Three field studies were carried out on a silty clay soil - Haplaquoll (Molic Gleysol), during the 1996/99 season, at Epagri/Itajaí Experimental Station in southern Brazil, 26(0) 56' 35s S and 48(0) 45' 37s W, to evaluate clomazone persistence in soil and water. Clomazone 500 EC (1996/97) and 360 CS (1997/98 and 1998/99) was applied in the water in post emergence of pre-germinated seed in flooded rice area. Herbicide concentration in the soil and water was quantified before and after spraying, through several samples of water and soil taken up to rice harvesting time and analyzed with gas chromatography. In the first year, clomazone formulation 500 CE was not detected either in soil or water after 8 and 32 days after application (DAA), respectively. In 1996/97, about 3% of the amount applied remained in the paddy water by 16 DAA. In the following years, clomazone residue was detected in water up to 24 DAA. Clomazone residue levels in soil were below detectable levels after 4 and 16 DAA, in 1997/98 and 98/99, respectively. The results show that after applying clomazone (formulations EC and CS) in the water, growers should hold the water in the fields during 3 to 4 weeks, without any outflow of the pesticide treated water to waterways, otherwise superficial water could be contaminated.
dissipation; residue; pre-germinated system
