Continuous Application Of Bio-organic Fertilizer Promoted Cucumber Yields And Altered Soil Microflora

Application of chemical fertilizer plays a vital role in improving crop yield in China.However,excessive and unscientific application is widespread,resulting in a series of ecological problems,i.e.,soil compaction,soil acidification,soil organic matter decline and water eutrophication.In order to solve these problems,research and development as well as adequate application of bio-organic fertilizer has become one of the most important area for modern agriculture.Besides,biological seedling substrate made by inoculation plant growth promoting rhinoacteria(PGPR)into seedling substrate could also significantly improve the biomass and quality of cucumber seedlings and yield after transplanted into field,which is an another important way to increase the agricultural outputs.The full paper includes three parts:the effect of continuous application of bio-organic fertilizer or biological seedling substrate containing Bacillus subtilis SQR9 on the growth and yield of cucumber in greenhouse were studied on the first part;the effects of ?-radiation sterilized bio-organic fertilizer,y-radiation sterilized bio-organic fertilizer inoculated with PGPR strain and bio-organic fertilizer on the biological characteristics of cucumber were compared on the second part;and the effects of bio-organic fertilizer continuously applied to the cucumber mono-cropped field on the microbial community of cucumber soil were explored on the last part.The following main results are obtained:1.Compared to non-fertilization control(CK),chemical(CF)and organic fertilizer(OF)application treatments,continually application of bio-organic fertilizer could significantly promote the growth of cucumber,increase the quality and yield of cucumber,and depress the number of Fusarium oxysporum in soil.The cucumber yield of each treatment for 5-seasonal experiments all ranked as BIO>OF>CF>CK according to descending order.In detail,the yield of BIO treatment for the 1st and 2nd season was significantly higher than that for CF and CK while the yield of BIO treatment for the 3rd,4th and 5th season was significantly higher than that for CK.For the 1st season,the yield of BIO treatment increased by 9.41%and 11.06%as compared to OF and CF treatment,respectively;for the 2nd season,the yield of BIO treatment increased by 3.67%and 30.63%as compared to OF and CF treatment,respectively;for the3rd season,the yield of BIO treatment increased by 7.44%and 9.63%as compared to OF and CF treatment,respectively;for the 4th season,the yield of BIO treatment increased by 9.54%and 21.91%as compared to OF and CF treatment,respectively;and for last season,the yield of BIO treatment increased by 2.54%and 2.94%as compared to OF and CF treatment,respectively.The 5-seasonal consecutive application of biological seedling substrate could effectively enhanced the colonization of PGPR strain,which could significantly promote the growth of cucumber,increase and the yield of cucumber,and depress the number of F.oxysporum in soil.Briefly,For the 1st season,the yield of treatment of organic fertilizer application after transplantation of cucumber seedling cultivated using biological seedling substrate(OFNS)increased by 2.74%compared with treatment of organic fertilizer application after transplantation of cucumber seedling cultivated without biological seedling substrate(OF)while for the 2nd,3rd,4th and 5th season,OFNS treatment increased 4.35%,5.95%,15.14%and 11.07%compared to OF treatment,respectively.During 5-seasonal experiments,OFNS treatment all significantly improved the plant height and stem diameter,enhanced the soil content of available potassium,available phosphorus,EC,TN and TP,and reduced the number of F.oxysporum in the cucumber bulk and rhizosphere soil compared to OF treatment.2.Consecutive 3-seasonal pot experiments indicated that sterilized bio-organic fertilizer inoculated with Bacillus amyloliquefaciens SQR9 which antagonized to F.oxysporum(SBIO+SQR-9)could effectively promote the growth of cucumber plants,including increasement of plant height,stem diameter and SPAD value for chlorophyll content.Meanwhile,SBIO+SQR-9 treatment significantly depressed the number of F.oxysporum and increased the number of Bacillus sp.in cucumber bulk and rhizosphere soil.For all 3 seasons,shoot fresh weight,root fresh weight,shoot dry weight and root dry weight of cucumber for SBIO+SQR9 treatment were higher than the sterilized bio-organic fertilizer treatment(SBIO).Moreover,the difference between SBIO+SQR-9 and SBIO treatments for the 2nd season showed a significant difference.This result demonstrated that the growth promoting effect for SBIO+SQR-9 treatment is more and more obvious with the increasing season of cucumber continuous cropping.3.The application of bio organic fertilizer could affect the soil bacterial and fungal microbial community based on the high throughput sequencing analysis results using MiSeq platform.The result shows that the bio-organic fertilizer reduced the relative abundance of Acidobacteria,Actinobacteria,Proteobacteria,Basidiomycota,Chytridiomycota,Cercozoa,Glomeromycota and Zygomycota while increased the relative abundance of Bacteroidetes,Gemmatimonadetes,Planctomycetes,Verrucomicrobia,Rozellomycota and Ascomycota at phylum level.Microbial Bio-organic fertilizer application treatment(BIO)significantly improved the Chao richness,and reduced the Shannon diversity for fungal community compared to common organic fertilizer application treatment(OF)and chemical fertilizer application control(CF).At the genus level,the relative abundance of Devosia,Opitutus,Planctomyces,Solirubrobacter and Acremonium was significantly(p<0.05)higher while that of Gemmata,Halomonas,Rhodanobacter,Streptomyces,Arthrographis,Aspergillus,Chaetomium,Geosmithia and Fusarium was significantly(p<0.05)lower for BIO treatment compared to OF and CF treatments Furthermore,Spearman rank correlation showed that the relative abundance of Apodospora and Petriella showed a significantly(p<0.05)positive correlation while that of Devosia,Geodermatophilus,Kaistobacter,Rhodanobacter and Fusarium showed a significantly(p<0.05)negative correlation to cucumber yield.The redundant analysis(RDA)based on microbial community and soil chemical properties illustrated that the first and second axes could totally explained 68.96%and 75.03%variation of bacterial and fungal community,respectively.The organic fertilizer treatments firstly separated from CF treatment according to RDA 1 axes while BIO treatment separated from OF treatment according to RDA2 axes for both bacteria and fungi.Above result indicated that bio-organic fertilizer application could obviously manipulate soil microbial community.In summary,the bio-organic fertilizer application could effectively inhibit the occurrence of Fusarium wilt,and the alter soil microbial community structure and soil physicochemical properties,which manipulated the soil to healthy condition by increasing of beneficial microbes and reducing pathogenic microorganisms.