The objective of this study, conducted in a completely randomized block design at a new banana plantation at EARTH University, Costa Rica, was to evaluate the effect of natural sources of fertilization in the cultivation of bananas. Each block was planted with banana (Musa AAA cv “Williams”) as the main crop, cratylia (Cratylia argentea) as a bank of nutrients, and poró (Erythrina berteroana) for the anchorage of the plants. Prior to seeding, dolomite lime, phosphate rock and EM-compost were applied to all plots. Mucuna ash (Stizolobium aterrimum) was planted as a ground cover to prevent the growth of weeds. In the treatments, the natural sources of nitrogen were EM-compost and a commercial product of enriched poultry manure, and for potassium, K₂SO₄ and K₂SO₄ + MgSO₄ mix were used. The annual program of fertilization per hectare was 300 kg of N and 450 kg of K₂O. During the first five months of cultivation, the contribution of dry matter from the pruning of poró and cratylia was 0.33 Mg/ha. The growth of the plants was monitored and after five months, there were no significant differences between treatments for the variables studied: plant height, leaf emergence, and severity of incidence of black leaf streak (Mycosphaerella fijiensis). The compost plus K₂SO₄ treatment was the most economical, US$ 1,190/year, while the ABIMGRA and Kmag treatment was the most expensive, US$ 2,366/year.