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During the 2006-2009 period, in the experimental field of the Institute of Forage Crops in Pleven a study was conducted with the purpose of determining the effect of cultural practice and weed control on the seed productivity of perennial ryegrass. As a result of the four-year study, the following conclusions were made: Perennial ryegrass is very susceptible to the weed competitive influence in the establishment year, as well as in the seed production years. The highest efficiency against the weeds was obtained by chemical control, but the use of cover crops (spring forage pea, spring barley) and mixed stands with white clover are a successful alternative practice with weed suppressive and ecological effects under the conditions of ecologically friendly agriculture. On average for the period of the study, the seed yield of perennial ryegrass exceeded that from the check of the pure stand as follows: pure stands with chemical control - by 27%; stands with cover crops and chemical control - by 20 to 32%, the same stands without chemical weed control - by 5 to 11%; mixed stands with chemical control - by 30% and without weed control - by 14%. Considerable dry biomass yield was harvested from the seed production stands of perennial ryegrass and in the establishment year the sowing of a cover crop or in a mixed stand resulted in more efficient use of the area and an yield increase by 3.7 to 13.9 times, and on average for the four-year period - by 30 to 59%. [ABSTRACT FROM AUTHOR]