The cultivation and deposition of cover crops residues on the soil surface can reduce weed emergence. The objective of this study was to evaluate the emergence of weeds, in a greenhouse, on a soil with cover crops in an agroecological no-tillage system. The experiment was conducted in a greenhouse with soil samples from an experiment installed in Ituporanga (Santa Catarina state). On April 2010 and 2011, the following field treatments were implemented: weed vegetation (VE), Hordeum vulgare (2010)/Avena strigosa (2011) (CV/AV), Secale cereale (CE), Raphanus sativus (NF), Secale cereale + Raphanus sativus (NF+CE) and Hordeum vulgare/Avena strigosa + Raphanus sativus (NF+AV). After the rotation of the species, the soil samples were collected in July. The identification of the species and the emergence assessment occurred 15, 30, 45, 60, 75, 90 and 105 days after the beginning of the experiment. The species with the highest incidence were: Amaranthus lividus, Oxalis spp., Cyperus spp., Stachys arvensis, Cynodon spp. and Rumex obtusifolius. Residues from single species of Secale cereale, Avena strigosa and Hordeum vulgare have shown the greatest ability to suppress weeds during the first 45 evaluation days; this corresponds to the beginning of the critical period in the onion development.
green manuring; seed bank; Allium cepa