Abstract: This paper studied the characteristics of the adsorption and desorption of Bt (Bacillus thuringiensis)toxin on goethite, kaolinite, and silica. The results showed that in phosphate buffer (pH 8), the adsorption isotherms ofBt toxin on the test minerals followed Langmuir equation (R²>0.9661), and the adsorbed amounts were in the order of goethite﹥kaolinite﹥silica. The Btoxin was easily adsorbed on the minerals, and the adsorption could reach equilibrium after 1 hour. Within the range of pH 6-8, the amounts of Bt toxin adsorbed on goethite, kaolinite and silica decreased with increasing pH; in the range of 10 ℃-50 ℃, the amounts of the toxin adsorbed on goethite and silica decreased by 8.39% and 47.06%, respectively, while that on kaolinite increased slightly (5.91%). The infrared absorption spectrum showed that there was only a minor alteration of Bt toxin after adsorption. The toxin adsorbed on the minerals was not easily desorbed by deionised water, with the desorption rate ranged from 28.48% to 42.04% after three times washing.

Key words: wheat after rice, tillage and sowing practice, soil nutrient uptake and utilization, grain yield, tillering capacity