factors affecting the population density of weeds and yield loss of them in wheat: a case study in golestan province – bandargaz

to investigate the factors affecting the population density of weeds and yield loss of them in wheat, a non systematic survey experiment was conducted in 45 fields in the township of bandar-gaz (sarmahaleh village) in 2012. sampling of wheat and weeds were taken in two stages (heading and harvest maturity) by randomized to the five points of each field using quadrate size 1m*1m. in this study all information about crop management including land area , farmers experience , the seed bed preparation, sowing date , cultivar and site preparation of them, sowing ways , seed rate , weeds control ways , kind , amount and time of herbicide , fungicide use and wheat harvest time were collected during a growing season by preparing questionnaire and complete them with farmers. at the end of the growing season, the actual yield harvested by farmers’ ‬ recorded. among the various parameters, wheat plant and raceme density, farmer experience, kind of variety and use of tapic+geranestar herbicide had significant effects on weed population. with increased wheat plant density, weed density decreased. also there was less weed density in field of high experience farmer. weed density was lesser in n8118 variety than n8019 variety and not use tapic+granestar herbicide due to increased of weeds density. among weed different species, avena sp, phalaris minor and sinapis arvense had highest negative effect on wheat yield. model study showed if wheat plant density was optimum and there were weeds, yield will be 2713kg/ha and if weeds remove yield will increase to 2877kg/ha (yield gap equal164kg/ha). amaong weed, phalaris minor (12 plant per m-2), sinapis arvensis (3plant per m-2) and avena sp (2 plant per m-2) with 65, 18 and 17% yield loss respectively, were the strongest competitor with wheat.