Adsorção de boro em solos de várzea do Sul de Minas Gerais

Abstract

O objetivo deste trabalho foi avaliar a adsorção de B em quatro solos de várzea da região de Lavras, MG, por meio dos parâmetros das isotermas de Langmuir e Freundlich, no período de outubro a novembro de 1998. Amostraram-se solos Aluvial, Glei Pouco Húmico, Glei Húmico, e Orgânico artificialmente drenado, coletados na camada de 0-20 cm e peneirados para 2 mm. Amostras com e sem calagem foram incubadas durante 30 dias. Duplicatas de 4,0 g de solo de cada classe foram acondicionadas em tubos de polietileno com oito diferentes doses de B (0, 2, 4, 8, 12, 16, 24 e 32 mig mL-1) preparadas em CaCl2.2H2O 0,01 mol L-1, com ácido bórico como fonte. Os teores de B na solução de equilíbrio foram determinados pelo método da Azometina-H. Os resultados mostraram que alto teor de matéria orgânica confere ao solo Glei Húmico maior capacidade de adsorver boro. A matéria orgânica, a superfície específica, caulinita e alumínio trocável foram os atributos dos solos que se correlacionaram diretamente com a capacidade máxima de adsorção de B (CMAB). A calagem proporcionou diminuição da CMAB em todos os solos.

Boron extraction and vertical mobility in Paraná State oxisol, Brazil

“…While B mobility is favored by acidic conditions, the movement of the element in deeper layers is related to the application time and rate, initial concentration of the element (Rosolem & Biscaro, 2007), quantity of percolated water (Patil et al, 1997;Communar & Keren, 2006 and magnitude of soil absorption. Azevedo et al (2001) affirm that B absorption directly correlates with organic material content, specific clay surface, presence of kaolinite, and exchangeable Al.…”

Boron adsorption in lowland soils from Paraná State, Brazil

“…Similarly, the percentage of B adsorption (%Ads) measured after addition of 2.0 mg L -1 increased with liming (Table 3). Contrasting results were reported by Azevedo, Faquin and Fernandes (2001), working on four lowland soils in southern Minas Gerais, Brazil, who found decreased B adsorption capacity in all soils when lime was applied.…”

“…2 (GOLDBERG;SHOUSE, 2008;CORWIN;SUAREZ, 2005 The existence of a correlation between the maximum adsorption and pH was previously reported by Evans (1987) in bit weathered Canadian soils. On the other hand, a lack of correlation between Ads max and soil pH was verified by Azevedo, Faquin and Fernandes (2001) in lowland soils of Minas Gerais, and by Alleoni and Camargo (2000) and Soares, Casagrande and Alleoni (2008) in acric soils of São Paulo State.…”

“…Most probably, with the increased B concentration, more sites were taken and the occurrence of the reaction was more difficult, decreasing the curve inclination ( Figure 1). Valladares, Pereira and Alves (1998) found B adsorption isotherms type H for the lowland soils of Rio de Janeiro State, while Azevedo, Faquin and Fernandes (2001) found adsorption isotherms of types L and H for the lowland soils of Minas Gerais State, the latter when the pH was low.…”

“…In clayey Latosol of Mato Grosso State, Brazil, Rosolem and Bíscaro (2007) found that the application of 9.0 Mg ha -1 lime incorporated in the 0-20 cm layer increased seven times the maximum amount of adsorbed B in the first year. However, in lowland soils of southern Minas Gerais State, Brazil, Azevedo, Faquin and Fernandes (2001) found that liming decreases the maximum adsorption capacity of B. These contradictory results indicate the need for more research to be conducted, particularly for lowland soils that vary widely in their physical, chemical and mineralogical characteristics, result of the origin material heterogeneity and the different levels of their hydromorphic state.…”