Journal on Processing and Energy in Agriculture 17 (2013) 1 33 Biblid: 1821-4487 (2013) 17; 1; p 33-38 Original Scientific Paper UDK: 632.51 Originalni naučni rad FLORISTIC ANALYSIS OF WEEDS IN ORGANIC PRODUCTION FLORISTIČKA ANALIZA KOROVA U ORGANSKOJ PROIZVODNJI Branka LJEVNAIĆ-MAŠIĆ, Dejana DŽIGURSKI, Ljiljana NIKOLIĆ University of Novi Sad, Faculty of Agriculture, 21000 Novi Sad,Trg Dositeja Obradovića 8, Serbia e-mail: brana@polj.uns.ac.rs ABSTRACT 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 ana- lyzed weed flora, there were 8 weeds are characterized as invasive species in the region of Vojvodina, as follows: Amarantus bli- toides, Amarantus retroflexus, Ambrosia artemisiifolia, Datura stramonium, Galinsoga parviflora, Panicum crus-galli, Portulaca oleracea and Sorghum halepense. On basis of the floristic research of weed flora conducted for a longer period of time, it was deter- mined 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. Key words: flora, floristic analysis, invasive species, weeds, organic production. REZIME Cilj rada je da se, na osnovu višegodišnjih florističkih istraživanja, prikaže floristička analiza korova u organskoj proizvodnji na otvorenom prostoru te da se ukaže na najčešće korovske vrste koje svojim prisustvom ugrožavaju useve. Višegodišnjim florističkim istraživanjima korova u organskoj proizvodnji (salate, soje, pšenice, kukuruza, heljde, kupusa, šargarepe, luka) konstatovano je ukupno 55 korovskih vrsta. Odeljku Equisetophyta (rastavića) pripada samo vrsta Equisetum arvense, dok su sve ostale vrste obuhvaćene odeljkom Magnoliophyta (skrivenosemenica) od čega širokolisnim korovima (klasa Magnoliopsida - dilotile) pripada 47, a uskolisnim (klasa Liliopsida - monokotile) 7 korova svi iz familije Poaceae. Zabeležene korovske vrste svrstane su u 7 podklasa, 14 redova, 22 familije i 44 roda. Najzastupljeniji su predstavnici familija Asteraceae (12 vrsta) i Poaceae (7 vrsta). Analiza životnih formi prisutnih korova ukazuje na terofitski karakter analizirane flore (76,36% - 42 vrste) sa znatnom dominacijom T 4 terofita. Geofite (16,36% - 9 vrsta) i hemikriptofite (7,28% - 4 vrste) su znatno manje prisutne. Najveći broj konstatovanih biljaka pripada korovsko-ruderalnim (61,82% - 34 vrsta) i segetalnim korovima (37,27% - 15 vrsta). Ruderalni korovi zastupljeni su sa 5 vrsta (9,09%), a zabeležen je i jedan korov pašnjaka i livada - Cuscuta europea (1,82%). Najveći broj prisutnih korova cveta od juna do septembra. Jedino Stellaria media cveta tokom cele godine. U analiziranoj korovskoj flori konstatovano je prisustvo 8 korova okarak- terisanih kao invazivne vrste za područje Vojvodine. To su: Amarantus blitoides, Amarantus retroflexus, Ambrosia artemisiifolia, Datura stramonium, Galinsoga parviflora, Panicum crus-galli, Portulaca oleracea i Sorghum halepense. Na osnovu višegodišnjih florističkih istraživanja korovske flore utvrđeno je da su najčešće korovske vrste u organskoj poljoprivredi: Amarantus retroflexus, Chenopodium album, Polygonum lapathifolium, Hibiscus trionum, Ambrosia artemisiifolia, Cirsium arvense, Convolvulus arvensis, Datura stramonium, Solanum nigrum i Sorghum halepense. Ključne reči: flora, floristička analiza, invazivne vrste, korovi, organska proizvodnja. INTRODUCTION According to the International Federation of Organic Agri- culture Movements (IFOAM) organic agriculture is a production system which sustains the health of soil, ecosystem and people, relying on ecological processes, biodiversity and cycles adapted to local conditions; it also combines tradition, innovation and science by promoting fair relationships and a good quality of life. It is based on crop rotation, using manure, compost and bio- logical pest control, while excluding or strictly limiting the us- age of synthetic fertilisers and pesticides, plant growth regula- tors, nanomaterials, etc. (Kovačević and Momirović, 2004; Lazić and Lazić, 2008; Sekulić et al., 2008; Ljevnaić-Mašić et al., 2011; Paull, 2011). Weeds are a great problem in organic agriculture as their presence leads to reduction in yields and the quality of crops. Weed species gradually adapt to the cultivated plants and to the agro-technical measures that have been applied for a long period of time. However, the aim is not to eradicate weeds completely, as it is the case in conventional agriculture, but to bring them into balance with the cultivated crop (Kovačević and Momirović, 2004). Weed control in organic agriculture is performed by: ade- quate selection of plant species and varieties, maintenance of land without weed seeds or their organs of vegetative propaga- tion, adequate crop rotation, adequate tillage, weed control using physical and mechanical measures, growing cover crops, solari- sation, pre-planting irrigation, etc. (Kovačević and Momirović, 2004; Lazić and Lazić, 2008). On the basis of the relationship