Boron adsorption by soil: effects of boron concentration and soil pH

Abstract

To study the influence of the soil pH and the boron content on its adsorption by soil, an experiment was carried out in laboratory conditions utilizing a Dark-Red Latossol, medial texture collected in Jaboticabal, SP, Brazil, at the first 20 cm layer. Five different boron levels in the soil were obtained by adding 4 ml of boric acid solution containing respectively 15, 30, 45, 60 and 75 µg/ml of boron to 10 ml soil samples with the following pH (in 0.01 M CaCl­₂) values: 4.2, 4.6, 5.0, 5.2 and 5.6. The results obtained showed an increasing of boron adsorption by soil with the increase of the boron added. Except between the dose of 45 and 60 µg/ml of boron, in all other cases, the contents of the adsorbed boron were statistically different. Also, it could be seen and increasing boron adsorption with the increase of the soil pH at all boron levels, except at the higher dose. In this case, the absence of significant difference was attributed to the lower effeciency of the extraction method at high boron levels.