Nitrogen fertilization in banana grown on a highly weathered soil of the humid mountain region of Puerto Rico

Abstract

A 40-month experiment was conducted to re-evaluate the nitrogen fertilization recommendation for banana grown on a clayey, mixed isohyperthermic Aquic Haplohumults under rainfed conditions. Five nitrogen rates (0, 85,170, 255 and 340 kg/ha/crop) were arranged in a randomized compíete block design with three replications. The nitrogen treatments were applied with 24.4 kg/ha of phosphorus, 651,7 kg/ha of potassium, and a minor element mixture containing 22.7 kg/t of fertilizer. Treatments were applied every three months. Applications of magnesium alone were also applied between treatments at the rate of 55 kg/ha in the plant crop (PC) and 110 kg/ha in each of two ratoon crops (R1, R2). During growth and development of three crops we collected data of plant and bunch traits, green and oven-dry biomass weight, nitrogen concentration in various plant organs, and bunch marketable weight at harvest. Results showed that the rate x crop interaction was highly significant (P < 0,01) for total nitrogen uptake, and for nitrogen concentration in the leaf-lamina four months before bunch harvest, and significant (P < 0.05) for total dry matter production. Total nitrogen uptake, leaf nitrogen concentration, and total dry matter production linearly increased with increments in the nitrogen rates. Overall total nitrogen uptake and total dry matter production were always significantly higher in the R2 than in the PC, Regardless of the nitrogen rate, a significantly higher nutrient concentration was always found in the leaf-lamina of the R1 plants than in either the PC or the R2 plants. Crop had no significant effect on yield, but nitrogen rate significantly influenced yield. A maximum yield of 57,060 kg/ ha/crop was obtained with an estimated nitrogen application of 240 kg/ha. This amount corresponded to a leaf nitrogen concentration of between 2.75 and 2.85 g/kg. Since the maximum yield for all crops was obtained with a nitrogen application of only 240 kg/ha, we concluded that the linear response to fertilization in excess of this amount for total nitrogen uptake, nutrient concentration, and total dry matter production may be attributed to luxury consumption of nitrogen.