Do not worry so much about ratios, there's never been ANY evidence that it holds weight unless you get to limiting levels.
In other words, 20ppm of NO3 and 20ppm of PO4 are 1:1 ratio, but neither are limiting, likewise, 50ppm of NO3 and 2ppm of PO4 is not either..............
So there's a difference of 25X, and yet neither case has any limitations if those ppm's remain constant.
So it's not the ratio, rather, the individual absolute ppm's, see liebig's law of the minimum.
If every nutrient is non limiting, then CO2/light are limiting growth rate/s.
If that are saturation points as well, then metabolic functioning of the plant is the limitation.
Stay away from the Redfield ratio, it causes a lot more trouble and is misused more than any other parameter in aquatic ecology. Even within algae is causes lots of issue since every one likes to refer to it, and yet if you look at ratios and optima for varous algae species, they are really quite different from the RR.
Same for plants and same for freshwater algae.
You cannot be so broad in such assumptions.
RR might help someone grow plants better than say someone who is not adding any PO4, but that is not due to the RR, it's due to the limiting factor(Liebig applies here, not Redfield).
This guy does not understand this and muck it up even further by assumign mass ratios are the same as atomic ratios:
Charles Buddendorf, seems he finally added a calculator that has the mass differences included, for a long time there was no difference between the atomic and mass ratios
Good to see he finally changed it a few years later.
Still, we can plug some ppm's in and see there's no risk of the various algal claims there either.
Ratios can vary over a much wider range than the RR.
That is something we can consistently demonstrate.
This would suggest that it's not the ratio, rather, the absolute ppm of each individual nutrient.
This goes back to agriculture and Liebig, since aquatic plants are plants after all, and we grow them.............
Just because they are underwater does not change anything.
Inducement of algae is an entirely different case and the RR is not going to limit algae, it might limit plant growth if you reduce it down.
After a long while and at a much lower ppm, it will eventually lower and limit algal growth, but plants will stop growing long before that.
Generalizing too much about
all algae and about
all plants is oversimplifying things. Each species has it's own set of optima and cues, germination signals, ecological niche that it is best suited to compete in.
We can take some average, but simply adding non limiting levels for all plants addresses that. So all we need to do horticulturally is find the min upper bound for each nutrient with the other nutrients set as independent/non limiting.
Then you have a simple easy to target range for growing all aquatic plants.
Curiously, algae do not grow when this occurs.
We can induce algae with altering those ranges, really restricting plant growth.
But is this due to a decline in plant health/growth, or some other cue that algae use to sporulate and recruitment starts?
What causes the algae to germinate from spores to adults/noxious phases?
RR does not explain that at all where aquatic plants are present, not in nature not in aquariums.
It can be used to describe trends in open ocean systems, but with sediments and sources other than the water column, things are not nearly as simple.
I'd just suggest to stay away from it.
Regards,
Tom Barr
