Effect of sunflower planting densities and sowing date for redroot pigweed (Amaranthus retroflexus) and note weed (Convolvulus arvensis) management

Using integrated weed management is a fundamental in order to management of Sustainable agricultural system this is prerequisite to have aprecise knowleage from ecological aspects of competition between weed and crops. In order to evaluate effect planting densities and sowing deat sunflower in population and biomass weed commonly in fild located karaj. a field experiment was conduction as split plot desing in complete block desing with for replication on seed and plant improvement Institute (SPII),Karaj,Iran, during 2006. Main plots consisted of four sowing date (may 30 th Jun 20 th Jul 11 th Jul 31 th) while four planting densities (6, 8, 10, and 12 plants/m2) were chosen and layed out as sub the experiment. The result showed that sowing dateat stage growing was negligible on population Amaranthus, Convolvulus and biomass Amaranthus, while at stage generation was significantly on population and biomass Amaranthus and Convolvulus, although factor planting densities was negligible on population and biomass, but was significantly on population and biomass Convolvulus. Effect planting densities at stage generation was significantly both weeds. Effect interaction planting densities and sowing date was negligible on population and biomass both weeds, but at stage generation was significantly both weeds population and biomass. The first planting date (i.e. 30 May) with 12 plants/m2 and the latest planting date (i.e. 31 July) with 6 plants/m2 produced the lowest society (6.25 no. per m-2) forredroot pigweed, (14 no. per m-2) for note weed and the highest society (12.75 no. per m-2), for red root pigweed, (17.25 no. per m-2) for note weed were respectively.