Differences in species composition could be explained in the differences in weed management, canopy structure and resource capture among crops [31]. A group of species were common to all treatments whereas some group species were more frequent or occurred only in a particular cropping treatment (i.e. for intercrops Convolvulus arvensis L., Chenopodium album L., Verbena gracilescens (Cham.) Hert., Conium maculatum L., Cynodon dactylon (L.) Pers., Gamochaeta spicata (Lam.) Cabr., Melica argyrea Hack., Plantago lanceolata L., Poa annua L., Sorghum halepense (L.) Pers., Verbena bonariensis L. in Exp 1, Sonchus oleraceus L. Amaranthus viridis L. Conyza bonariensis (L.) Cronquist, Trifolium repens L. in Exp 2). However, species composition varied among years, probably related to differences in environmental conditions and field cropping histories.