SORPTION OF ATRAZINE AND METOLACHLOR BY BURROWLININGS DEVELOPED IN SOILS WITH DIFFERENT CROP RESIDUES AT THE SURFACE

Abstract

Atrazine and metolachlor sorption by earthworm (Lumbricus terrestrisL.) burrows was measured by introducing herbicides into the burrows and collecting the effluent between 0 to 3, 3 to 6, and 6 to 9 min of simulated burrow flow. On average, sorption by burrow linings reduced the herbicide concentration to 78% (atrazine) and 74% (metolachlor) of the applied herbicide solution concentration. For both herbicides, the amount sorbed was dependent on the food source available to the earthworm, as well as the duration of burrow flow. On average, soybean-fed- and corn-fed-earthworm-burrows significantly retained more herbicides relative to the Control Treatment (unfed-earthworms). More herbicides were transported through the burrows with time because the lateral flow movement from the burrow wall into the soil matrix decreased. 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 between 3 to 9 min. Based on these results, we conclude that herbicide transport through earthworm burrows in the field will be related to crop and crop residue management practices.

Keywords:

• Herbicide
• Atrazine
• Metolachlor
• Earthworm burrows
• Corn residues
• Soybean residues
• Sorption
• Leaching

ACKNOWLEDGMENTS

We gratefully acknowledge the financial support of Agriculture and Agri-Food Canada and the Canada-Ontario Green Plan. The authors would also like to thank Dr. John Purdy of Novartis Crop Protection Canada Ltd. for providing the radiolabelled herbicides.