The main advantage of sorghum cultivation consists in its resistance to difficult thermal and moisture conditions during vegetation, especially in summer. Sorghum is planted in wide rows, and is characterized by a slow initial growth, which makes it subjected to segetal weed competition in the early stages of its development, especially under organic management system. The aim of the study was to evaluate the diversity of species of segetal flora and the effectiveness of the selected methods of mechanical weed control in organic cultivation of sorghum, under different doses of organic fertilization. A field experiment was conducted in the years 2011-2013, by crossed subblock method, in four replications. Two doses of organic fertilizer were used (20 and 40 t·ha-1) and 3 methods of mechanical crop treatment: A-control treatment (without weed control), B-with a 3-time use of a brush weeder during the season, C-with a 3-times use of a weeding hoe during the season, D-with a 2-time use of a brush weeder during the season and 1-time a hiller. The study shows that the greatest abundance and species richness of segetal flora characterized sorghum crops without applying any treatments whereas the mechanical treatment of intercrops contributed to a significant reduction in weight and number of weeds. The most effective method involved the use of a brush weeder and a hiller, which limited weed infestation on average by 75%. The efficiency of a weeding hoe and a brush weeder used alone was lower and amounted to, respectively, 58 and 51%. In all of the years of the studies, the most aggressive weed species were: Echinochloa crus-galli and Chenopodium album. The dose of organic fertilizer did not significantly affect the number and species composition of segetal flora.