Fracionamento inorgânico do fósforo em dois tipos de solo tratados com Biochar no cerrado

Abstract

Cerrado soils are highly weathered, acidic, with low natural fertility and high concentrations of aluminum. In spite of being well structured soils with physical properties favorable to agricultural production, such as high stability of aggregates, the mineral complex of these soils is predominantly composed of kaolinite and iron and aluminum oxides and hydroxides, which provides low exchange capacity Cationic and high adsorption of phosphorus (P). Thus, studies aiming to propose new management techniques that aim to increase the availability of P in the soil in fractions of greater solubility are important. In this context, biochar may be an agronomically viable alternative to increase P-labile in the soil. Therefore, knowing the nature and the distribution of the fractions of P is important to understend the availability of these elements to the plants. In this context, it was verified the effect of the biochar in the fractions of P in the soil. For this, two field experiments were conducted in two different soils, Red-Yellow Latosol (Oxisol) (Experiment I) and the second in a Plintossolo Háplico (Entisols) (Experiment II). The experiments were designed in a randomized block design with a combination of two levels of base fertilization (0 and 300 kg ha-1 of the formula 00-20-20 NPK fertilizer) and doses of biochar (0, 2, 4, 8 and 16 Mg ha-1 for the experiment I and 0; 8; 16 e 32 Mg ha-1 for the experiment II) in four replicates. The fractions of P-soluble, P-Al, PFe, P- unavailable and P-Ca were evaluated by sequential chemical fractionation at depths of 0 to 10 cm and 10 to 20 cm. The application of biochar in experiment I reduced the levels of P-Al, P-Fe and P-unavailable, and increased the levels of P-soluble. No effect was observed for P-Ca. In the experiment II, it was observed in doses above 16 Mg ha-¹ of biochar, reduction in the levels of P-Al, P-Fe, P-Ca and P-unavailable, and increase in Psoluble contents. Regardless of the fractions of P, the highest levels were observed in the 0 to 10 cm layer in the two types of soils studied. Biochar proved to be efficient in reducing P forms of low solubility making it more labile and consequently more available to plants. The application of biochar together with phosphate fertilizers can increase efficiency in fertilizer and nutrient use.