@Emilya and I were having a discussion on FPJs in response to a question I asked her about her dandelion thread, and I thought I would repost some of my (edited) thoughts for those interested in using FPJs in their gardens.
My sources for the table and other info includes the book "The Regenerative Growers Guide to Garden Amendments" by Nigel Palmer.
My conclusion is, that by using a combination of comfrey and horsetail fern (or comfrey and stinging nettle), one can get an even higher level of most of the desirous minerals and nutrients while keeping a relatively lower level of the heavy metals as compared to dandelion. Add ease and quantity of harvest, and comfrey + horsetail fern are going to be my new goto's for the base of my FPJ routine. I'll still use egg shell, LAB, kelp and other things, but these two will be my main supplements. Plus, they can be used as either a soil drench or foliar feed, so they can be applied as often as needed even if it is not watering day. The suggested application rate is 1:1,000. I use 1:750 which works out to 1tsp/Gal.
The combination is high in P and K and Ca and Fe among others. Still not quite as good as a good deep ocean blue fish ferment, but probably more accessible to many, and actually pretty close on most items.
--------------------
The following are the numbers from the table in the back of the book. You'll note that comfrey has a number for "P" that is more than twice that of dandelion, as is "K" as well. Dandelion is higher in things like chlorine, sodium and aluminum, but I guess I would question how much is too much (sodium+chloride =salt of which too much is generally a bad thing).
So, given the numbers, I am switching over to comfrey + horsetail fern, and I planted some Russian Comfrey, the Bocking 14 cultivar, in my garden this spring. Another advantage comfrey has over most of the plants on the list is sheer mass at harvest time. The mass of one comfrey plant can be equal to many dozens of dandelion plants. After reading your thread last summer, I went around my yard collecting dandelions with a dandelion weeder to get the roots as well, and remember it was a lot of work. This summer I expect to harvest 10x as much or more from one comfrey plant, and I'll also have enough to experiment with different methods and combinations. There are 2-3 harvests a year.
The book lists the ppms of 14 different plants from a lab analysis the author had done if memory serves. All of the following numbers are for a brown sugar ferment.
In any event, here you go and apologies in advance for the formatting. I listed a few in another thread and I remember having issues with the columns lining up...
....... Comf....Dand....Nettl.....Hors.......Fish
P......270.8.....128....35.34.......42.1.....836.8
K......1,025.....485.......376......876.5.....1,013
Ca....31.52.....143.......861......358.1.....718.8
Si.......15.4........28......24.6........28.8.......0.29
Fe......2.06.....3.17......1.57........6.74.......2.57
S........8.32.....33.5....70.17......56.79.....127.2
Cl..........80...1,340....1,050.........300.....1,000
Mg...34.15.....53.4.......141......90.92.....105.7
Na......0.58.....3.25......0.55........1.11.....109.3
Al........0.31.....2.51......0.90........1.15.......1.31
B.........0.40.....0.44......1.37........0.22.......0.12
Co.....<0.01.....0.02...<0.02.......<0.01......0.02
Cu.......0.15.....0.18......0.11........0.16.......0.17
Mn......0.65.....1.63......1.18........3.14.......1.23
Mo......0.07.....0.13......0.14........0.03.......0.02
Ni......0.034.....0.01......0.01........0.04.......0.02
Se........0.45.......1.8......1.03........0.30.......0.16
Zn........0.49.....0.56......0.57........0.65.......1.63
So, this table is why I suggested in my initial post that comfrey and nettle are even better than the mighty dandelion, and fermented fish is better than all of them on most measures. It also is why I think combining comfrey and horsetail fern is a great combination without getting too crazy. Two FPJs whose plants are easy to harvest in quantities that are useful even for larger gardens. Comfrey and S.Nettle also would be a good combination. I just happen to have a ton of horsetail fern and no stinging nettle on my property which is why I'm going that route. Plus, the HF is easier to harvest with bare hands. ; )
Anyway, that's the background for my plan for this season. And all thanks to you for getting me started down this path.
----------------
I guess that still leaves the question of what ppms do the plants want and need, but maybe the hydro folks can offer suggestions for that.