can measure how much NO3 is transformed by bacteria and how much algae spores/algae adults and aquatic plants get.

This would be a wonderful test, something I've been thinking about for 8-9 years now.
It could answer many complex questions in our tanks.

Just fund me 50-100K$ and give me a year, I'll get right to it:)
The above study used the transformed products of respiration, rather than following the partitioning of Nitrogen.
I am doing the same type of thing with Excel in plant tissue as they did.

So filter, plants and sediment all are playing a role, I'm not sure how much each part contributes, but the evidence suggest bacteria play a huge role here.


Regards,
Tom Barr
 

JamesC

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I've been thinking a lot about this subject recently again and so have decided to bring this topic back to life. What I want to know is why do the likes of ADA, Seachem, Tropica, etc, all use ammonium or urea compounds in their fert solutions for a source of nitrogen. If it's so bad why take the risk of giving your product a bad name. There must be more to it. I don't for a moment believe they do it because of the small cost difference of potassium nitrate. I have even posted on other forums asking the same question but as of yet not got an answer.

Low ammonia levels don't worry me as I believe that it is beneficial to the plants. I keep lowish nitrate levels which then makes ammonia more favourable for uptake by the plants. This may explain why heavy nitrate dosers have more problems with ammonia as it is less favoured over nitrate. I may do some more testing with dosing urea using the levels of ammonium in TPN+ that I have worked out in this thread - http://ukaps.org/forum/viewtopic.php?f=11&t=3985&start=0.

James
 

GreenNeedle

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I don't think many suppliers would worry too much about the price of Pot Nitrate. Its phosphate supply in its various forms that sky rocketed last year to the point it was darned hard to get for the fert companies without pre-ordering heavy amounts (talking ordering whole year's supplies in advance to ensure supply)

Molybdenum and Molybdate are the other 2 rocketing elements within the ferts industry.

Garden manufacturers use both Pot Nitrate and organic sources in their products!!!

AC
 

JamesC

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Hi Peter,

Hadn't seen that before, thanks for posting. It contains urea + KNO3 + NH4NO3 in these amounts
1 ppm NO3
0.1 ppm NH4
0.33 ppm urea

Interesting that he also states this and I quote
Due to energetic reasons, it is slightly easier to absorp ammonium than nitrate. But higher nitrate concentrations diminish the ammonium absorption

This is what I've always been led to believe and is why I believe heavy nitrate dosers seem to have more problems with ammonia.

James
 

Voo

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I wonder how much Tropica would give away if you was to ask them why they use ammonium nitrate instead of potassium nitrate, and voice your concerns about adding extra ammonia to your tank?
 

ceg4048

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Well, the thing is that we have to be very careful on the broad statement as regards inhibition of nitrate uptake by the presence of ammonium. This is very species specific and may not be valid. In just about every botanical journal I've read there was no inhibition demonstrated, and in fact the rate of NH4 uptake very often exceeded the rate of NO3 uptake when both are present. Here is a typical report, although the focus of the tests were to determine the relative uptake of root versus leaf => Ammonium and Nitrate Uptake by the Floating Plant Landoltia punctata

Barr's data indicates that the preference is dependent on relative concentrations however, such that at high NH4 concentrations NH4 is preferred while at very low concentrations NO3 is preferred. This could also be species dependent.

In the DRAK shop website that zig provided it is stated "..Ammonium is absorbed instantly and mainly by water plants, but on the other hand, it can not be stored. Due to energetic reasons, it is slightly easier to absorp ammonium than nitrate..." What he is alluding to is that the energy cost for the plant to strip an NH4 ion of it's nitrogen is much lower than the cost of stripping the NO3 ion. NO3 has to be reduced by a chain of various enzymes such as nitrate reductase and nitrite reductase. On the other hand NH4 buildup in the tissues is toxic to the plant so that accumulation of NH4 requires that it be converted to, and actually stored as NO3.

I completely disagree with his contention that the "optimum" nitrate concentration is on the order of less than 10ppm. I mean, that is in complete conflict with my observations. The more nitrate I add the faster the growth, assuming all other nutrients are unlimited, naturally. I see no evidence whatsoever that any plants I've grown respond poorly to high nitrate levels.

I see no evidence that the presence of nitrate inhibits ammonium uptake, although I'm less confident about this since I have no means of measuring such a phenomenon and since it is extremely difficult to separate an ammonium uptake metric from ammonium attenuation via bacterial nitrification. I assume that if the bacterial colonies are robust then there is no need to worry about NH4 uptake inhibition in plants simply because the bacteria will do the work for you.

Cheers,
 

JamesC

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I'm going to have another longer term trial of dosing my tank with urea. All plants grow well except for two that look like they are suffering a calcium deficiency. The two are Alternathera Reinekii and Ludwigia Glandulosa which are also the only hard stem type plants I have.

For those interested this is what I plan to dose daily on my 200 litre tank:

3.3g Potassium Nitrate
2.0g Urea
10.0g Potassium Sulphate
0.9g Potassium Phosphate
8.0g Magnesium Sulphate
500ml Water

5ml Tropica TPN equivalent Trace

25ml of the macro solution gives:
0.5ppm NO3
0.5ppm Urea
0.15ppm PO4
1.5ppm K
0.2ppm Mg

Interestingly for me anyway is that both the NO3 and urea nitrogen content is exactly the same as I currently dose which is 1.5ppm NO3.

James
 

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