edwmax

A Banana plant needs 1 lb of nitrogen and 1.5 lb of potash per growing season (aka: year).

If you used 10-10-10 fertilizer, then for 1 lb of nitrogen you would need:
1lb / .10 = 10 lbs of fertilizer.

BUT, 10 lbs of 10-10-10 will only furnish 1 lb of potash (K). ... 10 lb X .10 = 1 lb Therefore, a supplement of potash is needed to furnish additional 1/2 lb of potash (K) for a total of 1 1/2 lbs. ... exam: potassium sulfate (0-0-52) => 1/2 lb / 52% = .96 lbs supplement.

So if the fertilizer is formulated to furnish the TOTAL needs of the plant, a supplement would NOT be required.

That is the basics. So now to your question, Banana Fuel 15-5-30.

5 lbs of Banana Fuel will supply 1.5 lbs of potash (K) ..... 5 lb X .30 = 1.5 lb
BUT, 5 lbs of Banana Fuel will only supply 3/4 lbs of Nitrogen (N) .... 5 lb X .15 = .75 lb Therefore, a supplement of 1/4 lb of nitrogen is needed.

Banana Fuel was designed for the Tropics where the environment furnished the 1/4 lb of Nitrogen by vegetation decay. ... Here in the US unless you use lots of compost with your banana plants then 1/4 lb of nitrogen should be furnished with a nitrogen supplement or a complete fertilizer formulated for growing bananas such as Fruit Fuel (16-8-24) may be used.

Fruit Fuel (16-8-24): 1 lb nitrogen / 16% = 6.25 lb fertilizer
6.25 lbs X 24% = 1.5 lbs potash (K) .... no supplement required for N & K

Knowing how to calculate the N-P-K needs of a plant you can adjust the type fertilizer being used to the plant needs and make fertilizer selection based on availability & cost. ... Using a balanced fertilizer 10-10-10 with minors formulated for gardens & vegetables ($10 / 50 lb bag) and a potassium supplement, I can fertilize my banana plants at a cost of $3 per plant for the season.

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