Reproduction allocation and potential mechanism of individual allelopathic rice plants in the presence of competing barnyardgrass

BACKGROUND: In spite of increasing knowledge of allelopathic rice as an efficient component involved in paddy weed management, relatively little is known about its reproduction in response to competing weeds. Reproduction allocation of individual allelopathic rice plants in relation to monoculture and mixed culture with competing barnyardgrass in a paddy field was studied, along with analyses of soil nutrients and microbial communities to understand the potential mechanism. RESULTS: At a 1:1 barnyardgrass and rice mixture proportion identified from a replacement series study, biomass, grain yield and major parameters of individual allelopathic rice plants at the mature stage were increased by competing barnyardgrass. There was no difference in allelopathic rice root‐zone soil ammonium N and Olsen P between monoculture and mixed culture. However, mixed culture altered soil microbial biomass C and communities. When mixed with barnyardgrass, allelopathic rice root zone had an 87% increase in soil microbial biomass C. Phospholipid fatty acid (PLFA) profiling indicated that the signature lipid biomarkers of bacteria, actinobacteria and fungi were affected by mixed culture. Principal component analysis clearly identified differences in the composition of PLFA in different soil samples. CONCLUSION: Allelopathic rice specific changes in soil microbial communities may generate a positive feedback on its own growth and reproduction in the presence of competing barnyardgrass in a given paddy system. Copyright © 2012 Society of Chemical Industry