Dry plant tissue analysis published by Edward on his PPS systems put Potassium at 27% by weight. Diana Walstad's book implies a similar number.
I hope someone posts in with an answer for both of us.
If, that is if, they stated that is the dry weight 27% for K+, they are wrong(Diana did not report this BTW in her book).
K+ is typically 1, maybe 2% for aquatic plants. Various aquatic plant species are widely available on line for ppm and % dry weights. See references below.
The person referenced by Diana, Gerloff, has a paper widely available:
The 1975 book is not easy to get a hold of.
8000 mg/kg does not translate to 27% dry weight.
8 g/1000g = 0.8% for critical concentration, and 4.5% for her plant references.
Reddy covers a more review based approach to K+ in aquatic plants.
1% to 8% in one of the highest K+ dry weight aquatic plants.
1-2% is a typical range, and with more N and P, there's more K+ uptake.
If you limit the other factors, like light, CO2 or other nutrients, then it can have a reducing effect on K+ uptake.
20-50ppm are typical ranges of K+, NO3 is often in the 20-50ppm ranges, P at 2-4 ppm ranges for their non limiting growth solutions.
This is typical for EI dosing
EI is suppose to be non limiting for nutrients, only then then can you look at factors independently. This way you have a reference to compare to.
If you limit say CO2 or other nutrients, it makes the results confounding.
Each species will also have their own ranges
of ppm's that's optimal.
Non limiting is somewhat easy to target if you have a community of various species, limiting concentrations in a community of different species will have a lot more competition interactions between different species.
This is much harder to target and find the right range for every species in the tank.
This is also true for light and CO2 as well as nutrients.
So rather than trying to figure heads or tails and all the possible variations, I go higher for CO2/nutrients and find non limiting for the weakest most prissy wimpy plants that are the poorest competitors.
If they do well, then the rest of the strong competitors surely will. This is not unreasonable logic.