Persistence of repeated triadimefon application and its impact on soil microbial functional diversity

Abstract The effects of repeated applications of the fungicide triadimefon in agricultural soil on the microbial functional diversity of the soil and on the persistence of the fungicide in the soil were investigated under laboratory conditions. The degradation half-lives of triadimefon at the recommended dosage, simulated by a first-order kinetic model, were 23.90, 22.95, and 21.52 days for the first, second, and third applications, respectively. Throughout this study, no significant inhibition of the Shannon-Wiener index (H′) was observed. However, the Simpson index (1/D) and the McIntosh index (U) were obviously reduced (p ≤ 0.05) during the initial 3 days after the first triadimefon application and thereafter, gradually recovered to or exceeded the level of the control soil. A similar trend in variation but with a faster recovery in the 1/D and U was observed after the second and third triadimefon applications, respectively. Taken together, the above results indicate that the repeated application of triadimefon enhanced the degradation rate of the fungicide and the recovery rate of the soil microbial functional diversity. It is concluded that repeated triadimefon applications in soil have a transient or temporary inhibitory effect on soil microbial communities. Keywords: BIOLOGfungicidetriadimefonmicrobial diversitysoil Acknowledgments This work was supported by the National Nature Science Foundation of China (Nos. 20907040, 20877068), the National High Technology R&D Program of China (No. 2009AA06Z316), the Major State Basic Research Development Program of China (No. 2009CB119000), the Scientific Research Fund of the Zhejiang Provincial Education Department of China (No. Y200908848), and the Fundamental Research Funds for the Central Universities. Notes *RSD: relative standard deviation. *DT50 values followed by different letters within a column are significantly different (p ≤ 0.05).