Abstract: By potting experimental method, we studied effect of nanoTiO₂ on the activity of Azotobacter in sandy soil, black soil and peaty soil. The results show that nanoTiO₂ inhibit the activity of Azotobacter in different types of soil, and the order of inhibition is sandy soil>black soil>peaty soil. The inhibitory rate of Azotobacter increases with the increase of the dosage of nanoTiO₂ at different doses （0.5,1.0,2.0 g/kg） in sandy soil and peaty soil. 2.0 g/kg nano TiO₂ are added to sandy soil and peaty soil, and the inhibition ratio reaches the maximum at the 15th day, 25.73% and 12.76% respectively. After planting of alfalfa in three soils, the rhizosphere effect and root exudates can indirectly reduce the inhibitory effect of nanoTiO₂ on Azotobacter. The difference is extremely significant between the planted group and the unplanted group (P<0.01) in the black soil and peaty soil, and the difference is significant between the planted group and the unplanted group (P<0.05) in the sandy soil.

Key words: inhibition, soil, nanoTiO₂, Azotobacter