Floristic analysis of weeds in organic production

The aim of this study is analysis of weed flora in organic production in open area and point to the most common weed species that threaten the crop with his presence. During the years of weed flora research in organic agriculture (lettuce, soybeans, wheat, corn, buckwheat, cabbage, carrots, onion) a total of 55 weed species are recorded. Only species Equisetum arvense belongs to the phylum Equisetophyta (Horsetail) while all other species are included in phylum Magnoliophyta (Angiosperms), of which 47 weeds belong to the broadleaf weeds (the class of Magnoliopsida - dicotyledons), and 7 weeds (all from the family Poaceae) belong to the narrow-leaved (the class of Liliopsida - monocotyledons). Recorded weed species were classified into 7 subclasses, 14 orders, 22 families and 44 genera. The weeds of the family Asteraceae and Poaceae are the most common. The analysis of life forms of the pre- sent weeds indicates on terophytic character of analyzed weed flora with a significant dominance of T4 therophytes. Geophytes and hemicryptophytes are significantly less present. The largest number of plants belong to weed-ruderal and segetal weeds. Ruderal weeds are presented by 5 species while weeds of pastures and meadows are present with only one species - Cuscuta europea. The largest number of the identified weeds blooms from June to September. Only Stellaria media blooms throughout the year. In the analyzed weed flora, there were 8 weeds are characterized as invasive species in the region of Vojvodina, as follows: Amarantus blitoides, Amarantus retroflexus, Ambrosia artemisiifolia, Datura stramonium, Galinsoga parviflora, Panicum crusgalli, Portulaca oleracea and Sorghum halepense. On basis of the floristic research of weed flora conducted for a longer period of time, it was determined that in organic agriculture the most common weeds found in different crops are: Amarantus retroflexus, Chenopodium album, Polygonum lapathifolium, Hibiscus trionum, Ambrosia artemisiifolia, Cirsium arvense, Convolvulus arvensis, Datura stramonium, Solanum nigrum and Sorghum halepense are the most present in weed flora in organic agriculture.