the reaction of kochia (kochia scoparia) ecotypes to sowing date in mashhad weather condition

kochia is one of those plants which have capability to grow in different environments and can be used as a valuable plant to produce biomass and seed. the purpose of this study was to evaluate the possibility of kochia planting in different dates as well as its resistance to cold weather of mashhad winter. seven sowing dates including 10th october, november, march, april, may, june and july and three iranian kochia ecotypes including birjand, sabzevar and borujerd were considered as main and sub plots, respectively, in a split plot design based on crdb with three replications. results showed that those planted on september and october died due to the cold weather of autumn and winter. plant height, shoot yield and biological yield were decreased due to the delayed planting after march. birjand ecotype produced the highest plant compared to the other ecotypes, but there was no significant difference among ecotypes according to shoot yield. also, biological yield in sabzevar ecotypes was significantly higher than other ecotypes. seed yield at those planted on april was higher than other planting dates but there were no significant differences in seed yield among the other ecotypes. the highest and lowest harvest index obtained at those planted on june and march, respectively. generally, results showed that kochia could not tolerate mashhad winter condition but could be planted after march.