Cheap Organic Phos Sources= None. The "cheapest" is soft rock phosphate, but is only a 0-3-0. Basically, you get the amount of Phos you pay for. Higher grade (%), higher cost. Fish Bone meal (Dr. Earth) is great, as it also contains a lot of micronutrients.
Cheap Synthetic = lots.
For a smaller garden, I would spring for a $30 bucket of 0-8-1 guano by Earth Juice. Indonesian guano from Sunleaves is great, so is Vital's 0-9-0.
There are lot's of Nitrogen sources, including fish water....., but your plants will thrive more with some substantial food. In general, I will use a 8-4-4 guano mixed in to my soil to start the run. Then a week before I flip, I top dress with a 7-7-2. Then 3 weeks into flower I top dress 0-9-0, and again 0-9-0 3 weeks later. All of this is watered in with A.A.C.T..
If you want to keep it super simple, cheap-ish, and organic, just give them Dr.Earth's 4-4-4 all the way through.
As far as boiling banana peels and nut husks to flower.......good luck with that
I would like to hear the reasoning behind that. I have several tea recipes on my site.
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