Agronomic efficiency of different nitrogen sources for banana production and fruit quality

ABSTRACT To define a suitable N fertilization management strategy to improve the productivity and economic performance of banana (Cavendish subgroup) production, technical criteria are needed to select N sources and establish dose rates. This study aimed to evaluate the effects of different forms of N, specifically amidic (urea and urea + NBPT), ammoniacal (ammonium sulfate), and nitric (calcium nitrate), on the nutritional status of banana plants, the severity of Sigatoka complex, and fruit productivity and quality. Profitability associated with the use of different N sources was also assessed. Treatments were conducted according to the factorial combination (3 × 4 × 2) + 1, considering three N sources (urea treated with NBPT, ammonium sulfate, and calcium nitrate), four N application rates (0, 75, 150, and 225 kg ha -1 ), two production cycles (second and third cycles), and a control treatment (plain urea applied at 150 kg ha -1 ). Fertilization led to soil acidification in the second cycle, with no increase in foliar N content associated with the N sources or doses, indicating that the N supply was due to the residual effect of previous fertilizations and to the mineralization of organic matter and plant remnants. Urea, urea treated with NBPT, ammonium sulfate, and calcium nitrate did not differ in banana plant nutrition, Sigatoka severity, or fruit production and quality. Higher N doses increased production in the third cycle, indicating that the recommended dose for high productivity was an underestimation. Nitrogen fertilizer that provided the best economic return was urea, followed by urea treated with urease inhibitor (NBPT), ammonium sulfate, and calcium nitrate. Fertilizer cost per unit of N was found to be a major factor determining the expense of fertilization and the profitability of banana production.