ABSTRACT
Soil column field lysimeters of undisturbed soils are as close to natural field conditions as we can safely get using 14C-labeled pesticides. Tritium mobility studies showed that water moved horizontally down the soil cores. R. Kubiak et al. studied the movement of several herbicides through column lysimeters and found herbicide distribution through disturbed and undisturbed soil profiles to be relatively similar. Water input on the lysimeters was approximately 25% above the 10-year average for the 1988 and 1989 seasons. Mean annual rainfall for the area is 107 cm and annual runoff ranges from 3 to 18 cm. Since the lysimeters were installed with a 3-cm lip, allowing for no runoff, the amount of water that infiltrated was also from 2 to 17% above normal. Bermuda sod-covered lysimeters reduced C-metolachlor in the soil by 33% compared with fallow lysimeters and wheat straw-mulched lysimeters increased herbicide mobility by 7% compared with fallow lysimeters.
