Read the info for fertilizer in the forum wiki for more detailed explanation.
Info:Fertilizer - Bananas Wiki
But to answer your question 'How much 46-0-0 to apply?' Nitrogen in this concentration can more easily burn the plant roots if too much is applied. ... Mature banana plant only need 1 lb of nitrogen per year (or growing season). At 46%, only a little more than 2 lbs 'total' (1 lb / 46% = 2.17 lb) is needed for the growing season and this to be divided equally (5 or 6 mths ??) and applied monthly.
My self I just use 10-10-10 garden mix (tomato) fertilizer ($10 per 50 lb). It has the minor elements garden plants & bananas need. Then supplement with potassium sulfate for the extra potassium needed.