BEHAVIOR OF METOLACHLOR AND TERBUTHYLAZINE LYSIMETERS

An experiment has been carried out in cultivated drainage lysimeters f illed with reported soil in order to investigate on the disappearance and mobility of Metolachlor and Terbuthylazine as related to the nitro gen 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 av erage application rate of nitrogen during the same period was 220 kg h a(-1) year(-1); a corn crop has been cultivated in the present experim ent. The active ingredients have been cultivated in the present experi ment. 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 fertili zation 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 fertili zation did not significantly modify the half life of Metolachlor (17.2 and 15.9 days at O-N and H-N, respectively). A N-de-alkylated degrada tion product of Terbuthylazine has been found in the shallow soil laye rs. The distribution pattern of herbicides content in the soil profile showed that Terbuthylazine was less mobile than Metolachlor. Leachate s did not contain Terbuthylazine at all, but amounts of Metolachlor cl ose to the detection limits (25 mu g L(-1)).