Efeitos de diferentes dosagens de adubação no crescimento inicial de Eucalyptus benthamii na região sul do estado do Paraná

Abstract

The effects of different dosages of fertilizers in the initial growth of Eucalyptus benthamii were studied in the municipality of General Carneiro, Parana southern region. A completely randomized design under different fertilizer dosages with sample units of 250 m² (six treatments and eight repetitions) and initial spacing of 2.5 m x 2.5 m to six years old was used. We evaluated the initial mean growth in diameter, total height, cross-sectional area and volume (total and by assortment), as well as the production mean per hectare of the basal area, total e commercial volume, besides the survival capacity. The study evaluated the growth and production of E. benthamii in a region with severe winters under different dosages of fertilization with or without addition of base fertilization with NPK applied in different periods of time. Hypsometric models were adjusted per treatment and taper functions were also fitting using 27 trees cubed. The data were submitted to the Bartlett test for all studied variables, analysis of variance (ANOVA) and the Tukey test to verify the differences between treatment means. The adjustments showed that the Trorey hypsometric model is the best model to estimate total height and the Hradetzky polynomial of fractioned potencies the most appropriate function to estimate diameters at different heights and the total volume. It can be proved, through the obtained results, that the application of base fertilization (28.8 Kg ha-1 from P2O5, 30.4 Kg ha-1 from Ca and 17.6 Kg ha-1 from S), and covering fertilization at day 30 (14.4 kg ha-1 from N, 72 Kg ha-1 from P2O5, 14.4 Kg ha-1 from K2O, 0.12 Kg ha-1 from B and 0.48 Kg ha-1 from Zn), and at days 60 and 90 (2 applications of 36 kg ha-1 from N, 12 Kg ha-1 from P2O5, 72 Kg ha-1 from K2O, 0.48 Kg ha-1 from B and 0.05 Kg ha-1 from Zn) provides greater individual medium growth rate, total volume, commercial volume and volumetric MAI. The species is resistant to the frequent frosts in southern Brazil, with MAI values of 54.4 m³ ha-1 yr-1, where the gross income of the treatment that received fertilization when compared to the control treatment is superior than R$ 4,769.00 per hectare.