The plant residues are the main part of the no-tillage system. Although the coverage reduces weed population density, they might intercept herbicides when applied on the mulch. Field experiments, bioassays and chromatographic analysis were made using imazaquin at the rates: zero, 75, 150 and 300 g/ha applied on 7000 and 14000 kg/ha of oat residues and on soil without mulch. Soil and straw samples were collected immediately after imazaquin application. Twenty four hours after imazaquin application the field was irrigated and more samples were collected for bioassays and chromatographics analysis. The weed population were formed by Brachiaria plantaginea, Euphorbia heterophylla and Bidens pilosa. Before irrigation, the oat residues intercepted approximately 90% from 7000 to 14000 kg/ha. Imazaquin has a great chance to be used in no-till system.
Herbicides; chromatography; residues