Emprego dos extratores mehlich e resina trocadora de ânions para avaliação do fósforo disponível para soja em latossolo vermelho-escuro distrófico em Goiás

Abstract

The Mehlich extractor has been used ai the School of Agronomy of the U.F.G .. in the State of Goiás since 1966. Therefore, some laboratories which operale in the "Cerrado regions are beginning to use the Anion Exchange Resin Method. This experiment compared the two extractors, using three different sources of phosphorus; natural powdered phosphale (FN), hyperphosphate (H), and tripie superphosphate (S1) in doses of O, 200, 400 and 600 K of P20, per hectar. The two extractors showed a correlation for these sources oí phosphate. However the results differed because of the of wue responses. Between the zero dose of PP, per hectar, of natural phosphate, the Mehlich extractor extracted 685,2% more for a produclion increase of soybeans of only 20.6%. At the sarne time, the resin mcthod extracted only 81,26% more for the sarne phosphale variation. Changing the quantily of P p, from a lo 600 k per hectar o( tripel superphosphate., production increase in soybeans was 40,3 %, which corresponded to an increase of 316,6% in extraction using the amin exchange resin method an 241,9% using the Mehlich Method. It was conclued that the resin melhod was more efficient because it manifes1ed a be1ter correlation in superphosphate, but hostly because il extracted less natural phosphate.