Fracionamento químico do fósforo e da matéria orgânica em um latossolo de cerrado sob aplicação de Biochar

Abstract

Cerrado has highly weathered, acidic, poorly fertile soils with high concentrations of aluminum. Regardless of these characteristics, these soils possess favorable qualities for agricultural production, despite having mineralogy that causes low CTC and high adsorption of phosphorus. On the other hand, soil organic matter (SOM) under constant modification, high temperatures, humidity and management aspects accelerated this process. In view of this reality it is important to seek new management techniques that provide greater availability of phosphorus in more soluble fractions and the permanence of organic carbon in the soil. Therefore, the objective of this work was to verify the effects of biochar on the phosphorus (P) and MOS fractions in a Yellow Red Latosol. A randomized block experiment with two levels of base fertilization (0 and 200 kg ha-1 of NPK formula 00-20-20) and five doses of biochar (0, 2, 4, 8 and 16 Mg ha-¹) in four replicates. The fractions of P-soluble, P-Al, P-Fe, P-occlusal and P-Ca were evaluated by sequential chemical fractionation at depths of 0 to 10 and 10 to 20 cm and also the carbon contents in the fulvic acid, humic acid and humin fractions, by chemical fractionation of MOS at depths of 0 to 10 and 10 to 20 cm. For phosphorus, a reduction in PAl, P-Fe and P-occlusion levels was observed, increasing P-soluble contents, making it more available to plants. No effect was observed for P-Ca. The highest levels were observed in the 0-10 cm layer. For organic matter at doses above 8 Mg ha-¹ of biochar, it observed the reduction in the carbon contents of the fulvic and humic acid fractions, most evidently in the presence of NPK. Regardless of the dose, biochar increased the carbon content in the humina fraction. In general, in the 0 to 10 cm layer the highest C contents were obtained in the NPK treatments, already in the depth of 10 to 20 cm the highest contents were obtained in the absence of fertilization.