survey of composition and abundance of weeds in irrigated wheat (triticum aestivum l.) fields in south khorasan province

the present study was conducted to quantify the density and abundance of weeds in wheat fields of south khorasan province during 2010 and 56 species of weed form 16 plant families were identified in 240 farms of eight towns around this province. the most families in number of species were pertaining to poaceae, asteraceae and chenopodiaceae with 15 (26.79%), nine (16.7%), six (10.71%) and six (10.71%) species, respectively. the most frequencies were related to yarrow (achilla biberstinii l.) by 37.38% from the asteraceae family, hoary cress (cardaria draba l. (form bressicaseae family by 28.3% and common lambsquarters (chenopodium album l.) from chenopodiaseae family by 37.47%. hoary cress, common lambs quarters, bermuda grass (cynodon dactylon l.), camelthorn and prostrate knotweed (polygonum aviculare l.) were allocated the highest average density of the weeds with 1.38, 1.31, 1.29, 1.27 and 1.04 plant.m-2, respectively. the most abundant of weeds were camelthorn, common lambsquarters and yarrow. the highest and the lowest diversity were related to qaen city with 29 species and birjand city with 13 species, respectively.