Old NO3 growth optimal test from Paul Krombholz

[Tom Barr]

I was thumbing through a well known, but older Limnology text (Hutchinson, 1975, Vol 3 Limnological Botany pg 351-357) when I saw a nice graph showing growth rate vs NO3 concentration.

It seems Paul had found that 20 ppm N-NO3 and above was the ideal range for submersed plant growth(Vallisneria americana) back in the 1960's(1966). I suppose I redisocovered this range(20-75ppm) independently some 30 years later.

What is interesting is that we both arrived at the same range. At progressively high concentrations, this high rate of growth slowly decline, but very slowly.....even at 100ppm N-NO3 etc.

This also mirrors my own observations when I did longer term NO3 at 75ppm for several weeks.

What is really interesting is how rapid the growth rate increases when the level is maintained.

For exampleN-NO3)
At 5 ppm the rate of growth is greatly reduce, about 2.2/0.7= 3.14 times less growth (dry weight mass).
At 10ppm, the growth was about 1/2, 2.2/1.1 = 2x less growth than at 20-80ppm.
After 20ppm, the plant's growth is no longer nitrogen limited.

Fast forward to the molecular age of plant biology.
Why might these plants show this pattern? How would they control it?
Given what is known about LAT and HAT transportors for NO3, it may now be suggested that when plants have all their constitutive and inducible transporters upregulated and maintained, they grow faster and have non limited growth.

In order for the plants to do this, 20-30ppm of N-NO3 needs to be present in the medium(the water column). Now we have a plant that is healthy and can grow at a maximum rate. If the NO3 levels varies between say 2-15ppm, then the various transporters will be degraded and more efficient transports(the HATs) specific to low N-NO3 levels will be put in their place. As a result, the plants growth rate will be reduced.

It takes more energy to concentrate nutrients when there is less in the external environment. So at higher levels, the plants use different transportors that take full advantage of the higher N-NO3 levels and grow faster as result.

Which is about what we find to be optimal for growth in the water column.
Seems the data was and has been there all along, just no one bothered to listen to Paul, nor look stuff up.

He looked at many lakes and plants and did a lot of tissue analysis beside this as well.

Reference:

Gerloff, G.C., and Krombholz, P.H., 1966. Tissue analysis as measure of nutrient availability for the growth of aquatic plants. Limnological Oceanography, 11:529-537. (Hutchinson, 351-357)

Regards,
Tom Barr

 

[Tom Barr]

http://links.jstor.org/sici?sici=0024-3590(196610)11:4<529:TAAAMO>2.0.CO;2-X

Regards,
Tom Barr

 

[RlxdN10sity]

So are you suggesting that planted tanks should run at 20-30ppm NO3 and about 2ppm PO4? I run 1ppm PO4 and 5-10ppm NO3 with high light and CO2 should I increase PO4 and NO3? Should the increase occur incrementally over time or all at once? Thanks.

 

[Tom Barr]

All I am saying is that Paul's data suggest this.It may not apply to every plant species, but does for some certainly, such as M umbrosum, a known NO3 loving plant.


Regards,
Tom Barr

 

[jerime]

Interesting fact. It poses conflicting issues : maintaining high concentration of NO3might interfere with our wishes of increasing the plant's red colors as we always say that we need to lower NO3 concentration to increase anthocyanin concentration, hence redder plants.
So in light of that I have 2 questions :
1. How do we maintain stronger red color in plants (ignoring the fact that redder plant means stressed plant).
2. When anthocyanin concentration increases, what role exactly do they play with photosynthesis? (do they photosynthesize themselves or just aid the clr (a and b) to themselves?

 

[Tom Barr]

Interesting fact. It poses conflicting issues : maintaining high concentration of NO3might interfere with our wishes of increasing the plant's red colors as we always say that we need to lower NO3 concentration to increase anthocyanin concentration, hence redder plants.
So in light of that I have 2 questions :
1. How do we maintain stronger red color in plants (ignoring the fact that redder plant means stressed plant).
2. When anthocyanin concentration increases, what role exactly do they play with photosynthesis? (do they photosynthesize themselves or just aid the clr (a and b) to themselves?

Why is a stressed red plant a desired condition?
There are plenty of red plant species that do not require low NO3, many red species look pretty red when given good nutrition.

Anth's play a few plausible roles.
UV protection and anti herbivory are the most popluar.

When folks talk about plant growth and what it prefers, I think it's very safe to say that over expression of red is bad and sign of stress, hardly preference or optimal conditions for the plants.

Many species are available that will be a very nice red color without playing that razor's edge with NO3.

The main point of the research I see is that you have a large decrease in plant growth with only 10-15ppm decline in NO3 from 20 to 5ppm.

Very large.
400% less growth.

If you think that is a trivial amount, you may want to think again.

What happens if you drop the NO3 to 2ppm?
Or only a sub ppm?

BGA pops up pretty fast. Adding more CO2 and NO3 helps address that.
If there is little NO3 and decent NH4 and organic matter(leaching from stressed plants), makes sense, the BGA have good place to grow since the plants cannot.
Same deal with CO2 changes, and BBA, GW with NH4 and so on........

If you really want to maintain a low NO3, it's actually not that hard, but you need to use low light.

Low light=> less uptake demand for CO2=> less demand for NO3.
You have a lot more wiggle room between red stressed plant and permanent deficiency as demands and growth rates are less.

But then someone claims high light helps.
No, it does not.

High light increases NO3 uptake(and CO2 as well) and if you had a nice stable 5ppm, now the plant get redder because the growth rate increased, but you did not add more NO3. Often such tanks have troubles over time maintaining such red color but it's possible, just hard to do consistently over time.

So you get a few pics of super red plants here and there, some re touched photos etc.

Perception of color from person to person is very arbitrary as well.

R macrandra has done best at about 2-3w/gal of normal output FL's.
That's about 1 to 2.2 w/gal of PC.

Regards,
Tom Barr

 

[pelmato]

bonjour,
(first sorry for my bad english, wish i could developpe more...)

i have some R.mancranda for a while...and doing grate whit it.
last month my co2 was empty...
it take me 2 week to refile it...

first...my set up:
~200g (60x36x22inch)
10x 32watts T8 zoo-med (flora sun + reef sun)
flourite and sand (50-50% where the mancranda take place)
no liquid ferts added (only dry Kno3, when needed)
no water change for 3-4 month now.
No3 = 5ppm
po4 = 0ppm
co2= 20-25ppm

on the picture
#1 is the color that R.mancrada have whit CO2
#2 is new leaf (one week) whit no CO2

for now, my CO2 is back on track...and new leef of R.macranda is red again...

what can we suppose in that case ?
red color need CO2 or the poor CO2 make no more carence of no3 ?

 

[PaulB]

Hi Tom, can you name the red plant species that do ok in high NO3 conditions.

 

[Tom Barr]

Sure, these damn weeds:
L pantanal, L cuba, L arcuata

All at high NO3, 30ppm etc
Also note the red color without CO2.
Then look at the lighter color with CO2.

Developmentally, the plant can produce a lot more Red color if .........it's grown better. While less CO2 will help slow growth, at 1.5 to 1.6w/gal of T8 lighting in a large tank can go either way, but a plant can produce more anthocyanins if it has more carbon as those colored pigments are mainly unsaturated carbon chains.


Regards,
Tom Barr

 

[paludarium]

Sure, these damn weeds:
L pantanal, L cuba, L arcuata

All at high NO3, 30ppm etc
Also note the red color without CO2.
Then look at the lighter color with CO2.

I've heard that some plants are red not because of anthocyanins, but due to betalains, which contain nitrogen atoms. Maybe L. pantanal, L. cuba and L. arcuata contain betalains, therefore they are red at high NO3?

 

[PaulB]

Sure, these damn weeds:
L pantanal, L cuba, L arcuata

All at high NO3, 30ppm etc
Also note the red color without CO2.
Then look at the lighter color with CO2.

Developmentally, the plant can produce a lot more Red color if .........it's grown better. While less CO2 will help slow growth, at 1.5 to 1.6w/gal of T8 lighting in a large tank can go either way, but a plant can produce more anthocyanins if it has more carbon as those colored pigments are mainly unsaturated carbon chains.


Regards,
Tom Barr

Damn , wouldn't you know it only one of these plants ( L arcuata) is available in Oz and it's already a weed in my tank

Paul

 

[Tom Barr]

Ahhh it's a nice weed though.

Go collect some Eustralis stellata, it's native to Oz

Regards,
Tom Barr

 

[Marcel G]

It seems Paul had found that 20 ppm and above was the ideal range for submersed plant growth(Vallisneria americana) back in the 1960's(1966). I suppose I redisocovered this range(20-75ppm) independently some 30 years later ...
At 5 ppm the rate of growth is greatly reduce, about 2.2/0.7= 3.14 times less growth (dry weight mass).


At 10ppm, the growth was about 1/2, 2.2/1.1 = 2x less growth than at 20-80ppm.


After 20ppm, the plant's growth is no longer nitrogen limited.


Reference: Gerloff, G.C., and Krombholz, P.H., 1966. Tissue analysis as measure of nutrient availability for the growth of aquatic plants. Limnological Oceanography, 11:529-537. (Hutchinson, 351-357)

This seems to be a crucial argument for setting up the proper nutrient concentrations for Estimative Index method by Tom Barr.


The problem is that in the paper by Gerloff and Krombholz all the values are as NO3-N, not NO3 alone. So when Gerloff and Krombholz say that at 4.2 ppm the plant yield is 0.70 g DW (dry weight), 10.5 ppm => 1.14 g, 21 ppm => 2.32 g etc. it means that if we want to convert these to NO3 values, we need to multiply them by a coeficient of 4.43. So 4.2 ppm NO3-N = 18.6 ppm NO3 which yielded 0.70 g of dry weight, 10.5 ppm NO3-N = 46.5 ppm NO3 => 1.14 g, 21 ppm NO3-N = 93 ppm NO3 => 2.32 g, 42 ppm NO3-N = 186 ppm NO3 => 2.29 g, and 84 ppm NO3-N = 372 ppm NO3 => 2.04 g.


Also the authors in this paper say, that "The critical concentrations for the other species studied (Ceratophyllum demersum, Heteranthera dubia, Elodea occidentalis, Najas flexilis, Zannichelia palustris) were approximately the same as the values for V. americana."


So the unlimiting N concentration for Vallisneria americana (and other species studied) is actually ~93 ppm NO3 (not 21 ppm as you [Tom] say)! So it seems to me that the Estimative index method is all based on a wrong assumption, and incorrect interpretation of the data published in this paper.


20 ppm NO3 => 0.70 g (growth rate)


45 ppm NO3 => 1.14 g


90 ppm NO3 => 2.32 g


190 ppm NO3 => 2.29 g


370 ppm NO3 => 2.04 g


This means that the growth rate was increasing until 90 ppm NO3 was used. At higher concentrations the growth rate remained nearly the same, and then began to decrease, so the NO3 levels above ~200 ppm seems to cause decrease in growth rates in the studied aquatic plants.


From the above incorrect interpretation of Gerloff & Krombholz data you continue to estimate the PO4 levels for EI method:

PO4 data was also discussed. But no such graph was provided, other than tissue analysis for PO4.Still if one assumes a ratio for PO4, then a 6:1 to 10:1 relationship would suggest about 2ppm or higher for PO4(Conversion from N to NO3O4 is addressed FYI).

But if you used the correct data for NO3 (= 90 ppm NO3 as the unlimiting level), then the PO4 concentration should be 9 ppm (not 2 ppm) at the ratio of 10:1 for NO3O4.


Does anybody else noticed this discrepancy in the arguments/explanation used for the EI method?

View attachment 15095

 

[Dennis Singh]

Red plants it seems is just a balance stabled tank. I myself have increased my dosing of both macros and traces to double this:


K 5.27


N 1.69


NO3 7.50


P 0.42


PO4 1.30


traces


etc


I have premixed liquid fertilizers, so each pump per 10 gallons equals those numbers. I have now been doubling this. I am getting red plants now. Along with water changes and continued dosing. I've always had the planted plus lights, why couldn't I get reds then? I was just trying too hard...Its all about stability, the key to red plants imo. In dosing double the amount than recommended, which are still low ppm levels compared to Barr's, algae is more at bay, and plant growth is much better. No mention on co2 as its always been the same with slight fluctuations...


Not the greatest pics, and yes still algae in the pics

 

[Tom Barr]

This seems to be a crucial argument for setting up the proper nutrient concentrations for Estimative Index method by Tom Barr.


The problem is that in the paper by Gerloff and Krombholz all the values are as NO3-N, not NO3 alone. So when Gerloff and Krombholz say that at 4.2 ppm the plant yield is 0.70 g DW (dry weight), 10.5 ppm => 1.14 g, 21 ppm => 2.32 g etc. it means that if we want to convert these to NO3 values, we need to multiply them by a coeficient of 4.43. So 4.2 ppm NO3-N = 18.6 ppm NO3 which yielded 0.70 g of dry weight, 10.5 ppm NO3-N = 46.5 ppm NO3 => 1.14 g, 21 ppm NO3-N = 93 ppm NO3 => 2.32 g, 42 ppm NO3-N = 186 ppm NO3 => 2.29 g, and 84 ppm NO3-N = 372 ppm NO3 => 2.04 g.


Also the authors in this paper say, that "The critical concentrations for the other species studied (Ceratophyllum demersum, Heteranthera dubia, Elodea occidentalis, Najas flexilis, Zannichelia palustris) were approximately the same as the values for V. americana."


So the unlimiting N concentration for Vallisneria americana (and other species studied) is actually ~93 ppm NO3 (not 21 ppm as you [Tom] say)! So it seems to me that the Estimative index method is all based on a wrong assumption, and incorrect interpretation of the data published in this paper.


20 ppm NO3 => 0.70 g (growth rate)


45 ppm NO3 => 1.14 g


90 ppm NO3 => 2.32 g


190 ppm NO3 => 2.29 g


370 ppm NO3 => 2.04 g


This means that the growth rate was increasing until 90 ppm NO3 was used. At higher concentrations the growth rate remained nearly the same, and then began to decrease, so the NO3 levels above ~200 ppm seems to cause decrease in growth rates in the studied aquatic plants.


From the above incorrect interpretation of Gerloff & Krombholz data you continue to estimate the PO4 levels for EI method:


But if you used the correct data for NO3 (= 90 ppm NO3 as the unlimiting level), then the PO4 concentration should be 9 ppm (not 2 ppm) at the ratio of 10:1 for NO3O4.


Does anybody else noticed this discrepancy in the arguments/explanation used for the EI method?

I knew Paul and we discuss this many years later. I modified a few things and by consensus, we arrived at the EI ranges, those were further adjusted to address more PO4 than what I'd started with in the mid 1990's, which was about roughly a 10:1 ratio. Today, I dose roughly 15ppm/5ppm of PO4 twice a week, this meets all non limiting ranges for every species I have ever grown. The non limiting values you state are for NO3, not N-NO3. That is the source for the confusion. Paul had roughly an 80 ppm+ range for NO3. They did not use CO2............. it was not independent. Most research uses N-NO3, but most hobbyists use NO3. I know and understand this, many do not, and I am entirely likely to NOT make mention of it myself on rare occasion when discussing the 200 or so post/emails a day I often post on various forums and other locations. I also do not feel I am required to make every possible detail and addendum every time I post something. If I am submitting a paper, for publication, okay...........but I'm not.


If you want to review the literature for ratios of N in aquatic plants, feel free. UF's, UCD's aquatic plant researchers did this and have publicly stated the same ranges I do. I have the notes still. This does not imply what is best for aquatic plant horticulture, only that what is found in nature. I do not have any issues, most folks do not either. There are larger issues and EI is a tool that's easy to understand and makes the ferts independent so they can focus on other factors to improve their horticulture.

 

[Tom Barr]

Red plants it seems is just a balance stabled tank. I myself have increased my dosing of both macros and traces to double this:

K 5.27


N 1.69


NO3 7.50


P 0.42


PO4 1.30


traces


etc


I have premixed liquid fertilizers, so each pump per 10 gallons equals those numbers. I have now been doubling this. I am getting red plants now. Along with water changes and continued dosing. I've always had the planted plus lights, why couldn't I get reds then? I was just trying too hard...Its all about stability, the key to red plants imo. In dosing double the amount than recommended, which are still low ppm levels compared to Barr's, algae is more at bay, and plant growth is much better. No mention on co2 as its always been the same with slight fluctuations...


Not the greatest pics, and yes still algae in the pics

Yes, but is this due to the stability.....or is it due to the dosing?


I have better color development on red pant if I leave it be for a few weeks in a taller tank than my 120(eg, the 180).


Trim frequency and rates of growth play a role in color. As plants get larger and closer to the light, they also have more biomass and grow faster etc.....so they will use more N/P etc, traces etc, and CO2 is harder to mix due to plans blocking current.


It's not always easy to isolate one factor, but it's easier to rule one factor out as dependent.


Think what it is not, rather than what it is.

 

[Marcel G]

The non limiting values you state are for NO3, not N-NO3.

When you look at the original article (or at least at the picture in my previous post) you would see that the data in the table are in NO3-N, not NO3. So when Gerloff & Krombholz say that the critical (non-limiting) concentration for the studied plants is 21 ppm NO3-N, it is the same as if they were saying 93 ppm NO3 (21 x 4.43 = 93). So I don't understand what's wrong with my numbers. I just converted their N (or NO3-N) into NO3 values.

They did not use CO2............. it was not independent.

That's good to know. So under higher CO2 levels the nutrient uptake should be probably even higher.

I also do not feel I am required to make every possible detail and addendum every time I post something.

Of course you're not. But if you use any scientific paper to confirm or validate your own findings, and you seem to interpret the data in a wrong way (considering 21 ppm NO3-N to be 21 ppm NO3), then don't be surprised if someone else is confused.


BTW, I don't care much about ratios; I was just interested in finding out how you came to the EI recommended concentrations.


When you speak about the EI method, you very often say that it's non-limiting. But why most researchers use modified Hoagland's solution (200 ppm NO3 [partly as NH4], 50 ppm K, 20 ppm PO4 etc.) when studying aquatic plants? Do they not know that non-limiting levels are much lower (like EI claims)? I just try to understand it. Sorry if my comments or questions annoys you.

 

[Dennis Singh]

Yes, but is this due to the stability.....or is it due to the dosing?


I have better color development on red pant if I leave it be for a few weeks in a taller tank than my 120(eg, the 180).


Trim frequency and rates of growth play a role in color. As plants get larger and closer to the light, they also have more biomass and grow faster etc.....so they will use more N/P etc, traces etc, and CO2 is harder to mix due to plans blocking current.


It's not always easy to isolate one factor, but it's easier to rule one factor out as dependent.


Think what it is not, rather than what it is.

I guess it is the dosing, but I have to add that water changes too which I've been not on top till recently are to credit too. I've been doing the 2x dosing for a little bit now, and to add the water changes helps a ton.

 

[Dennis Singh]

Sorry if my comments or questions annoys you.

I highly doubt it, good debate started, plus doesn't seem so easy to get under skin

 

[Tom Barr]

It would be N-NO3..........not NO3 in reference to the paper. And even if I did state that, it would be WRONG, anyone that asked, they and myself would get __corrected__.


Many have stated that higher NO3 ppm's causes stunting/reduced growth, this paper suggest otherwise. It also suggest that EI might be __under dosing__ if you want non limiting growth(at least for V. americana). Many have claimed higher NO3 causes stunting though and many blame EI. Paul himself and others have noted a 1/5th solution of modified hogland's seemed to offer the best growth. You can search for those citations for usage with aquatic plants. Hoagland's adds NH4 to it though. Can folks add more KNO3? Sure, but it's not likely they are anywhere near the ranges that strongly limit. EI is pretty rich overall and aquatic plants do not have the same demands as many terrestrial plants.


Generally:


C range is optimal.


B range is likely where, at least if you used their growth chamber parameters, EI would fall for NO3. Maybe 70-80% with fish loads.


Most other methods, would be at the A range.

Note; Concentration in dry matter and fert ppm's in solution are roughly the equivalent for this discussion.


I've added more than the rates I've suggested, about 3X more. I've gone to 160 ppm NO3. Did I see more growth? Not that I could tell visually. Those dosing rates were short term, Paul's test was 8 week's long I think. At 30 ppm of NO3 a week and perhaps 5-8 ppm as NH4 from fish/shrimp/snails etc, I see few effects that are associated with limitations. This is about = to roughly 50-60 ppm of NO3 a week if you account for NH4 fraction.


But maybe they need to add more. Paul did not think so. Good luck trying to tell folks to add more than EI however. You would be the lone person arguing in favor of that.


You can certainly try it.I had diminishing returns beyond 20-30 ppm ranges dosed 2x a week. Doubling that did not show any negative responses. So 15 ppm seems about right for most cases, but for some tanks, maybe more would help, I do not suggest or state it does not. But "non limiting" might be an incorrect term if you use this paper with V americana when discussing EI. It is much LESS limiting than other aquarist methods.


Try adding that much KNO3 for 2-3 months.That would be 3 table spoons a week of KNO3 for my 180 Gallon.


You'd also need to convince the fish folks that it is okay for their fish and shrimp etc. Another tough sell.


I doubt you can argue to hobbyists to add more than EI.