Estimativas, pelo método biológico, da sorção, lixiviação e de doses do diuron em diferentes solos

Diuron is a herbicide registered in Brazil for the control of several weed species in various crops of economic importance, such as cotton, sugarcane, banana, cocoa, coffee, citrus, eucalyptus, among others. It has long persistence in the soil and is recommended for use in pre-emergence of weeds. The selectivity of diuron for most crops, especially cotton, is due to the positioning of its molecule in the soil profile. As a result, it is a necessary condition to make safe recommendations of this herbicide, from the agronomic and environmental point of view, to know the interactions of its molecule with the soil matrix to define as recommended doses. In the literature there are reports of studies of diuron sorption and leaching in different soils. However, it is not common to make correlation between the data obtained and recommended doses, regarding the efficiency in weed control, crop selectivity and environmental risk. This research aimed to estimate, by biological method, the sorption, leaching and doses of the diuron to be recommended for weed control in different soils. Experiments were carried out to evaluate the diuron behavior in soils (sorption and leaching) and to define diuron doses for each soil that promote a control of 80% of weeds. Correlation analyses were performed between soil physicochemical attributes and diuron sorption ratio with doses that efficiently control weed species. The indicator species in the sorption and leaching experiments was Cucumis sativus. Amaranthus hybridus and Eleusine indica were used in the control efficiency experiment. Diuron sorption was higher in soils with higher organic matter contents. The diuron did not present leaching potential in any of the soil samples and the doses necessary to obtain efficient control of weed species were lower than those recommended in bulla. As doses were positively correlated with the organic matter content, CTC and sorption parameters. However, correlation analysis showed that only the correlations between soil attributes and sorption parameters do not allow efficiently determining how diuron doses to be recommended. Knowing the characteristics of the soil is a determining condition before recommending diuron doses to obtain satisfactory control of weeds with low risk of environmental contamination (contamination of soil profile and groundwater and surface water). Keywords: 1-(3,4-dichlorophenyl)-3-methyllurea. Environmental impact.