"I like to use natural stuff
...
Is there any sense to this line of thinking?"

I use 100% unnatural stuff and do just fine, so no.

"I currently feed them the sludge from my fish pond filter, which contains nitrogen and phosphorus, but no potassium."

How do you know?

Why don't use cow, horse, or chicken manure?

I know because I know what is in my fish and my pond water. I have had poor results from chemical fertilizers in the past. I don't have livestock, nor do I want to transport manure in my family vehicle. Any other potassium sources?

"Any other potassium sources?"

1. Saltpeter

There exists natural potassium nitrate (saltpeter) that is mined from caves. I had a 100 lb. bag from Italy. My source no longer exists, so you will have to locate a source yourself.

2. Greensand - Slow release, also contains silicon and banana plants are about 1% dry weight silicon.

I read that some Louisiana soils require frequent liming. Although Chicago area soils have too much lime, I can tell you from my experience with banana plants potted in soillless mix that occasional fertilization with calcium nitrate does wonders.

go to a feed store. look for Hi-Yield, they have Muriate of potash. a 4 pound bag should cost around $3.29. there may be other companies who produce it. it has a guarenteed analysis of: 0-0-60 of soluble potash.

Thanks for all the info, guys! :) I'll go hunting for the above stuff and see what I can find. Here's to happy nanners!

Wood ashes are a good natural souce of potassium .

Hey!
I use banana peels along with composted manure (we have cattle)..bury one in spring and again mid summer I also use this on my roses. They seem to like it .It's natural and cheap...
Chena

Taffy,You can buy 40 pound bags of composted cow manure for about 2 dollars at any garden center, loews, or home depot. It works wonders and has only a slight odor when you first open the plastic bag, but not after. someone once said, " to grow a great rose, you start with a great cow"

nucci60,
That's funny about the rose and the cow. Out at my grandma's place, an unused cow pasture was taken over by huge rugosa roses. I thought they were great, the pasture owner hated them like kudzu. The hips were beautiful.

My son is starting 4-H in school this year. He wants a rabbit. I want the rabbit poo. I'm not sure how many bunny pellets I'll get for free from this 4-H project, but if its not enough, I can always get a 2nd or 3rd rabbit. Not many pets that a person can look forward to having what comes out the other end. Maybe I'll put the rabbit cage on wheels and roll it around from garden bed to garden bed. Kinda like a chicken tractor, but smaller and quieter.

I'll hopefully get enough for my bananas.... Should I keep fetilizing through fall? Here in central Louisiana, the bananas sometimes never loose their leaves if we have a mild winter. Sometimes they turn brown in November.

Thanks!

Ooooo!!!Taffy.. Be careful with rabbit duty it is HOT and can burn when fresh...BUT let it dry and what a wonderful resource.. Better get more than one..LOL (the same gender... ya know!!!)
Chena