Re: Bananas grow smaller each year...
Bananas fertilize the soil in my experience. They support detrivores like no other plants I have ever seen. The soil becomes so rich and full of life I use it as potting soil. Bananas are not tomatoes. I supplement with ash, charcoal, and other potassium sources. I maintain heavy layers of forest mulch and fungus. Isopods, millipedes, and earthworms do the rest. If your bananas are producing fewer and fewer this is common as mats get thicker. Maintain only 3 or 4 plants per mat and keep them mulched and you should return to the good days.