This study focused on the phyto-sociological analysis of weed in sugar cane cultivated areas located in three sugar and alcohol plants in Campos dos Goytacazes in the northern State of Rio de Janeiro Brazil. Three types of relief were taken intoconsideration: lowland (plain relief with maximum altitude of 30 m), tablelands (plain relief with altitude ranging from 30 to 50 m), and slope (wavy relief, over 50 m). Two types of cultivation (cane-plant and cane rattoon) were investigated over two periods (spring-summer and autumn-winter). The weed cane-plant and cane rattoon surveys were carried out, respectively, 30 days after plantation and 30 to 45 days after harvest. Frequencies, densities and dominances (absolute and relative) were evaluated. The index of value of importance (IVI), which expresses numerically the importance of a particular species in a community, was determined through the addition of its density, frequency and dominance values expressed in percentages. A total of 95 weed species distributed in 74 genera and 30 families were identified. The most representative family was Poaceae, followed by Asteraceae, Euphorbiaceae, Malvaceae, Papilionoideae, and Amaranthaceae. Cyperus rotundus presented the highest IVI, followed by Rottboellia exaltata. In sugarcane rattoon, during spring-summer, for lowland and tablelands, C. rotundus presented the highest IVI. On the other hand, for cane-plant, during autumn-winter,R. exaltata presented the highest IVI. Considering the slope relief, Penisetum purpureum had the highest IVI. Low similarity (degree of similarity in species composition) between the areas and periods was related to different soils, distance among areas, altitude, and mainly to the different forms of management employed.
management; relief; phyto-sociology; similarity index; Saccharum sp
