evaluation of replacement intercropping of soybean (glycine max l.) with sweet basil (ocimum basilicum l.) and borage (borago officinalis l.) under weed infestation

in order to evaluate intercropping of soybean (glycine max l. cv. jk) with sweet basil (ocimum basilicum l.) and borage (borago officinalis l.) with weed interference, an experiment was performed in randomized complete block design with 12 treatments and three replications at a field located 10 km of shirvan during year of 2011. the treatments were included 75% soybean: 25%sweet basil, 50%soybean: 50% sweet basil, 25% soybean: 75% sweet basil, 75% soybean: 25% borage, 50% soybean: 50% borage and 25% soybean: 75% borage under weed infestation, in addition sole cropping of plants under weed control and weed interference. intercropped plants had more success in reduction of weed density and biomass compared to monoculture. soybean50: sweet basil50, reduced the weed density by 47.95% and 52.9%, and reduced the weed biomass by 68.91% and 61.87% more than sweet basil and soybean pure stand, respectively. investigation of dry matter accumulation showed that increasing of plant proportion in intercropping caused increasing of plant dry matter. the height of soybean and borage was increased in intercropping and weed interference, while the highest height of sweet basil was observed in monoculture at second harvest. biological and economical yield of soybean in intercropping with sweet basil was higher than intercropping with borage. the highest harvest index was related to 50:50 soybean: sweet basil ratio. in this ratio, the harvest index increased 4.9% compared to soybean monoculture. yield of sweet basil and borage decreased with increasing of soybean rows in intercropping. based on area-time equivalent ratio, soybean 75% with sweet basil and borage 25% (based on borage seed yield) had 3% and 4% advantage compared to monoculture.