Taylor,
Have you seen this link yet?
http://www.bananas.org/wiki/Info:Fertilizer
Basically, the commonly accepted breakdown of what the NPK numbers mean is:
- Nitrogen (N) is for foliage/vegetation (grass uses tons of N)
- Phosphate (P) is for roots and flowering (starter fertilizers are usually high in this number)
- Potassium (K) is for fruiting
As for what ratio is best for bananas, that is somewhat subjective and there are tons of opinions on this as you can see from the Wikipedia entry here. I use a balanced fertilizer (meaning all 3 numbers are equal or very similar) because bananas generally seem to do fine on this and it is relatively easy to find and usually cheaper than other stuff marketed for specific uses. BTW I did a search and Vigoro makes a 17-17-17 slow release to compete with Osmocote.
Many people prefer a higher potassium ratio since banana plants consist of more potassium than N and P. 6-2-12 is a popular ratio given this logic and if I could easily and cheaply find this I would use it too. The blends that Going Bananas and Stokes Tropicals are all about this ratio.
Finding something along the lines of 10-5-10 (like the Jobes) or 10-8-10 (I've seen this for Palm fertilizers) would all work too since Phosphorus is generally considered the least important # for bananas. Vigoro makes an 8-4-8 slow release palm food which is another possibility.
The one thing I think is overlooked is the magnesium content. IMO I think most fertilizers are lacking this but this is easily supplemented using Epsom Salt.
As for your question about what you should do with what you have... personally I do not like to use fertilizers that have high N ratios like what you have (24-8-16 and such) unless all you care about is the foliage (maybe on a Basjoo or something.) This also includes the use of Fish emulsion 5-1-1 and such. If it were me I'd just return it and get something balanced.
Laurence