In order to investigate the growth and development effects of susceptible and resistant barnyardgrass on rice,two barnyardgrass varieties( susceptible for T1 and resistant for T2) separately against quinclorac,penoxsulam and bispyribac-sodium,were employed under the co-culture condition with rice nanjing 9108 during the period from rice transplanting to maturity and with weed free as a CK. The results showed that resistant barnyardgrass significantly reduced tiller number,dry matter accumulation,spikelets p...