1 Effect of Soil Wetting and Drying Cycles on Metolachlor Fate in 2 Soil Applied as a Commercial or Controlled - Release 3 Formulation 4

8 A controlled-release formulation (CRF) has been developed for metolachlor, which reduced its 9 leaching in a sandy soil and improved weed control in comparison with the commercial formula10 tion. The current study tested the effect of soil wetting and drying cycles (WDCs) on metolachlor 11 fate (desorption, leaching, and weed control) applied as the CRF and as the commercial formula12 tion. Metolachlor adsorption to a heavy soil (Terra-Rosa) was predominately to the clay minerals and 13 oxides. Metolachlor release from a heavy soil subjected to WDCs was higher than its release from the 14 soil not subjected to WDCs. Consequently, a bioassay in soil columns treated with the commercial 15 formulation indicated enhanced metolachlor leaching in heavy soils under WDCs. In contrast, when 16 metolachlor was applied as the CRF, leaching was suppressed and not affected by WDCs. These 17 results emphasize the advantages of the CRF also in heavy soils subjected to WDCs.