Eficiência da adubação boratada no desenvolvimento de mudas de eucalipto

Given the economic importance of eucalyptus (Eucalyptus urograndis) to Brazil and the influence of boron on this crop, he objective of this study was to evaluate the effect of doses and forms of boric acid application on the initial development of newly transplanted eucalyptus seedlings. The experiment was carried out in greenhouse, in plastic containers with a capacity of 10 L of soil. The experimental design was completely randomized (DIC) in a 2 × 5 factorial scheme with four replications, the two forms of application (via boric acid leaf containing extract of the seaweed Ascophyllum nodosum and via soil with boric acid) and five doses of boron (0, 0.39, 0.77, 1.54 and 3.08 mg L-1). At 45 days after transplanting, biometric evaluations and root, stem and leaf sampling were performed to determine B. It was observed that the boron content in the leaves and stem of the eucalyptus increased linearly until the highest dose of B, without symptom of phytotoxicity. The application of B via soil at the dose of 1.54 mg L-1 is more efficient than the foliar application because it provides a higher leaf content of the nutrient. However, foliar fertilization of B + algae extract provided foliar B contents within nutrient sufficiency ranges for eucalyptus, and did not differ from fertilization via soil at other doses. The doses and forms of application of B do not differ in relation to the height, collection diameter and dry mass of the eucalyptus seedlings.