The aim of this work was to identify the occurrence of weeds after five years of no-tillage corn cultivation in the Amazonian savannah. A phytosociological survey was conducted involving collection, identification, and quantification of the weeds, after corn harvest during June and July, 2010. The investigated properties included botanical classes, families, species, number of individuals, frequency, density, abundance, relative frequency, relative density, relative abundance, importance value index, propagation method, and life cycle. The emergent vegetation in the study area had 419species, nine of which were identified as Dicotyledons, while six were identified as Monocotyledons. Species in the Ciperaceae family were the most abundant, while the families Poaceae, Ciperaceae, Asteraceae, Malvaceae, and Fabaceae exhibited the highest number of individuals and species frequency per plot. Only the Cordia curassavica shrubby growth habit was identified. Cyperus rotundus species showed the highest values in all the phytosociological parameters evaluated, with an importance index value 1.5 times higher than that of Brachiaria humidicola which had the second highest value (40.49).
Roraima savannah; vegetation cover; crop rotation; Zea mays
