| Semen Coicis is one of the important Chinese traditional medical herbs. carbendazm is usually used for the control of Jobstears smut in the production of Semen Coicis. To evaluate the safety of carbendazim application on Semen Coicis, studies were conducted on dissipation and residue dynamics of carbendazim on Semen Coicis and in soil, and its influences on soil microbial diversity. The results were summarized as follows:In Taishun and Jinyun, the degradation of carbendazim on Semen Coicis and in soil followed the first-order function. The half-life of carbendazim was measured to be 8.2d and 13.2d in Semen Coicis, 13.3d and 3.3d in soil after its application at dose of 1500g.ai.ha-1, respectively. Similarly, the half-life of carbendazim was 8.3d and 11.8d in Semen Coicis, 14.1d and 4.2d in soil after its application at double dose, respectively.The residues were found to be 0.08-0.27 mg kg-1 in Semen Coicis, ND-1.14 mg kg-1 in soil 21 and 30 days after application of carbendazim at the recommended dosage (1500g.ai.ha-1) and the high dosage (3000g.ai.ha-1), respectively.The half-life of carbendazim in soil under laboratory conditions was measured to be 8.6 and 6.8d at levels of 2.0 mg kg-1 and 4.0 mg kg-1, respectively. Significant reduction in the richness, evenness and superiority of soil microorganisms was observed within initial periods after carbendazim treatments. The inhibitory effect of carbendazim on soil microorganisms was increased with concentration of carbendazim in soil. After initial variations, soil microorganisms adapted gradually to carbendazim and recovered to similar levels of the controls without carbendazim.The degradation rate of carbendazim at the level of 10 mg kg-1 increased gradually after its repeated application to soil. The effect of carbendazim on soil microbial community was not significant after the first treatment. Soil microorganisms were stimulated by the second and the third addition of carbendazim. Meanwhile, the evenness was enhanced. No significant effect on soil microorganisms was observed after the fourth treatment of carbendazim. |
