Adsorção e lixiviação de boro em Latossolo Vermelho-Amarelo

Abstract

Resumo -O objetivo deste trabalho foi avaliar a adsorção e a lixiviação do boro em Latossolo Vermelho-Amarelo distrófico, cultivado com soja, em conseqüência das doses de boro e da calagem. Foram analisadas amostras de um solo do Estado do Mato Grosso, cultivado com soja durante três anos, com doses de 0, 1,5, 3, 4,5, 6, 7,5 e 9 Mg ha -1 de calcário, e 0, 1, 3, 5, 7 e 10 kg ha -1 de boro, aplicados no primeiro ano de cultivo. Foram determinadas isotermas de adsorção de boro em função da calagem e do tempo de cultivo, assim como a lixiviação em função da calagem e da adubação boratada. No caso da calagem, mesmo com doses relativamente altas de calcário, a adsorção de boro pelo solo é muito alta apenas no ano de aplicação do corretivo, e diminui significativamente com o tempo. No entanto, a lixiviação de boro guarda estreita relação com o teor do nutriente no solo e com a dose do nutriente que é aplicada, mas é pouco influenciada pela calagem.Termos para indexação: ácido bórico, adubação, calagem, micronutrientes. Boron adsorption and leaching in a Brazilian OxisolAbstract -The objective of this work was to evaluate soil boron dynamics in a Typic Hapludox cropped with soybean for three years, as affected by boron rates and liming. Soil samples were taken during three years from a field experiment with lime rates of 0, 1.5, 3, 4.5, 6, 7.5 and 9 Mg ha -1 and boron rates of 0, 1, 3, 5, 7 and 10 kg ha -1. Boron adsorption isotherms as affected by liming and time under cropping were determined. Boron leaching, as affected by boron fertilization and liming was also evaluated. When lime was applied, even at high rates, soil boron adsorption was very high only in the first year, and decreased with time. Boron leaching, though not affected by liming, is strongly related to soil boron contents and boron fertilization.

Boron adsorption in lowland soils from Paraná State, Brazil

“…For soils from São Paulo State, Alleoni and Camargo (2000), using the same B concentrations, found adsorbed B values from 0.6 to 11.1 mg kg -1 soil regardless of liming. Analyzing samples of clayey Latosol from a field experiment with liming, Rosolem and Bíscaro (2007) found maximum adsorbed B values between 9.5 mg kg The values of Langmuir constants (Table 3) were similar to those found in studies using a range similar to the B concentration added to the soil. The bonding energy of B to the soil (K L ) ranged from 0.16 to 2.22 L mg -1 , while the maximum adsorption capacity (Ads max ) ranged from 3.0 to 35.7 mg B kg -1 soil.…”

“…However, Rosolem and Bíscaro (2007) found that even by applying relatively high doses of lime, the B adsorption by soil is only significant in the year that the liming was carried out, so that over time a greater amount of B remains in the soil solution under conditions of being readily absorbed by plants or even being lost by leaching. Similarly, Chen, Ho and Lee (2009) observed that soil re-acidification caused an increase in B desorption, increasing the element's content in solution.…”

“…Thus, it is expected that the acidity correction in soil until pH 6.0, as recommended for most crops, increases the B adsorption in the soil. 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.…”

<b>Effect of liming on micronutrient availability to soybean grown in soil under different lengths of time under no tillage

“…Liming generally decreases the B content because Al 3+ in solution is precipitated in the form of Al(OH) 3 , which has the ability to adsorb large amounts of B (Tisdale et al, 1985;Prodromu, 2004;Rosolem & Bíscaro, 2007). The low exchangeable Al in these soils (Table 1) may explain the lack of response of B to liming.…”

“…The extractable soil B in the surface layer seems to have been related more to the amount of OM, which is an important source of this element (Tisdale et al, 1985;Rosolem & Bíscaro, 2007;Rosolem, Zancanaro, & Bíscaro, 2008), than to the soil pH. In the first sampling (V4 stage), the correlation coefficient between extractable soil B and OM was positive for all layers (correlation coefficient in the surface layer was 0.56), thus agreeing with results obtained by Alleoni, Camargo, and Valadares (1999) for soils in the State of São Paulo.…”