Phytotoxic Effect of Brachiaria decumbens Extract on the Development of Eucalyptus urograndis Seedlings

The objective of this work was to evaluate the phytotoxic effect of Brachiaria decumbens Stapf. on the morphometry of Eucalyptus urograndis plants, genetically modified hybrid of Eucalyptus urophylla S. T. Blake × Eucalyptus grandis W. Hill ex Maiden. Pots containing the eucalyptus plants were conditioned in protected environments in a completely randomized experimental design. The treatments were composed of aqueous extract of Brachiaria decumbens grass at different concentrations: 0% (control, distilled water only), 20%, 40%, 60%, 80% and 100% (g/L). On day 30 of the experiment, the following morphological parameters of the plants were evaluated: aerial part height, diameter of stem, aerial dry mass, root dry mass, total dry mass, and robustness index. The data were submitted to analysis of variance at the 5% level of significance, and a regression equation was constructed for the quantitative treatments. The results indicated that the Brachiaria decumbens grass extract did not have an inhibitory effect on aerial part height and robustness index. However, the extract at concentrations higher than 20% had negative effects on root dry mass, aerial dry mass, and total dry mass. For the diameter of the stem, only concentrations above 60% had an inhibitory effect.