| Object: As a sustainable and cost-effective biological inoculant,rhizosphere growth-promoting bacteria(PGPR)can effectively improve soil quality and crop yield.Drip irrigation PGPR,as a new application method,can apply microbial fertilizer,the water and nutrients required by crops to the root zone of crops.It also has the advantages of high efficiency,energy saving,stable improvement effect,strong durability and great potential.In this thesis,we clear the soil microbial mechanism of the drip PGPR and screen the PGPR of saline-alkali land and jujube production by studying the effect of PGPR on saline-alkali soil improvement,physiological growth,yield,quality and soil microbial community of Jujube jujube.This thesis aims to provide theoretical basis and technical support for improving saline-alkali land productivity.Methods: This study collected domestic and foreign literature published from 1990 to 2021.Based on Meta analysis method,we quantitatively analyzed the effects of PGPR on soil improvement and plant yield and quality under salt stress from three aspects: different soil salinity,inoculation methods and PGPR genus.The results of meta-analysis selected nine PGPR which were mainly Bacillus and Pseudomonas(Bacillus subtilis,Pseudomonas fluorescens,Bacillus thuringiensis,Bacillus laterosporus,Bacillus megaterium,Bacillus coagulans,Bacillus licheniformis,Bacillus cereus,Bacillus mucilaginosus)and the control group.From 2020 to 2021,a 2-year planting experiment of jujube in saline-alkali land was carried out.PGPR was applied to jujube in saline-alkali land by drip irrigation system.There were 10 treatments in total and 6replicates for each treatment.The effects of PGPR on saline-alkali soil improvement and physiological growth,yield,quality and soil microbial community of Jujube were studied,and the yield and quality of jujube were comprehensively evaluated by factor analysis.Results:(1)The results of meta-analysis showed that PGPR inoculation could effectively reduce soil salinity,improve soil fertility,increase plant chlorophyll,yield and quality,and increase the content of antioxidant enzymes.Compared with the medium and low saline-alkali conditions,the application of PGPR under severe saline-alkali conditions had a better effect on reducing soil p H and EC and improving crop yield and quality.Inoculation of bacillus had the most obvious effect on the yield and quality of crops in saline-alkali land,and soil inoculation had more advantages than seed inoculation.(2)PGPR improved photosynthesis,increased antioxidant enzyme content,enhanced stress resistance,and improved yield and quality of jujube.Compared with CK group,Bacillus cereus had the most obvious effect on antioxidant enzymes of jujube trees and the contents of catalase(CAT),superoxide dismutase(SOD)and peroxidase(POD)in jujube tree were significantly increased by 15.4%,12.5% and 16.4%.All PGPR treatments could increase the yield and fruit weight of jujube fruit,among which,Bacillus laterosporus,Bacillus coagulans and Bacillus cereus had the most obvious increase on the yield of jujube tree,which increased 25.9%,22.3%,28.9% compared with CK group.In terms of promoting effect of PGPR treatment on the quality of jujube,Bacillus laterosporus,Bacillus coagulans,Bacillus licheniformis,Bacillus cereus and Bacillus mucilaginosus were more advantageous.Factor analysis was used to evaluate the yield and quality of jujube.The optimal PGPR was Bacillus mucilaginosus,Bacillus coagulans and Bacillus laterosporus.(3)PGPR effectively reduced soil p H and EC,and Bacillus subtilis and Bacillus laterosporus were more dominant.Different PGPR had different effects on soil fertility(available P,available K,available N and organic matter),and Bacillus laterosporus significantly promoted available P,available K,available N and organic matter.Bacillus coagulans significantly promoted available nitrogen and organic matter.Drip irrigation PGPR changed the composition and diversity of soil microbial community,and the Shannon index of Bacillus laterosporus and Bacillus coagulans under drip irrigation significantly increased by 9.3%and 8.2% compared with control group.The microbial community composition of Bacillus mucilaginosus and Bacillus coagulans treatment was significantly different from control group.Conclusion: Drip irrigation PGPR could improve photosynthesis,increase antioxidant enzyme content,enhance stress resistance,improve yield and quality of jujube trees,effectively reduce soil p H and EC,and improve soil fertility.Considering the yield and quality of jujube and the improvement effect of saline-alkali soil,the suitable PGPR species for drip irrigation of jujube in saline-alkali land were Bacillus laterosporus,Bacillus coagulans and Bacillus lateralis. |
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