| Abstract: | An experiment has been carried out in cultivated drainage lysimeters filled with reported soil in order to investigate on the disappearance and mobility of Metolachlor and Terbuthylazine as related to the nitrogen fertilization level. Two experimental units have been compared: in the O-N treatment the soil did not receive N fertilizers during the 7 years previous to the experiment, whereas in the H—N treatment the average application rate of nitrogen during the same period was 220 kg ha?1 year?1; a corn crop has been cultivated in the present experiment. The active ingredients have been analysed in the artificial soil profile (from 0 to 40 cm, by 10 cm soil layers) and in leachates. The disappearance rate of Terbuthylazine was affected by nitrogen fertilization level, as the half life resulted about 7 days higher in O—N (21.9 days) treatment than in H—N (14.6 days). On the contrary, N fertilization did not significantly modify the half life of Metolachlor (17.2 and 15.9 days at O—N and H—N, respectively). A N-dealkylated degradation product of Terbuthylazine has been found in the shallow soil layers. The distribution pattern of herbicides content in the soil profile showed that Terbuthylazine was less mobile than Metolachlor. Leachates did not contain Terbuthylazine at all, but amounts of Metolachlor close to the detection limits (25 μg L?1). |
