If this is for fertilizing your bananas, I'd go with the Potassium Nitrate, David. Recently bought some off Amazon for my orchids, as we have well water here that is high in Phosphorus so it's good not to add any more of that with the fertilizer. My orchid book even said "if you buy it at farm supply in a 50lb. bag, it's very economical and you can use it on your bananas too".
I only bought a pound, since I'm not growing bananas at the moment.
