Effect Of Rotation With Cress On Yield And Soil Microbial Communities Of Continuous Cropped Cucumber

Cucumber(Cucumis Sativas L.)with high yield and economic value is cultivated in most parts of the world.However,continuous cropping has caused sever loss in its production through increase in disease incidences and affecting soil health.Paddy-upland rotation is an effective measure to alleviate continuous cropping obstacle,however,the mechanism is not clear yet.Besides,more research has focused on rotation with paddy,the crop rotation among vegetable is less reported.Here,we used cucumber and cress as crop materials in greenhouse pot experiment with five treatments as:(a)cucumber-cucumber(b)cress(flood cultivation)-cress(flood cultivation)-cucumber(c)cress(flood cultivation)-cucumber(d)cress(wet cultivation)-cress(wet cultivation)-cucumber(e)cress(wet cultivation)-cucumber,and studied the effects of cress rotation with cucumber on cucumber biomass,yield,soil physiochemical properties and soil microbial community composition.Then,we inoculated cucumber with Fusarium oxysporum f.sp.cucumerinum to clarify the effect of cress rotation on cucumber fusarium wilt.A plant-soil feedback experiment was conducted to explore the effect of changes in soil microbial communities on cucumber seedlings.Here,we also explored the influence of wet and flood irrigations on cucumber continuous cropping obstacles.The series of experiments were supposed to provide a new rotation mode of cucumber cultivation and a theoretical and technical basis to tackle the continuous cropped cucumber problem.The main results are as follow:1.Rotation with once and twice cress wet and once cress flood increased the cucumber plant biomass and yield and decrease the disease index at 20 and 30 days.2.Rotation with once and twice cress flood increased soil bulk at 0-20 cm soil layer while decreased the soil EC value at 10-20 cm soil layer.with twice cress flood and wet increased the NO3--N at 0-20 cm soil layer.Rotation with once cress flood and wet increased the soil pH at 10-20 cm soil layer and decreased the soil EC value at 0-10 cm soil layer.Once and twice cress wet increased the Olsen P at 0-10 cm soil layer.3.Rotation with once and twice cress flood and wet rotation increased soil bacterial community abundance,which was higher in once cress flood rotation than twice.Twice cress wet and flood rotation increased the soil fungal community abundance,while once cress wet and flood decreased.4.Rotation with once and twice cress wet rotation increased the bacterial and fungal diversity.Soil properties have positive correlation with bacterial community at 0-10 cm soil layer and fungal community at 10-20 cm soil layer including NO3--N and Olsen P.At phylum level,once and twice cress wet and once cress flood rotation increased the relative abundance of Cyanobacteria,Actinobacteria and Firmicutes,respectively,and increased the relative abundance of Gemmatimonadetes.Once and twice cress flood and wet rotation decreased the relative abundance of Amycolatopsis,Mycobacterium,Aeromicrobium,Kribbella and Streptomyces belonging to Actinobacteria.Twice cress flood rotation increased the relative abundance of potentially beneficial bacterial genus(Rhizobium and Devosia).Twice cress wet rotation increased the relative abundance of Pseudomonas and Nitrospira spp.Once and twice flood and twice cress wet rotation increased the relative abundance of Basidiomycota.Once and twice cress wet rotation increased the relative abundance of Zygomycota and decreased that of Ascomycota.Once and twice cress wet rotation increased the relative abundance of potentially beneficial fungal genus(Pseudallescheria,Pseudaleuria,Mycothermus,Mortierella,Cryptococcus,Aspergillus,Chaetomium and Acremonium spp.)and once cress flood rotation decreased the relative abundance of potentially pathogenic genus(Monographella,Ilyonectria and Fusarium spp.).5.The soil sterilization experiment results showed that soil microbial can influence cucumber seedling growth after rotation with cress.Plant-soil feedback results showed that once and twice cress wet rotation changed the soil microbial community structure and produced positive feedback effects on cucumber growth.6.The cucumber yield,fresh and dry weight in flooded treatment were increased by 6.01%,7.37%,29.09%,respectively,while in cress treatment by 1.80%?4.82%?21.71%,respectively.Soil water content had more effect on alleviating cucumber continuous cropping obstacles than cress.In summary,cress rotation can improve the soil properties and increase the soil microbial diversity and the relative abundance of beneficial microbial communities.The rotation has also increase the cucumber biomass and yield.Besides,rotation soil moisture is related to soil microbial community structure.