The different soil management systems affects herbicide persistence and change the biological activity, crop selectivity and potencial to environmental risk. An experiment was carried out at the Universidade Federal do Rio Grande do Sul, with the objective of evaluating the persistence of the acetochlor herbicide on tillage and conventional tillage systems with and without straw mulch on soil surface. The soil is classified as Paleudult, and the herbicide dosis sprayed was 5040 g ha-1. The persistence of acetochlor herbicide was evaluated in a biossay, using wheat (Triticum aestivun L.) as test plant. Assessements included plant height. The acetochlor herbicide half-life was 29 and 30 day on straw mulch presence, and 18 e 16 days on straw mulch absence at the conventional tillage and no-tillage systems, respectively. Straw mulch increased acetochlor herbicide persistence in the soil.
bioassay; no tillage; conventional tillage
