Disponibilidade de fósforo avaliada por diferentes extratores em solos alcalinos de Pernambuco

Abstract

P is one of the most limiting nutrients for plant development. It is widely used in agriculture due to its high degree of interaction with the soil. In poorly weathered and alkaline soils, such as those that occur in the Brazilian semiarid region, P is susceptible to precipitation with Ca, making it unavailable to plants. In Brazil, Mehlich-1 and anion exchange resin (AER) are the extractors most used for P analysis, however, there are differences regarding the efficiency of Mehlich-1 in less weathered tropical soils. Thus, it is essential to evaluate the efficiency of P extraction by several extraction methods in alkaline soils for the correct evaluation of fertility and fertilizer recommendation. The aim of this work was to evaluate the efficiency of Mehlich-1 and RTA in comparison to Mehlich-3 and Olsen in predicting the P availability for plants in alkaline soils. A test was carried out in a greenhouse with samples from six soils (Neossolo Flúvico, Nessolo Quartzarênico, Argissolo Vermelho-Amarelo, Latossolo Vermelho-Amarelo e Vertissolo) collected in the 0-20 cm layer and placed in pots with six increasing P doses, in four replications, in a randomized block design. After 30 days of P doses application and soil incubation, soil samples were collected to perform analysis of recovered P by the extractors. The pots were seeded with Brachiaria decumbens cv. Basilisk and at 30 days after emergence, the plants were collected to determine P in plant biomass. Plants remained in the pots for more 30 days, when the second cut was made. Plant growth parameters were obtained, dry biomass weight, P content estimated by different extractors and P absorbed and accumulated by the plant. These variables were evaluated as a function of P applied doses, being subject to analysis of variance and regression models were tested. Even with high levels of available P verified in the characterization of soils, there was a significant increase in the production of dry mass with increasing doses of P. Mehlich-1 overestimated the levels of available P, except for Vertisol. Mehlich-3 and Olsen are the extractors more correlated to accumulated P in plants. It is recommended the use of Mehlich-3 in semiarid soils with alkaline pH.