Substituição parcial de fosfato solúvel por natural na implantação de Eucalyptus benthamii e Eucalyptus dunnii no planalto sul catarinense

Abstract

Phosphorus fertilization is important for the initial growth of eucalyptus. Soluble phosphate (SP) sources are commonly used for this purpose because they offer fast dissolution in the soil, but these sources have higher costs than rock phosphate (RP), which has lower solubility. The aim of this study was to evaluate the use of RP as a partial substitute for SP for the initial supply of P to Eucalyptus benthamii and E. dunnii. Two field experiments were carried out (one with each species) in the municipality of Otacílio Costa, SC, Brazil, from November 2010 to December 2011. A randomized block experimental design in a split plot arrangement with three replications was used. In the main plot, the presence or absence of RP (0 or 60 kg ha-1 of P2O5 using Bayovar as a P source) was tested, and in the subplots, application rates of SP (0, 75, 150 and 300 kg ha-1 P2O5, using triple superphosphate) were tested. The diameter was measured at the root collar as well as tree height at 340 days after applying the P sources. The results showed that P fertilization promoted plant growth in diameter and height, increasing the volume of E. benthamii and E. dunnii during the first year of cultivation. E. benthamii was more demanding in P, but allowed partial replacement of soluble phosphate by a source with lower solubility. There was no response from E. dunnii to the application of rock phosphate, and fertilization should be performed only with soluble phosphates.