Nível crítico de fósforo por diferentes extratores químicos em Neossolo Flúvico alcalino cultivado com milho

Abstract

Due to lack of research concerning the availability of P in soils of the semiarid Northeastern Brazil, the objective ofthis research was to study the efficiency of four extractors in predicting phosphorus availability in cultivated corn inan alkaline Fluvent from Pernambuco and estimate the critical levels of P in the soil and in the aerial parts of plants.The experiment was carried out in polyethylene vessels filled with 4 kg of soil. The experimental design was in randomized blocks with four repetitions and six P doses (0, 37, 74, 148, 222 e 370 mg dm-3). Thirty days after the P application, soils were collected to determine P recovered by Mehlich-1, Mehlich-3, Bray-1 and Olsen extractors, and after that corn was sown. The used extractors differed statistically in the average levels of extracted P. The Plevels and amounts and accumulated in plants increased linearly with P doses applied to the soil, while the dry matter amounts increased in a curved line. The extracted P correlated significantly and positively with P accumulated in corn plants, although the low values of correlations coefficients. The P critical levels in soil changed within extractors, being Mehlich-1 the extractor with the highest critical level, for its greater ability to extract P from the soil.