1. Laboratory Experiment

    The laboratory assessment of the impact of pesticides isoproturon, chlorpyrifos and tebuconazole on soil microbes has been completed. So far the dissipation and metabolism of the selected pesticides has been determined. For this a multiresidue analytical method was developed and validated for the measurement of the residues of the three parent compounds and the main metabolites including TCP for chlorpyrifos, monodesmethyl-isoproturon (MDIPU) and didesmethylisoproturon (DDIPU) for isoproturon. No metabolites of tebuconazole were determined during the study. The three pesticides were applied at three dose levels including x1, x2 and x10 the recommended dose, while an untreated control was also co-incubated for microbial measurements. A brief outline of the dissipation data are given below:

    Tebuconazole showed a dose-dependent trend with DT50s increasing from 63 to 79 and 99 days in the x1, x2 and x10 dose rates respectively.  Chlorpyrifos dissipated via formation of TCP, its main hydrolysis product which was further degraded until the end of the study. In contrast to the other two chemicals, chlorpyrifos showed a reduced persistence with increasing dose rates with DT50s ranging from 28.4 to 77 days in the x10 and x1 dose rate respectively. The dissipation of isoproturon proceeded via sequential demethylation to MDIPU, which was the main soil metabolite, while low concentrations of DDIPU were detected (not shown). Trace amounts of 4-isopropyl aniline were also detected sporadically in soil during the study. In accordance with tebuconazole, the persistence of isoproturon showed an increasing trend with increasing dose rates.

    Overall, the persistence of the three pesticides increased in the following order isoproturon >> chlorpyrifos >> tebuconazole. On-going radiorespirometry studies employed in INRA by Veronica Storck showed limited mineralization of the isoproturon and tebuconazole in soil while chlorpyrifos mineralization is pending. At the moment soil samples are processed for DNA extraction and the impact of pesticides on the activities of important soil exoenzymes is determined via high-throughput fluorometric assays.

    The laboratory experiment was employed by AEIFORIA srl, Italy and the seconded fellows involved were E. Papadopoulou, P. Karas and S. Nikolaki

  2. Field Experiment

    A field experiment with the same chemicals and dose rates of x0, x1, x2 and x5 (maximum allowed for experimental purposes) were utilized. The experiment was initiated at 5 November 2013 on a field cultivated with winter wheat in the Piacenza province, Italy. Currently, the field experiment is at the 56th day after pesticide application and it is expected to be terminated in March when the final samples will be collected. A photograph of the field site and the orientation of the experimental plots are shown below. 

    Four microplots per treatment were established following a completely randomized design. Samples have been collected from the field 0, 4, 7, 14, 21, 42 and 56 days and samples are processed for dissipation measurements or stored for microbial measurements.

     Photograph of the calibration of the sprayer before pesticide application (Piacenza November 2013)

       P. Karas and S. Nikolaki are the two seconded fellows which are currently involved in the field experiment




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