AbstractBACKGROUNDDespite increasing knowledge of allelopathic rice interference with barnyardgrass, relatively little is known about its action on herbicide‐resistant barnyardgrass. The incidence of herbicide‐resistant barnyardgrass is escalating in paddy fields. Knowledge of the interference of allelopathic rice with herbicide‐resistant barnyardgrass and the potential mechanisms involved is warranted.RESULTSPenoxsulam‐resistant and ‐susceptible barnyardgrass biotypes were identified and segregated from a putative penoxsulam‐resistant population occurring in paddy fields in China. Allelopathic rice inhibited the growth of barnyardgrass roots more than shoots, regardless of biotype. In particular, there was a stronger inhibition for resistant barnyardgrass than for susceptible barnyardgrass. Allelopathic rice significantly reduced total root length, total root area, maximum root amplitude and maximum root depth in barnyardgrass. Furthermore, the rice allelochemicals tricin and momilactone B inhibited the growth of both resistant and susceptible barnyardgrass. Compared with root contact, root segregation significantly increased inhibition of barnyardgrass with an increase in rice allelochemicals. Root exudates from barnyardgrass induced the production of rice allelochemicals, but the effect of susceptible barnyardgrass was much stronger than that of resistant barnyardgrass.CONCLUSIONAllelopathic rice can interfere with the growth of penoxsulam‐resistant barnyardgrass through allelochemical‐mediated root interactions. This type of allelopathic interference may provide a non‐herbicidal alternative for herbicide‐resistant weed management in paddy systems. © 2017 Society of Chemical Industry