BEHAVIOR OF PENDIMETHALIN IN TROPICAL AND MEDITERRANEAN PLAIN FIELD CONDITION

Behaviour of the herbicide pendimethalin [N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine] was evaluated in plain field under wet tropical conditions (Martinique, FWI) and in the Mediterranean area (Languedoc, South of France). Simultaneously, adsorption parameters were discussed with Freundlich equation, and desorption evaluated using a model with two compartments corresponding to two different energy levels. Pendimethalin showed a strong adsorption in all three soils and was very difficult to desorb. Higher clay content in tropical vertisol and ferrisol involved adsorption parameters (Kfa) higher than the one found in the Mediterranean fluvisol. Although heavy rainfalls in the tropics intervene on migration, pendimethalin propensity to leaching is levelled by its strong adsorption potential and appears very limited under the conditions chosen during this work. Half-life of the compound (in the 0-25 cm soil layer) varied from 13 to 17 days. Pendimethalin was also classified as a ''nonleacher'' compound using the ''Gustafson model''.