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(W/FF220) Slow release formulations of the herbicide hexazinone based on inorganic and organic clays. Celis, Rafael1, Escalona, María1, Carrizosa, María1, Hermosín, María1, Cornejo, Juan1, 1 ABSTRACT- The environmental problems associated with pesticide use, in particular highly mobile pesticides, is a concern because of the increasing presence of these agrochemicals in surface and ground waters. An approach for minimizing pesticide transport losses is to enhance the soil sorption process, for instance through the application of the pesticide incorporated or sorbed on a matrix or carrier, which limits the amount of pesticide available for those undesirable losses. In this work, Fe3+-montmorillonite (Fe-SWy) and hexadecyltrimethylammonium-montmorillonite (HDTMA-SWy) were mixed with the herbicide hexazinone in three different ways and the resulting complexes were assayed as slow release formulations of this highly mobile herbicide. The release profiles of hexazinone in water showed that all formulations based on Fe-SWy and HDTMA-SWy behaved as slow release formulations with an initial hexazinone release from 10 to 60% and a final release from 20 to 90% after 7 days. This was in contrast to the instantaneous release of 100% of the herbicide from the commercial formulation, used as a reference. The leaching profiles of commercial and clay formulations were compared using hand-packed soil columns. All clay formulations led to lower hexazinone concentrations in the leachates and, in the case of HDTMA-SWy, to later breakthrough of the herbicide, thus reducing the risk of ground water contamination. Bioassays were also carried out and indicated that hexazinone formulations prepared from Fe-SWy and HDTMA-SWy were as effective as the commercial formulation in the control of weeds (Lepidium sativum) at the usual application rate for hexazinone of 10 kg/ha. Key words: controlled release, herbicide, leaching, organoclay |
