Potassium bioaccumulator plants in the Pacific Northwest

I'm reading Steve Solomon's book "Growing Vegetables West of the Cascades".  I'm in the southern end of the Willamette Valley.
He says our soils are unbalanced---with too much potassium.  Apparently, I've been making my situation even worse by using the native grass hay in my compost.  And adding comfrey---a bioaccumulator for potassium..
Would it work to plant lots more comfrey and totally remove the biomass from the system?
Any other ideas?

I recommend building soil health using wood chips, leaves, etc. first.

I recommend Dr Bryant Redhawk's Soil Series:

https://permies.com/wiki/redhawk-soil

These:

https://permies.com/t/63914/Soil

https://permies.com/t/123928/Growing-Plants-builds-soil-health

https://permies.com/t/75940/Redhawk-methods-making-biodynamic-preparations

Hi Rebecca, Are you noticing a problem with your vegetables?

What is the other side of the balance; which elements does Mr Solomon suggest you have too little of?

No soil is perfect. Honestly, being in a valley with a Mediterranean climate is almost the best situation for growing food, given that you have irrigation when needed. Have you done a soil test to see how unbalanced of various base ions, i.e. the ratio of Ca/K/Mg? If you don't see deficiency symptoms, you probably don't have to worry about it.

I'm 74.  I've gardened for many years---in many soil and climate types.  This current situation has me baffled.
This is my 5th summer at this location.  I moved from Coastal Oregon with it's sand.  My "garden" was 4 and 5 gallon buckets and some 4'x4' raised beds.  I had a lot of wonderful help moving and was able to bring much of it with me.  Everything that first summer of re-establishing the beds looked normal.  The next year, plants struggled.  I put it down to the damage done by a mole---air pruning with it's tunnels.  It took me a month to trap it.  The next year, I dug around to collapse the tunnels.  Plants still struggled.
I have 4 cubic-yard compost bins.  One is always being emptied, another being filled and two decomposing.  I had two tiered worm farms, but the moles kept invading to eat the worms. I now have a worm box.
I have a composting toilet.  3-4 5 gallon bucket contents go into each bin.  I thought the urine might be causing a salt build up---even with 40" of rain a winter....  So I quit adding it, although it hasn't caused any problems with other gardens that I know of..
There are many oak trees here and I wondered if the leaves weren't great for the bins because of tannin.  The grass growing under the trees is not lush.I  switched to local grass hay for my carbon source.
I don't have a car and order many things online.  The cardboard goes into the bins.
I first read the Solomon book when I moved to OR many years ago, but didn't register the K info.  I rented from a lady with goats and I remember she bought alfalfa from the eastern part of the state, because it was necessary for milk production---vs buying local grass hay.  So, I knew about the deficiencies of the hay, but didn't consider it could impact my gardening.  She also supplemented with Selenium.
I don't believe in the usefulness of soil teats; they say nothing about availability of plant nutrients.  My neighbor's tomatoes don't have cat faces. So Ca is fine....
Having dealt with symphylans in the past, I've developed the practice of starting seedlings off in 4x4 pots with good soil.  It hasn't been enough to produce the results you would expect after transplanting.
I've ordered some liquid fertilizer that is 5-5-1.  My next experiment.

I would suggest a plant tissue analysis, very affordable and will show you what is normal, deficient or excessive. Would not be without this test, is part of my fertility decision making.


https://midwestlabs.com/agronomy

Plant Tissue Analysis Nitrogen, Sulfur, Phosphorus, Potassium, Magnesium, Calcium, Sodium, Iron, Manganese, Copper, Boron, Zinc Call for sample size * Results, 3 Days $24.20

Moving from sandy coastal soil to a valley with heavier ground is a big shift. The tissue test suggestion is a good one, though it sounds like you've already got enough experience to know when something's off just from how the plants look. Moles causing disruption in the early years would have thrown things off too, compaction and drainage-wise. Sometimes it's worth just trialling one bed with a different approach and watching closely before going all in on a fix.

Trapping the rodent was my first experience with a mole; it's different than the pocket gophers I trapped as a kid in MN.  The boards of the raised beds make the effort so difficult, because of the way the jaws have to be positioned to work.
Steve Solomon started Territorial Seed Co. over by Eugene.  He states the PNW soil, because of our pattern of heavy winter rainfall, is deficient in everything but potassium.  In the book, he has a recipe for building a supplement.  I don't have any outbuilding to store the materials = I've ordered some from a company that still formulates it.  
After reading the book, I'm pretty sure my problems are due to use of grass hay in building the compost piles---and even using grass clippings for mulch on the beds.  I wasmaking high potassium levels even higher for the plants.
I wondered if there was a way to trap the potassium and remove it, thus lowering numbers., But it's probably a better approach to make a concerted effort to raise everything else up.  And no more grass.