effects of environmental and management factors on the weed species richness of winter crops in ilam province

this research was conducted to assess the effects of management and environmental factors on the weed species richness of winter crops in ilam province. in order to recognize the weed species, three counties were selected based on the type of climate in 2011-2012. according to the cultivated areas of winter crops in each county, 48 fields were chosen and demographic information was calculated by counting the weeds in each field. the geographic information such as altitude, longitude and elevation above sea level were recorded by gps at each location. the results showed that 35 weed species were found in wheat (main winter crop) fields. the main broad leaf weeds in wheat fields were malva neglecta, vaccaria peramidata, sinapsis arvensis, and galium tricornutum. avena ludoviciana were the most widespread grass weed species in these fields. it was found that s. arvensis and a. ludoviciana with 61.76 and 55.88 percent, respectively, had the greatest constancy on wheat fields. only crop type and planting date were effective on weed species richness among crop management variables considered in this research.