Old NO3 growth optimal test from Paul Krombholz

[Marcel G]

First of all, I'm not telling or suggesting to use more nutrients then EI recommends. I was only pointing out your error in confusing N (or NO3-N) with NO3 in your first post (and probably in designing your EI method as well). I know very well that in the Gerloff & Krombholz study they used diluted Hoagland's solution (200 ppm NO3, 50 ppm K, 20 ppm PO4, 40 ppm Ca, 10 ppm Mg, 0.4-0.8 ppm Fe etc.). This diluted nutrient solution is used very often for growing aquatic plants without a substrate media in hydroponics, so it's quite a standard. You know very well, that very often you say EI is supplying a non-limiting nutrient levels. So I wanted to point out, that it's simply not true. The non-limiting values would be the modified Hoagland's ones (200 ppm NO3, 20 ppm PO4 etc.), but not EI (30 ppm NO3, 3 ppm PO4). Again, I'm not telling we should use Hoagland's modified soup for growing our plants ... I just say, "EI is not non-limiting" (as you do say). So although it seems you based your EI metod on a wrong interpretation of Gerloff & Krombholz data, still I think the EI method is one of the best fertilizer methods suited for growing aquatic plants in our tanks, and if we combine it with any nutrient rich substrate, then we can supply our plants with nearly optimal nutrient levels for a maximum growth rates. I would like to point out also that according to my tests (and I believe I'm not the first one to find this) the plants use up only a relatively small fraction of nutrients from the external medium per week. So under 30 ppm NO3 in water column they may use up maybe 5-7 ppm NO3 per week, while under 10 ppm NO3, they will use up only 3-4 ppm NO3 per week under strong light and high CO2. So this seems to be another argument for why to use higher nutrient concentrations (like EI suggests) ... in case you want your plants to grow really fast.


PS: I did not find any reference in Gerloff & Krombholz paper (nor in the Hutchinson's book) as to how long did the test take.

 

[Tom Barr]

First of all, I'm not telling or suggesting to use more nutrients then EI recommends. I was only pointing out your error in confusing N (or NO3-N) with NO3 in your first post (and probably in designing your EI method as well). I know very well that in the Gerloff & Krombholz study they used diluted Hoagland's solution (200 ppm NO3, 50 ppm K, 20 ppm PO4, 40 ppm Ca, 10 ppm Mg, 0.4-0.8 ppm Fe etc.). This diluted nutrient solution is used very often for growing aquatic plants without a substrate media in hydroponics, so it's quite a standard. You know very well, that very often you say EI is supplying a non-limiting nutrient levels. So I wanted to point out, that it's simply not true. The non-limiting values would be the modified Hoagland's ones (200 ppm NO3, 20 ppm PO4 etc.), but not EI (30 ppm NO3, 3 ppm PO4). Again, I'm not telling we should use Hoagland's modified soup for growing our plants ... I just say, "EI is not non-limiting" (as you do say). So although it seems you based your EI metod on a wrong interpretation of Gerloff & Krombholz data, still I think the EI method is one of the best fertilizer methods suited for growing aquatic plants in our tanks, and if we combine it with any nutrient rich substrate, then we can supply our plants with nearly optimal nutrient levels for a maximum growth rates. I would like to point out also that according to my tests (and I believe I'm not the first one to find this) the plants use up only a relatively small fraction of nutrients from the external medium per week. So under 30 ppm NO3 in water column they may use up maybe 5-7 ppm NO3 per week, while under 10 ppm NO3, they will use up only 3-4 ppm NO3 per week under strong light and high CO2. So this seems to be another argument for why to use higher nutrient concentrations (like EI suggests) ... in case you want your plants to grow really fast.
PS: I did not find any reference in Gerloff & Krombholz paper (nor in the Hutchinson's book) as to how long did the test take.

__Thanks__, I fixed it in the original post, I was trying to figure out where the issue was(original post). Once I found that, I went and fixed/edited it. Thanks for catching that.


Another example of this is with the Bowes, Haller Van paper on Hydrilla and the best rates of growth and uptake % for various amounts of Fe as ETDA Fe with Hydrilla.


They suggested 8 ppm for the optimal rate of growth and 6 ppm for the highest mineral tissue content.


http://www.sciencedirect.com/science/article/pii/0304377077900390


These papers both suggest a higher rate of growth for NON limiting values.


I think this really brings into question EI's claim of "non limitation".


That I have stated often. I do not think I should really though.


Still, how many folks have dosed 6-8 ppm of Fe?


Or 100 ppm of NO3?


I could say that EI is (much) LESS limiting than most other methods.


That would be a much more accurate statement.


But as you suggest, adding the RICH sediment + the EI to the water column.........I think we can or at least strongly suggest, we are in the target ranges of non limitation with a rich sediment source + a rich water column, without having to add 100-200 ppm NO3 to the water column. I would suggest I HAVE seen evidence of that. I consistently over time have had better growth and development of aquatic plants using rich sediments and rich water column.


Thanks again.

 

[Tom Barr]

Another question also comes up often in argument to EI: At lower ppm's of N/P, growth is slowed, which for some aquarist, means less gardening or work/labor, thus they justify using less and limiting the nutrients in order to reduce labor.


I've argued that using less light or simply better plant species choices, more appropriate planting, more hardscape etc would meet that goal in a better way.


For the more experienced plant aquarist, it is a viable method however, but care is needed to do it and most new folks really will not do so well.


Likewise, if you strongly limit a nutrient, you will limit CO2 demand, which can help folks that have had trouble managing CO2, but have just given up on it.


I view that as a "crutch" to not learn more about good CO2 fertilization.


Once an aquarist masters and knows what good CO2 looks like and is good with setting up multiple tanks with excellent CO2 management, then they have arrived.


Then you can be all over the place with ferts.


Plants still grow as long as there is something, but how they grow might be another matter, or the species types etc.


Another point: Aesthetics of how the plants look and grow versus non limiting conditions are two different goals hobbyists have versus a researcher looking at non limitation.


I'll likely bring these issues up at the AGA meeting this April.

 

[Tom Barr]

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

He was correct, I went back and edited the error.


Then found more support against non limiting values for Fe.

 

[Marcel G]

But as you suggest, adding the RICH sediment + the EI to the water column.........I think we can or at least strongly suggest, we are in the target ranges of non limitation with a rich sediment source + a rich water column, without having to add 100-200 ppm NO3 to the water column. I would suggest I HAVE seen evidence of that. I consistently over time have had better growth and development of aquatic plants using rich sediments and rich water column. Thanks again.

Yes, if you use nutrient rich substrate together with EI + some fish waste, then you could be very close to the non-limiting nutrient values ... and even if you were not as close, the values you have in such a tank should be good enough for a good plant growth.

 

[UDGags]

Great conversation, I had one simple question. On average how long does it take a plant to adapt to the concentration changes it might see? Say if the water column was at 20ppm and then all of a sudden one upped it to 200ppm. Days? Weeks?

 

[Tom Barr]

You're welcome! This is exactly what I like on it => if you use nutrient rich substrate together with EI + some fish waste, then you should be very close to the non-limiting nutrient values ... and even if you were not as close, the values you have in such a tank should be good for excellent plant growth.


I have to say, that at first, I was enthusiastic about EI method, then I began to highly doubt about it, but finally (after I came to better understand it's background and came to know what non-limiting concentrations are) I like it again.

Well, as hobbyists, we also can see that and there's support within the hobby for this but the 6 ppm of Fe? I do not think we are going to talk any hobbyist into that


But what you suggested offers a rational support for why adding a rich sediment is wise.


As the ADA AS ages, the N content drops, but not for the other nutrients. Growth does decline also. So...........there is support for the higher N levels also I would argue.


I often state that rich sediment + rich water column= synergistic= back up, redundancy, better. But this offers __more support__ than just observations. And a method to do so without suggesting to hobbyists to add 100 ppm of NO3. There's likely that much or more as NH4 in soils...........but they do not see it in the water, they do not care it seems.

 

[Tug]

This would explain my experience, less light with CO2 (stability), plants adjust to the limitation of their environment. With ADA AS (read as Kleenex) and/or EI (less limiting) water column dosing, landscapes are easier to maintain at constant levels, over a longer time. Now, pulsing higher levels (2-5X daily EI) every other day makes more sense for some/most plants. Well, that and providing for a better soil and it opens up a hole range of possibilities for CO2.