Influence of rice management system on propanil and 3,4-dichloroaniline behaviour in paddy field water and sediment

This study, carried out in 2004 and 2005 at Vercelli (north-west of Italy), was aimed at investigating the behavior of propanil and its metabolite 3,4-dichloroaniline in water and sediment of rice fields managed, since the year 2002, according to the following different cultivation systems: A) straw and liquid manure incorporated in autumn and rice seeded in flooded field, B) straw incorporated in autumn and rice seeded in flooded field, C) straw incorporated in autumn and rice seeded in dry field and conventionally flooded at rice tillering stage. Propanil was applied at 4.8 kg a.i. ha-1 2 days after plot draining in treatments A) and B) and in dry soil in treatment C). Five to nine days after treatment all plots were submerged. Soil sediment and water samples were collected before, immediately and at several time intervals for up to 67 days after treatment (DAT). The detection limits for propanil and 3,4 dichloroaniline were 0.02 mg kg-1 in sediment and 0.1 µg L-1 in water. Propanil was no longer detectable after 21 (sediment) and 52 DAT (water), in 2004, and 28 (sediment) and 21 DAT (water) in 2005. 3,4 dichloraniline was no longer detectable after 21 (sediment) and 67 DAT (water), in 2004, and 28 (sediment) and 52 DAT (water) in 2005. The management systems had not a clear effect on dissipation pattern of both chemicals, mainly because of the high dissipation rates showed by both chemicals during the very first days after the treatment.