The purpose of this study was to investigate the fate of triazines and their metabolites in the unsaturated zone in the field conditions during a period from the spring sowings to the autumn tillages. The study was performed upon two soils treated for corn culture during the year 1992. The investigations were presented after the wet weather by subsurface drainage and surface runoff. Throughout the 6 months survey, the relative importance of the triazines is by decreasing order: atrazine > simazine > desethylatrazine (DEA). After the application, the herbicides were only found in the first 40 cm of the soil during the dry period of the cultivation. They were dragged towards the depth by percolation water mainly during the first water infiltrations when the drains were set in again in autumn or winter. The losses of herbicides after the cultivation cycle (october) expressed as a ratio of the initial input ranged from 40 to 73 for the atrazine and from 40 to 44 for the simazine and depended on the importance of the application amount. In autumn and winter, the losses originating in percolation were higher than those due to volatilization and/or degradation (abiotic and biodegradation), as the soil conditions were unpropicious to the formation of non-extractable residues. References: 26
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