MOBILITY OF AGROCHEMICALS THROUGH SOIL FROM 2 TILLAGE SYSTEMS

The fate of agrochemicals is often greatly affected by the surface soil conditions in the field. This study was conducted to characterize the impact of two contrasting tillage systems on the movement of agrochemicals in soil. The two tillage systems were plow-tillage (PT) and no-tillage (NT) for corn (Zea mays L.) production. The study included incubation and leaching of undisturbed soil columns and disturbed soil samples from 16-yr plots subject to the two tillage regimes. The agrochemicals used in the study were NH4NO3, atrazine (2-chloro-4-thylamino-6-isopropylamino-1,3,5-triazine-2,4 diamine), carbofuran (2,3-dihydro-2,2-dimethyl-7-benzofuranyl methylcarbamate), diazinon (0,0- diethyl-O-(6-methyl- 2(1-methethyl)-4-pryamidinyl phosphor- othioate), and metolachlor (2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-metoxy-1-methylethyl) acetamide). The results of this study show greater ponded flow movement of all agrochemicals in soils under PT vs. NT conditions. Strong evidence was found for preferential flow through the soil, with the chemicals by-passing much of the soil-matrix under recently plowed soils as well as NT soils. Nitrate leaching was significantly greater under PT than NT, apparently due to greater mineralizing activity of the PT soil compared with the NT soil. The pesticide movement also tended to be greater under PT than NT. Caution should be exercised in generalizing to field conditions, but these data suggest that there can be greater leaching losses of surface-applied agrochemicals to groundwater under PT than under NT.