Sorption of atrazine and metolachlor by burrow linings developed in soils with different crop residues at the surface

Atrazine and metolachlor sorption by earthworm (Lumbricus terrestris L.) bu rrows was measured by introducing herbicides into the burrows and collectin g the effluent between 0 to 3, 3 to 6, and 6 to 9 min of simulated burrow f low. On average, sorption by burrow linings reduced the herbicide concentra tion to 78% (atrazine) and 74% (metolachlor) of the applied herbicide solut ion concentration. For both herbicides, the amount sorbed was dependent on the food source available to the earthworm, as well as the duration of burr ow flow. On average, soybean-fed- and corn-fed-earthworm-burrows significan tly retained more herbicides relative to the Control Treatment (unfed-earth wonns). More herbicides were transported through the burrows with time beca use the lateral flow movement from the burrow wall into the soil matrix dec reased. It is also likely that herbicides retained on burrow linings during the first 3 min of flow saturated the adsorption sites on the burrow wall, which decreased the subsequent retention potential of herbicides in flow b etween 3 to 9 min. Based on these results, we conclude that herbicide trans port through earthworm burrows in the field will be related to crop and cro p residue management practices.