NITROGEN EFFECT ON NUTRITIONAL STATE AND ON BIOMASS PRODUCTIVITY IN EUCALYPTUS DUNNII MAIDEN MINISTUMPS

Abstract

The aim of this study was to evaluate the nutritional state and the biomass production of ministumps of Eucalyptus dunnii Maiden submitted to fertirrigation with nitrogen different forms and doses. The clonal minigarden of 90 days seedlings was cultivated in the commercial substrate of pine sp bark and vermiculite (tubes of 55 cm³). Different forms of nitrogen were tested in the concentration of 0.4 g L^-1 (NO₃^-, NH₄⁺ and NO₃^- + NH₄⁺), the nitrogen sources were: KNO₃, (NH₄)₂SO₄ and NH₄NO₃, respectively. In the dose test an unique source (NH₄NO₃) was used in the following concentrations of N: 0.2; 0.4 and 0.6 g L^-1. Each ministump was weekly watered with 10 mL of the tested solution. At 42 days of experiment, foliar samples were collected for determining  the nutritional state. At 157, 185 and 216 days, minicuttings was collected for determination of the biomass production. None of tested nitrogen forms and doses showed negative effect on foliar nutritional state of the minicuttings. The dry biomass production was bigger for the NO₃^- +NH₄⁺ form and for 0,6 g L^-1 dose. In conclusion, the NO₃^- +NH₄⁺ N form and the 0,6 g L^-1 N were recommended. Bigger N doses can be able to increase the biomass production in the clonal minigarden of E. dunnii.