I will not get into the issue with the difference between the mass ratio, which is what is used, versus what Redfield actually shown in his paper based on averages of marine phytoplankton, it was atomic ratios, atoms, not mass(eg ppm etc). So 106 carbon atoms to 16 nitrogen atoms to 1 P atoms and so forth. To convert to mass, you need to factor in molar weights, N/P will be 16N's* 14 g/mol/ 1P* 30.97 g/mol= 7.2 for a ratio for N
for algae based on weight or about 10:1 for ratio for NO3/PO4. Likely N is higher in practice since NH4 is also used by algae and plants and that is rarely detected.
That aside, some seem to have fallen for the trap that because they went from bad to okay or even good, that the reasons must be due to the claim that it is the ratio, not that they simply have started to dose a strongly limiting nutrient.
The concept of limiting growth is based on Liebig's law of the minimum. Not ratios...........
Algae are not limited based ion ratios either. They are limited based on concentration, and light and CO2 play significant factors also.
Plants are doing better because they are not as limited now, not because of a "ratio".
You can have success but attribute it to the wrong reason and make the entirely incorrect conclusion.
That was what was done with PMDD in years past with PO4.
Same type of thing here and the same issue with most methods.
They take great liberty when it comes to explaining their results in the conclusion.
Even if the results do not support them :roll:
I can have a ratio of 5ppom of PO5 and 5ppm of NO3 and still do pretty well.
Likewise, I can have 30ppm of NO3 and 1 ppm of PO4 and do well also.
Ratios are 1:1 and 30:1, far outside the RR, and yet no algae of any kind...........
So what explains these observations?
Simple: in both cases the tanks' plants are not limit for N or P.
The ratio with 1:1 will become limited faster for N, but at this ratio, it explains nothing. It's only when the nutrient become limiting, that growth is affected, so anything above a limiting value, just like Liebig states............is what determines growth.
Plant growth, not limiting algae(they are not limited in my ratio systems either, which is a wider range than RR), is what the issue is.
Generally, most have low light also, so that means/implies even more flexibility when it coems to dosing and ratios/lower values for limiting, easier CO2 dosing etc.
I also have not seen any of the so called algae issues based solely on the nutrient ratios as claimed either.
But then again, my CO2 levels are in good shape and demand for CO2 is not influenced by low PO4 etc. They seem to have non independent factors occuring(eg poor CO2 which is being propped up by semi limited PO4 and low light).
When you add more light and good CO2, these same results are no longer present and the model does not fulfill the logic: a "ratio" some how limits and controls algae and helps plants grow better.
If you I have a ratio of 0.01 PO4 and NO3 of 0.16, I can promise you, plants will not do well.
They are limited and the ratio falls apart.
Regards,
Tom Barr
/www4.carleton.ca/jmc/cnews/07032008/n4.shtml
