Population indices of wild barley (Hordeum spontaneum Koch.) in wheat fields

A study was conducted from 2013 and 2014 to assess the changes of population indices of wild barley (Hordeum spontaneum Koch.) in different wheat fields (including: Tehran, Alborz, West Azarbaijan, Isfahan, Kermanshah, Khuzestan and Fars provinces). First, the fields that had been evaluated in the past years (2003) were selected and second field selection was based on the wheat cultivated area in any city and the new fields were evaluated and selected (2013). Using the existing equations, the frequency, uniformity and mean density of this species were calculated. Finally, the map of the spatial distribution of wild barley for each province was produced using Geographic Information System (GIS). The results showed that frequency and uniformity of wild barley in wheat fields of provinces that had lower populations of this weed in the past years, greatly had been enhanced (Alborz and West Azarbaijan). But in the wheat fields of provinces that wild barley was more populated in the past years, mean density increased (Tehran, Fars and Khuzestan). Distribution of the wild barley in the wheat fields were dependent on the numerous factors including seed longevity, distribution mechanisms and competition reproductive characteristics, that all these factors have caused this species spread in different regions of Iran. Another success factors of the spread of this weed is drought. Continuous wheat cropping (monoculture) and plowing in dry soil in autumn in wheat fields due to late rains and continuous application of Accase inhibitors herbicides that does not control this weed in wheat fields, can be effective in expanding wild barley.