Abstract
Boron adsorption was studied in five representative soils (Rhodic Hapludox, Arenic Paleudalf and three Typic Hapludox) from the State of São Paulo, Brazil. Adsorption was higher in the clayey Oxisols, followed by the Alfisol and the coarser Oxisols. Calcium carbonate promoted an increase in the amount of adsorbed boron in all soils, with the most pronounced effect in the coarser-textured Oxisols. High correlation coefficients were found between adsorbed boron and clay and amorphous aluminum oxide contents and specific surface area (r = 0.79, 0.76 and 0.73, respectively, p < 0.01). Clay content, free aluminum oxide, and hot CaCl2 (0.01 mol L-1)-extracted boron explained 93% of the variation of adsorbed boron. Langmuir and Freundlich isotherms fitted well to the adsorbed data, and highest values for maximum boron adsorption were found in clayey soils, which were significantly correlated with contents of total, free and amorphous iron and aluminum oxides, as well with the physical attributes. Ninety four percent of the variation in the maximum adsorption could be related to the free iron content.
Highlights
There are many differences in the behavior of plant species and even some varieties within a species have different responses regarding micronutrient deficiency or toxicity
Total and amorphous Al contents, specific surface area and clay contents are significantly correlated with adsorbed B; in the multiple regression, clay, free aluminum oxide and soluble B contents are correlated with B adsorption by soils, explaining 93% of its variation
As the values of adsorbed B are mainly explained the concentration of soluble B (Bsol) in soils and by texture, B fertilization recommendation in São Paulo State, can be based on these soil factors, as it is already for cotton and coffee
Summary
There are many differences in the behavior of plant species and even some varieties within a species have different responses regarding micronutrient deficiency or toxicity. Fertilizer recommendations in São Paulo State consider only such cases where micronutrient deficiencies are observed, mainly with Zn and B (Raij et al, 1996). Residual effect due to fertilization can be extended for many years, depending on the applied amounts. L.R.F. ALLEONI and O.A. DE CAMARGO when monitoring soil analysis, one can prevent B accumulation, whose probability of toxicity is high. Depending on the available soil B content already present in soils, 0.5 to 2.0 kg ha-1 are applied to deficient soils in São Paulo
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