Sorption of the toxin of Bacillus thuringiensis subsp. kurstaki by soils: effects of iron and aluminium oxides

Transgenic Bacillus thuringiensis (Bt)‐modified plants release Bt toxins into soil and, as a result of worldwide adoption of this technology, concern about their environmental effects has arisen. The sorption of Bt toxin has been studied on four contrasting soils: latosol (Ferralsol), latosolic‐red soil (Ferralsol), red soil (Acrisol) and paddy soil (Anthrosol). Sorption of Bt toxin was also measured on residues of these soils after chemical treatment to remove free (Fed and Ald), amorphous (Feo and Alo) and exchangeable Fe and Al (FeEx and AlEx). The results indicated that the specific surface area (SSA) of soils decreased after the removal of Fe and Al, especially after the removal of Fed and Ald. However, the absence of these three species of Fe and Al did not have a significant effect on the organic matter (OM) content of soil residues when compared with their intact soils. The presence of Fed and Ald, Feo and Alo and FeEx and AlEx increased the sorption of Bt toxin by soil, and the influence of Fed and Ald (with about 46% decrease) was greater than the effect of the other two species of Fe and Al.