Sources and application methods of boron in Eucalyptus crop

Abstract

Cerrado soils have low boron (B) content, making supplementation of this element through fertilization via soil and/or leaf is a common practice. It is therefore important to establish the best mode of application and source of B for the proper development of eucalyptus. Thus, the objective of this study was to compare the effect of B sources with high and low solubility on eucalyptus cultivation and to examine the effect of foliar application of the micronutrient. The experiment was conducted in an area located at 20o 34’ S latitude and 51o 50’ W longitude with an altitude of 305 m during the period from January 2012 to February 2014. The experiment was set up using a randomised complete block design with six treatments and five replications, in a 3 x 2 factorial scheme, consisting of 0 kg ha-1 of B, 1 kg ha-1 of B using boric acid as a source (high solubility, 17% B) or 1 kg ha-1 of B using borogran as a source (low solubility, 10% B), applied to the planting furrow, with or without foliar application of 0.5% boric acid in a solution with a volume of 250 L ha-1. Except for the case of foliar B application, there was an increase in plant height in treatments that received the micronutrient at planting, which differed significantly from the control. However, both sources, independent of solubility, exhibited similar results. The two foliar B applications were sufficient to cause an increase in plant height when compared to treatments without B application at planting, at 21 months. At 24 months after planting, an increase in leaf B was observed in treatments with foliar application. However, this did not improve growth, diameter at breast height (DBH) or timber volume of the eucalyptus clone. Both the application of B at planting (independent of the source used) and the foliar application of the element were sufficient to reduce the symptoms of B deficiency. With respect to the sources used at planting, at a dose of 1 kg ha-1 of B, both sources produced similar results for plant height, DBH and timber volume.