Silicon-phosphorus interactions in soils cultivated with eucalyptus under greenhouse conditions

This experiment had the objective of evaluating the P-Si interactions in two soils by nutritional parameters of P in Eucalyptus grandis cuttings under effect of Si application. Two experiments were conducted in greenhouse conditions utilizing the surface layers (0-20 cm in depth) of Dark-Red Latosol cerrado phase and of Cambisol campo cerrado phase of the physiographic zone Campos das Vertentes, MG, Brazil. Each soil was submitted to three sequential incubations: CaCO3 + MgCO3 p.a. to keep pH around 6.0; basic fertilization, including P in a single dose calculated to maintain 0.2 mg L-1 of P in solution; and six doses of Si (CaSiO3) defined on the basis of the dose of P. The production of dry matter of the aerial part (DMAP), contents of P and Si in the DMAP and phosphate fractions and acid phosphatase activity in plants were evaluated at 60, 90 and 120 days after the transplanting of cuttings to the pots. Multiple regression equations of these variables were adjusted in terms of doses of Si and of the evaluation times. Cuttings cultivated in the Cambisol presented gain of 15.25% in contents of P in the DMAP. Phosphorus fractions and acid phosphatase activity were not sensible to evaluate Si-P interaction at soils studied.