Phosphate and potash fertilization on Acacia mearnsii De Wild. (Black wattle) plantation.

Abstract

Acacia mearnsii is the third forest species more planted in Brazil, especially in small farms at Rio Grande do Sul State. The species is also known as black wattle and is important as a source of tannin, timber, pulpwood and rayon. Its fast growth results in high demand of nutrients and fertilization is necessary to keep site productivity. In this paper it is reported the results of the application of four doses of Phosphorous (0, 20, 40, 80g/tree as P₂O₅) and three of Potassium (0, 20, 40g/tree as K₂O), in a factorial designed trial established on a chemically poor soil at the region of Ponta Grossa, State of Paraná, Brazil. Trees were implanted in a 3m X 2m spacing with 35 plants per plot. The fertilizers were applied in furrows between the rows at the moment of planting. The results obtained at 61 months allowed the following conclusions: Application of Phosphorous, Potassium and combination of both increased wood volume in relation to the control (from 19% to 70%). The greatest increase in wood volume (70%) were obtained for the combination of P and K with 40 g of P₂O₅ + 40 g of K₂O.