The objective of this study was to evaluate the agronomic response of nitrogen and potassium fertilization during the first production cycle of plantain (Musa AAB). The experiment was established in La Fortuna, San Carlos, in the North of Costa Rica, for two consecutive years (2008 and 2009).The study area featured a medium fertility Inceptisol soil formed by alluvial materials. Nitrogen was applied at a ratio of 0, 100, 200 kg of N/ha, while K20 was applied at 0,125, 250 and 375 kg/ha, each year. Sowing was done using Curraré Semi Giant cultivar corms, at a density of 2380 and 2224 plants per hectare, every year. The variables evaluated were pseudostem circumference and height, bunch weight, number of fruits and hands per bunch, and caliber of the central fruit of the second hand. The results portray statistically significant differences at the 100 and 200 kg N/ha doses in all variables, except for the number of hands per bunch in both periods: 2008-2009 and 2009-2010; the best results were obtained for the 2009-2010 period. On the other hand, the application of potassium did not lead to significant responses in the first period, most likely because of a bacterial disease detected at the five months age, however, in 2009-2010 there were significant differences in the length and gauge of the middle fruit of the second hand. It is also possible that an interaction occurred between N and K2O and these two variables, because the greatest length (29.13 cm) and gauge (63.04; 1/32 inch) took place with the highest doses of both. Furthermore, nutrient absorption by the plants was determined, resulting values of 102.6 and 227.8 kg of N and K/ha, respectively.
Keywords: Musa AAB, Curraré plantain, yield in Musa AAB, bunch characteristics of Musa AAB.