ability of three legume cover crops to control weeds in corn

in order to evaluate the competitive ability of legume cover crops on interference of weeds in corn, an experiment was carried out in sari agricultural sciences and natural resources university during 2011 growing season. this research was carried out based on complete block design with three replications. treatments consisted of three cover crops including: soybean (glycine max l.), fenugreek (trigonella foenum gracu l.) and cowpea (vigna unguiculata l.) planted at two different dates (simultaneous with corn and 21 days after planting of corn), along with two controls (no weeding and weeding). in this study the competition index (ci), ability of withstand competition (awc), grain yield and morphological characteristics of corn were evaluated. the results showed significant differences in the awc and ci among the cover crops. 21 days after planting of corn for cowpea had the highest ci. at simultaneous with and 21 days after planting of fenugreek, the lowest ci (0.64 and 0.32 respectively) was observed. planting cover crops such as soybean at the simultaneous with and 21 days after planting of corn and planting cowpea after 21 days was effective in weed control and also, awc of corn was highest. generally, the results of this research showed the highest ones of 11853/13 and 11447/4 kg h-1 was achieved in control (with weeding) and the cowpea at the 21 days after planting of corn, respectively.