Bananas like a rich soil, full of organic matter. Good drainage and plenty of water. They grow when the soil is warm and like a mulch to keep a consistent soil temperature and moisture level.
Fertilise with a good layer of compost and/or well rotted manure, preferably dug into the soil. Or use a high nitrogen fert like chicken manure pellets until they start fruit production when they like a side dressing of potash.
You could also give them a liquid feed to give them a jump start. Make sure they have enough water though or they won't do much regardless.

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The secret is the soil.