Disponibilidade de fósforo e produção de biomassa de pinhão manso em solos com distintas texturas e doses de fósforo

Abstract

Knowledge of the nutritional needs of Jatropha curcas L. is of the utmost importance when grown in Brazilian soils, where the use of fertiliser is necessary for the success of the crop. The aim of this research was to evaluate phosphorus (P) availability by the Mehlich 1, Olsen and Anionic Exchange Resin extractors, as well as biomass production in the Jatropha grown in a Latosol with different textures and doses of P. The experimental design was of randomised blocks in a 2 x 6 x 3 factorial scheme, with three replications. The treatments resulted from the combination of two soils (clayey and sandy), six doses of P2O5 (50, 100, 150, 200, 250 and 300 kg ha-1) and three extractors (Melich 1, Olsen and Anion Exchange Resin). The Jatropha was grown in pots for 90 days, when soil samples were collected to determine the P content by means of the extractors. The biomass production and P content of the plant were higher in the sandy soil. Leaf production and the P content of the leaves, stalk and roots increased linearly up to the dose of 300 kg ha-1 P2O5, indicating a high demand for P in this crop. The Mehlich 1 extractor quantified higher levels of P compared to the Olsen and Anion Exchange Resin, possibly due to its ability to extract P-Ca from the soils due to their limestone origin. However, the P content extracted with the Anion Exchange Resin and Olsen extractors displayed a greater relation to the P content and biomass production of the Jatropha, being more suitable for evaluating the P available for the initial development stage of the crop.a.