Effect And Meachanism For Earthworm To Remit Continuous Cropping Obstacle Of Strawberry

Earthworms play an important role in promoting plants growth, however, the effect of earthworm on continuous cropping plants and its mechanism which is very important for remitting continuous cropping obstacle, is not clear. In this study, the effect of earthworms on remitting the continuous cropping obstacle of strawberry was studied in greenhouse pot experiments and microcosm experiment. Meanwhile, we also elucidated the mechanisms for earthworms to remit continuous cropping obstacle through studying the effect on degradation of allelochemicals and regulation of microorganisms. The main results are as follows:(1) Earthworms can stimulate the growth, increase the biomass and yield of strawberry and decrease the disease index of Fusarium wilt significantly (P<0.05). However, the effects differed between different species. Metaphire guillemi had a better effect than Eisenia fetida (P<0.05).(2) The capicity of earthworm to degrade phenolic compounds are related with the species and density of earthworms, the source of phenolic compounds and whether the soil is sterilized. Metaphire guillemi showed higher capicity than Eisenia fetida in degradation phenolic compounds and when the density of Metaphire guillemi reached to 300 Individuals/m2, the degradation rate of phenolic compounds arrived at its upper limit. The course of degradation phenolic compounds for earthworms needed microorganism. In addition, when earthworm involved, the phenolic compound derived from leaves degraded faster than that derived from roots.(3) Earthworms were not active to degrade phenolic compound, they avoided high concentration (120 ug p-coumaric acid) of phenolic acid. Fortunately, the avoiding behavior to phenolic acids can be offset through adding some organic matter such as strawberry leaves.(4) During the degradation of phenolic compounds, microorganisms played an important role and the presence of earthworms improved the activity and accelerated the succession of microbial community so that accelerated the degradation of phenolic compounds.(5) Earthworms showed different effects on degradation individual phenolic acids. The activities of earthworms accelerated the degradation of total phenolic compounds as well as some phenolic acids that have a relative higher concentration in soil like p-coumaric acid and chlorogenic acid, but did not show significant effects on degradation of other individual phenolic acids.(6) Earthworms have two main effects on continuous cropping strawberry plants. Firstly, earthworms regulated the microbial community and improved the activity and biodiversity of microorganism, which improved the suppressive of strawberry planted soil. Secondly, earthworm can accelerate the degradation of phenolic acids, which can stimulate pathogen, inhibit plant growth and disturb the balance of rhizosphere. Moreover, the microbial community and phenolic acids can be affected by each other. The degradation of phenolic acids benefit the recovery of soil rhizosphere and the regulated microbial community is of assistant to the degradation of phenolic acids. Above all, the comprehensive effects of earthworms result to remitting continuous cropping obstacle.