The effect of time and rate of sulfosulfuron application on Bromus japonicus Thunb. control in different wheat cultivars

Japanese brome (Bromus japonicus Thumb.) is the most important winter annual grass weed in the wheat fields of Sistan & Baloochestan province. During 2013-2014 and 2014-2015 growing season at Zahak Agriculture and Natural Resources Research Station, Zabol, field experiments were conducted to investigate the effect of rate and time of sulfosulforoun application in order to control Japanese brome in different wheat cultivars. Three wheat cultivars (Hirmand, Kalak Afghani, Sistan), three stages of herbicide application (2-3 leaves, 4-5 leaves, tillering of B. japonicus) and four herbicide doses (control, 17, 22, 22 gr. ha-1) of the commercial form of Apirus 75% were arranged in a factorial experiment under a randomized completed blocks design.Japanese brome density and dry weight were measured 30 days after final herbicide application. We also evaluated biological and grain yields of wheat at harvest. In all cultivars, herbicide application at 4-5 leaves and tillering of Japanese bromeshowed the highest and lowest weed density and dry weight respectively. Based on a logistic model fitted to density data of Japanese brome, the estimated dose to 50% loss in Hirmand at tillering stage was more than labeled-recommendation dose of sulfosulforoun ( =28.3). The grain yield values in Hirmand and Kalak Afghani cultivars showed the highest and lowest in response to. Japanese bromedensity, respectively.