Agronomie 24 (2004) 473-479
DOI: 10.1051/agro:2004043

Dissipation of pretilachlor in paddy water and sediment

Francesco Vidotto^a, Aldo Ferrero^a, Oriana Bertoia^a, Mara Gennari^b and Alessandro Cignetti<sup>c

a</sup>  Dipartimento di Agronomia, Selvicoltura e Gestione del Territorio, Università di Torino, Via Leonardo da Vinci, 44-10095 Grugliasco (TO), Italy
^b  Dipartimento di Scienze agronomiche, Agrochimiche e delle Produzioni animali, Sezione di Scienze agrochimiche, Università di Catania, Via S. Sofia, 98-95123 Catania (CT), Italy
^c  Dipartimento di Valorizzazione e Protezione delle Risorse Agroforestali, Settore di Chimica agraria, Università di Torino, Via Leonardo da Vinci, 44-10095 Grugliasco (TO), Italy

(Received 3 March 2004; accepted 28 May 2004)

Abstract - A two-year field study (2001-2002) was carried out in N-W Italy to study the behaviour of pretilachlor [2-chloro-2,6-diethyl-N-(2-propoxyethyl)acetanilide] in water and sediment of a rice field. Pretilachlor is a selective pre-emergence herbicide which is effective against annual grasses, sedges and broad-leaved weeds. The herbicide was applied in pre-seeding on a flooded rice field where water circulation was stopped for about 3 weeks after treatment. Pretilachlor concentration in the paddy water decreased by more than 90% during the first three weeks after the treatment. The amount of the herbicide in the paddy water gradually fell to levels below the sensitivity of the analytical method when water circulation was re-established. The pretilachlor concentration in the sediment gradually increased after the treatment, reaching the highest value 5 to 6 days later. The average DT₅₀ in water and sediment were 6.77 and 28.76 days in 2001, 4.68 and 15.01 days in 2002, respectively. The low percolation rate (0.95 and 0.79 mm day^-1 in 2001 and 2002, respectively) and the high ratio of the herbicide adsorption on the sediment suggest that pretilachlor disappearance from the water was mainly the result of degradation.

Key words: rice / environmental fate

Corresponding author: Francesco Vidotto francesco.vidotto@unito.it

© INRA, EDP Sciences 2004