Identification and survey of weeds distribution in rainfed wheat fields of Maragheh

In order to identification and survey of weed species in rainfed wheat fields of Maragheh, sampling was done in 50 fields followed a "W" pattern by 20 quadrats 0.25 m2 for each field during the wheat tillering to stem elongation stages in spring 2018. Ranking of weeds were done with relative dominant index. Data on weeds and environmental factors of all fields were analyzed through redundancy analysis (RDA) and weed species distribution and their relationships with environmental factors displayed in ordination diagrams. Overall, 81 weeds species belonging to 20 plant families were identified in these fields. The sunflower, grasses, and mustard families with 14, 13, and 11 weed species, respectively were dominant plant families in these fields. Cow soapwort (Vaccaria grandiflora), Russian knapweed (Acroptilon repens), sticky willy (Galium aparine), and false carrot (Turgenia latifolia) with 30.45, 29.51, 26.49, and 25.30, respectively were dominant weed species. Among observed weeds, 61.73% were annual and 38.27% were perennial. Also, 83.95% of weeds were dicotyledonous and 16.05% of them were monocotyledonous. RDA was done with frequency of 60 frequent weed species (observed in more than 3 fields) and sampling sites latitude, longitude, and elevation using CANOCO (Version 4.5). RDA results showed that site latitude and then elevation had maximum effect on weed species distribution. The first and second RDA axes described 77.9% of variations in weeds distribution affected by surveyed environmental factors. Cow soapwort and Russian knapweed had maximum presence in fields with highest elevation, but Iranian knapweed (Centaurea depressa) was observed in fields with minimum elevation.