The study was conducted during the 2009-2010 period in six villages in the region of Plovdiv.
A total of 442,850 dka of mid-early and late potatoes were investigated, grown under different soil and climatic conditions and under different farming practices. It was found that in areas with an altitude above 1,000 m the weed associations in potato fields were not characterized by great diversity of species and Sorghum halepensis was absent. Besides, the density of the weeds was generally negligible. In the areas with an altitude from 160 m to 219 m, the structure of the weed associations was different, dominated by late spring weeds Xantium strumarium (L.), Amaranthus retroflexus (L.), Solanum nigrum (L.), Chenopodium album (L.), followed by some perennial types – primary root and root-sprout. Sorghum halepensis (L.) pers. occurs in all investigated areas. Its density, expressed in an adjusted score, ranges from 0.20 to 0.96.