AVALIAÇÃO DA DISPONIBILIDADE DO FÓSFORO NO SOLO POR MÉTODOS ISOTÓPICO, QUÍMICOS E BIOLÓGICO

An experiment was carried out in greenhouse with the objective of evaluating soil P by chemical (extraction by Bray 1, Mehlich 1, Mehlich 3 and resin), isotopic (E value) and biological (dry matter production of rice plants) methods. A Red Yellow Latossol (dystrophic) was used. The experimental design was a completely randomized 4x3: 4 rates of P (0, 50, 100 and 200 mg kg-1), 3 thermophosphate sources (Yoorin MC, Yoorin MG and Yoorin semi finished) and triple superphosphate (100 mg kg-1) with three replicates. Main conclusions were: the best correlations were found between either dry matter or P taken up with Mehlich 1 and resin extraction; these two extractant solutions showed also the closest correlation (r = 0,96). The rate 200 mg kg-1 of Yoorin MC and Yoorin semi finished produced the highest dry matter yield. The highest index of agronomic efficiency, however, was achieved with Yoorin semi finished.

thermophosphate; resin; rice; Oryza sativa; Phosphorus; distrophic red-yellow latostd; soil; extractors


São Paulo - Escola Superior de Agricultura "Luiz de Queiroz" USP/ESALQ - Scientia Agricola, Av. Pádua Dias, 11, 13418-900 Piracicaba SP Brazil, Tel.: +55 19 3429-4401 / 3429-4486, Fax: +55 19 3429-4401 - Piracicaba - SP - Brazil
E-mail: scientia@usp.br