Abstract: In order to explore the bio-interference of allelopathic rice with barnyardgrass under different nitrogen supplies,a new bioassay method,i.e.,allelopathy-competition separation based (ACS) approach was recommended in this study.The results indicated that ACS could be successfully used to distinguish the rice allelopathy from its resources competition in rice-weed co-culture system,and to evaluate its response characteristics under different N supplies.The test rice accession PI312777 had a higher ability in interfering target weed barnyardgrass (BYD),represented by its stable and higher ability in resources competition,as well as its increasing allelopathic potential in suppressing companion weed BYD when the N supply decreased in the co-cultured system.The reverse was true in the case of rice accession Lemont,which had a lower allelopathic potential under all N supply levels,and a lower ability in resources competition under normal or rich N supply.But,Lemont had an obviously increased ability in resources competition under lower N supply,which was considered as the result of econiche competition in rice-weed system.

Key words: Oryza sativa, Allelopathy, Resources competition, Nitrogen stress, Econiche, Allelopathy-competition separation based bioassay (ACS)