A beginner's question, I'm sure.

In a crop setting, it seems that we can fix about all of the nitrogen we care to, and phosphorous (as far as I know) is in decent abundance in most soils and can be accessed from subsoil using various techniques...but how do people replace the potassium that comes out of the system?? I've heard that ash is decent, but my soils are already at pH ~7.8

Thanks!

I think planting Borage (annual) or Comfrey (perennial) would work well.
You could also create a liquid fertilizer from the above plants and/or others which would give good potassium results. Kelp or seaweed if you live near a sea has potassium.

Compost and manure also if you have it.

I'm sketchy on Ash. I've never used it and I think dosage is really important. Plus it creates short-term ph modifications that might not be very useful in the long run.

best,
William

Toby Hemenway gives an extensive list of dynamic accumulators in Gaia's Garden. He does list borage and comfrey but a host of other plants such as buckwheat, carrot leaves, chives, dandelion, etc. Unfortunatelly, there are no indications as to whether the plant is good at accumulating potassium (or any other nutrients). My guess is that if you have a diverse flora in your garden, the minerals will get into ballance eventually.

Here's a listing of dynamic accumulators: http://oregonbd.org/Class/accum.htm

Most K is in primary minerals in most soils except silica sand at 30,000 to 50,000 kg per acre in the top 6 inches. It leaches and accumulates in biomass so biomass export is the worst for flow off site (silage). Manure provides import (animals concentrate). Next to minerals, wood provides a reserve, liberated in wood ash. Seaweed is high. Granite dust also high. I suspect that where a vegetation is fully engaging the soil profile, and biomass exports are limited you may be able to mine soil for K at a rate that replaces loss. If you are sending biomass out you may need biomass in. With the large soil reserves, using deep rooted K accumulators makes good sense as a realistic strategy. (Mostly from Brady and Weil). If you have sand you have to be even more careful.

Seaweed is a great source of potassium, and as a bonus you get loads of other minerals.
I don't wash seaweed, but my soil is extremely sandy, so there's no salt buildup. Plant-damaging sodium chloride is only a small fraction of valuable sea salts anyway.
I don't use ash as my ph is at the upper edge of good, and ashes are very alkaline

What about using hugelkulture to slowly liberate potassium from trees and avoid using pH altering ashes? Couldn't that be a solution for sandy soils with less K?

Great information - thanks everyone! Since I live 100s of miles from the nearest ocean, seaweed doesn't seem like the best permaculture solution, but I appreciate the info on the dynamic accumulators.

Tyler Cullender wrote:Great information - thanks everyone! Since I live 100s of miles from the nearest ocean, seaweed doesn't seem like the best permaculture solution, but I appreciate the info on the dynamic accumulators.

So do I!

You asked the right question.

Holmgren doesn't like heavy/sheet/lasagna mulching precisely because in the long term it can lead to potassium deficiencies. edit: K buildup.

So you plant comfrey, do some liquid plant fertilizers high in potassium, and be done with it.

ps-distance from ocean: you can buy kelp in a bag, but yeah, not a good solution for other reasons (salt, using external inputs, money). Better to read the Gaia's Garden appendix for dynamic accumulators of potassium and plant those.
William

Rick Larson wrote:

Tyler Cullender wrote:Great information - thanks everyone! Since I live 100s of miles from the nearest ocean, seaweed doesn't seem like the best permaculture solution, but I appreciate the info on the dynamic accumulators.

So do I!

You asked the right question.

I third that motion. Also, I really expected alfalfa to have more value as a dynamic accumulator than it apparently does.

The most complete chop&drop combination seems to be something like:
Coltsfoot + Comfrey + Dandelions + Lamb's Quarters + Vetch

How about phosphorus?

Any ideas of what biodynamic accumulators have it?

Paulo Bessa wrote:How about phosphorus?

https://phytochem.nal.usda.gov/phytochem/chemicals/show/14516?qlookup=phosphorus&offset=0&max=20&et=

Steve Solomon seemed to think that an ordinary soil supplied with organic matter would have too much potassium, not too little, also that it was less important then phosphorus and other minerals for health.

I guess it would depend on the type of soil. But according to him, many if not most soils still have plenty of potassium long after all the other nutrients have washed away.

Phosphorus on the other hand is in global short supply and is non-renewable; it is heading for the ocean at an alarming rate.