Organoclay-based formulations to reduce the environmental impact of the herbicide diuron in olive groves

Ground and surface water contamination caused by undesirable transport losses of herbicides commonly applied to olive (Olea Europaea) groves in Spain and other Mediterranean countries is demanding strategies to reduce the environmental impact of such herbicides. In this work, organoclay-based formulations of a herbicide widely applied to olive groves, diuron [3-(3,4-dichlorophenyl)-l,l-dimethyl urea], were prepared by preadsorbing the herbicide on three organoclays. Then, the ability of the organoclay-based formulations to reduce the herbicide release rate and leaching potential in two soils as compared to a standard commercial formulation of the herbicide was assessed. The organoclays were obtained by treating Wyoming montmorillonite (SWy-2) and Arizona montmorillonite (SAz-1) with an amount of spermine (SPERM) or hexadecyltrimethylammonium (HDTMA) cations equal to 100% of the cation exchange capacity of the montmorillonites. Batch release and column leaching tests indicated that the organoclay-based formulations of diuron made the release of the herbicide slower and reduced its leaching potential in soils, as compared with a standard commercial formulation containing the herbicide in a readily available form. Soil incubation experiments revealed that the persistence of the herbicide applied to soil as organoclay-based formulations was only slightly prolonged compared with the herbicide applied in a readily available form, and that most herbicide in the formulations was ultimately available for degradation. The use of organoclay-based formulations is proposed as a strategy to reduce extensive transport losses associated with the application of diuron in high-risk scenarios, such as Mediterranean olive groves.This work has been financed by the Spanish Ministry of Education and Science, with FEDER funds, through the projects AGL2005-05063-C02-01 and AGL2008-04031-C02-01. C. Trigo also thanks the Spanish Ministry of Education and Science for her FPI fellowship (ref. BES-2006-14099).Peer Reviewe