-A phyto-sociological survey is the first step to implement integrated weed management in crops. In this study, weed occurrence was evaluated in cassava plantations in the savannah of Roraima in northern Brazil. Harvest was performed randomly 80 times in 10 crops over four seasons (January, February, March, and April 2012). The harvested plants were cut at ground level, sorted out per species, identified, quantified, and weighed on a 0.01 g precision scale. A descriptive analysis was conducted of the phyto-sociological parameters (frequency, density, abundance, total number of individuals per species, relative frequency, relative density, relative abundance and importance value index) for the collected species. A description was also made of the botanical classes, families, species, type of propagation, life cycle, growth habit, total number of species and dry weight ha -1. The community in the surveyed area was considered to have a heterogeneous composition, comprising 27 species. The species presenting the highest density per hectare were Digitaria sanguinalis (210,500), Brachiaria brizantha (111,000), Brachiaria decumbens (86,500) and Brachiaria humidicola (69,000). Digitaria sanguinalis had the highest relative density (28.08), relative abundance (26.16) and importance value index (65,34). Most weeds had herbaceous growth habit.Keywords: Manihot esculenta Crantz, weeds, phytosocial study, savannah, morphological characteristics.
RESUMO -O levantamento fitossociológico é o primeiro passo para implantação do manejo integrado das plantas daninhas em culturas. Neste trabalho, objetivou-se avaliar a ocorrência de plantas daninhas em plantios de mandioca na savana de Roraima. As coletas das plantas foram realizadas aleatoriamente 80 vezes em 10 lavouras, em quatro épocas (janeiro, fevereiro, março e abril de 2012). As plantas coletadas foram cortadas ao nível do solo e, depois disso
