Role of Soil Moisture Content in Reducing Environmental Pollution From Pesticides

The role of soil moisture content in reducing groundwater pollution from agricultural chemicals was investigated under laboratory conditions. Specifically, the effects of different soil moisture content levels on the dissipation rates of three commonly-used herbicides: atrazine, metolachlor, and metribuzin, were analyzed using a batch degradation study in the laboratory. The soil samples were taken from a sand field in southern Québec, where no herbicides had previously been applied in the past two years. Four soil moisture content treatments: 20%, 35%, 50% and a slurried condition, were simulated to represent different moisture regimes that might occur in humid regions. Our results indicate that the degradation rates of atrazine and metribuzin were higher at 35% and 50% soil moisture content than at 20% moisture content, whereas that for metolachlor remained unaffected. The half life of atrazine was found to be one week at 50% moisture content, and two weeks at 20% and 35% moisture content. In the slurried soil, the half life was measured at more than nine weeks. For metribuzin, it ranged from three to five days for the unsaturated soil conditions and about ten days for the slurried condition. The half life of metolachlor was not affected by moisture content; it was found to be about two weeks at 20%, 35%, and 50% moisture contents. Under slurried conditions, the half life was four weeks. From the results of this study, it can be concluded that a water table management system which can maintain higher levels of moisture content in the soil profile may reduce groundwater pollution from atrazine and metribuzin in the sandy soils of Québec.