Backyard Aquaponics
A place to discuss aquaponics

By all accounts the 2 things that aquaponics systems are prone to become deficient in are iron and potassium. Iron I have covered by the odd addition of chelated iron now and again. As for potassium I am not sure what to do, but I am pretty sure that the plants are starting to show some deficiencies.

Preferably I would like to supplement the system for potassium in some natural way. Does anybody know how one can produce their own potash. Is this just a matter of burning something in particular?? Any other suggestions for potassium addition?

VB what are the signs in your plants of potassium deficiencies. Something is missing in my system too. Corn plants are stripey.

Yes - some of my plants have light patches - a bit like striping. Must dig up that deficiency sign post that Nick did.

Found this on the web about cucumber nutitional deficiencies (see the table). Probably similar for other plants.

BTW, from the description (Scorching and yellowing around the edges of leaves and between the main veins) my silverbeet are showing obvious signs of potassium deficiency. I have also noticed that except for my first crop, things have not grown that well in the aqua system, which I reckon is a result of this deficiency. Lettuce flew the first time, but since then have been pretty ordinary. I will do some searching to find out how to produce some organis potassium (if that is possible).

'Short-term potassium deficiency can be met with liquid manure made from plants that concentrate potash, such as lucerne, comfrey leaves, or bracken fern.'

Looks like I'll have to start trials of using comfrey tea in my system - which I had considerred doing anyway for all the other mineral properties. I wonder if potassium is retained in the ash of slow burned comfrey (burned like charcoal is made). If so - I could get a stockpile to use, much more convenient than using a tea - as comfrey tea tends to be pretty rank, pretty quickly.

Try (How to make potassium by the jolly rodger)google.
Seems to be what you are looking for.

That seems to be how to make potassium nitrate (for bombs and shit). The potssium seems to be added to the recipe by use of the wood ash. The question is how to make a wood ash that is high in potssium - this requires burning of a plant high in potassium.

Here is an interesting link on the subject - I have classic potassium deficiency in my system. My cucumbers are really suffering
Potassium deficency

This product may be helpful

product
I have sent them an email asking for further specs.

Muzza

Worm castings from a bin with a high input of potassium rich plant matter may contain some of it. A rockdust product added to the worm bin could add in many other minerals for additional balance, while providing worms with grinding matter.
There are essentially "organic" sources of potash avaliable on the market. Thats where I would start if I needed to go into fertilizing on that level.

Worms are more fun though....

Good link VB, I am wondering if some of these deficiencies may be overcome as the system matures over time, wonder if Joel or others have noticed any slow down of growth. As yet, my stuff is still growing fast

Be warned that comfrey is indestructible and weedy once planted, so plant it somewhere out of the way and not likely to spread into bushland. VB is right, you can't 'make' potassium like you can 'make' nitrogen, there are no practical backyard methods to transmute metals.

Hi guys, some info which pertains to hydro growing and potassium... have seen these symptoms mirrored in soil gardening.



Looking through my hydro notes for ways to up potassium uptake... certainly appears uptake improves when pH tends toward alkaline...
and suffers with salinity, so anyone who's salted may just have to wait it out a while or maybe "flush" the system with a water change.

Should have added...

High Potassium will result in Calcium deficiency.

Presume the potential for pH swing as well

I've been aware for a long time that some animal manures contain more potassium than others - pig manure is very low in K, but I have an abundance of it and no access to cow- or chicken manure, so the simple solution is to add potash. (N = plant growth, P = root growth and seed setting, K = fruit growth.)

I've often wondered if by changing the diet of the animal whether the nutrient mix of the manure can be altered. Bananas, spinach and wheat-germ are among the potassium-rich foods, and if these were made available to the fish in some form acceptable to them, would this increase the K content of the manure ?

I'm not quite game enough to toss a bit of potash into the pond, I could have some ungrateful fish.

Sardines, pilchards and potato crisps are also high in K - could be some interesting mixes of fish food coming out of my blender soon !

Spinach could be the first experiment - just chuck it in the pond and see how they go for it.