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
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.
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
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.
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
Paulo Bessa wrote:How about phosphorus?
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.