| The coastal saline-alkali soil in the Yellow River Delta is an important reserve land resource and has huge potential for agricultural development.However,due to frequent water and salt movement,the soil has obvious characteristics of "saline,alkaline,harden,and nutrient-poor",and soil phosphorus is often fixed by calcium,resulting in effective Very low sex,difficult to improve.In the soil environment of farmland soil,the external addition of phosphorus solubilizing bacteria can promote the effectiveness of Ca-P and increase the supply of available available phosphorus for plants.However,the types of phosphate-solubilizing microorganisms in saline-alkaline environments are relatively small.There are few reports on its growth and adaptability in saline-alkaline soil.At present,the phosphate-solubilizing bacteria discovered in current research often have poor colonization,low activity,and unstable function due to insufficient salt-alkali adaptability in the application of saline-alkali soil improvement,which have become the bottleneck of the improvement and utilization of saline-alkali soil.In response to the above problems,this study used the marine bacterial strains with a wide range of saline-alkali adaptability possessed by the laboratory to screen a series of saline-alkali-suitable phosphate-solubilizing marine bacteria,and explored the effects of salinity,pH,temperature,carbon source,nitrogen source and adaptability to saline-alkali soil environment of 6 phosphate-solubilizing bacteria with good phosphate-solubilizing effects.And the mechanism of dissolving phosphorus was preliminarily discussed.Using industrial and agricultural waste as a carrier,a strain of Bacillus paramycoides 3-1a with better performance was selected to prepare microbial organic fertilizer.Potted experiments were conducted to explore the effects of applying phosphorus solubilizing bacteria and microbial fertilizer on plant growth and the physical and chemical properties of saline-alkali soils.,Soil enzyme activity and the influence of microbial community.The main research contents and conclusions are as follows:(1)In this study,a batch of phosphate-solubilizing strains were screened from the marine strain resource bank that produced exopolysaccharides,and 6 strains with the best phosphorus solubilizing effect were selected(Pseudomonas palleroniana 4-2,Bacillus paramycoides 3-1a,Bacillus cereus 2-8a,Bacillus thuringiensis 2-7a,Oceanobacillus kimchii 3-6b,Oceanobacillus iheyensis 3-10b)to explore phosphate solubilizing quantity under different salinity,pH,temperature,carbon source and nitrogen source,the survival and environmental behavior in saline soil.The results showed that the 6 strains of bacteria have different adaptability to various environmental factors.Strains 2-7a and 2-8a have good phosphorus solubilization effects in the salinity range of 0-10%and pH 7-10.It has a good phosphorus solubilizing effect in the pH range of 0-8%,pH 7-9,and the above three marine Bacillus have a phosphate solubilizing effect when using a variety of carbon sources and nitrogen sources.The results of soil culture experiments showed that the inoculation of 3-1a can reduce the soil pH by about 0.07,and the content of soil available nitrogen and phosphorus increased by 24.2%and 18.2%respectively compared with the control,indicating that strain 3-1a has a wide range of saline-alkali and nutrient adaptations,and it can survive in saline-alkali soil and play a role in dissolving phosphorus,and has broad application prospects.(2)Spearman correlation analysis shows that the amount of phosphate solubilized by strains is significantly negatively correlated with the pH of the medium.Continuous culture experiments have verified that the phosphate solubilization is caused by the drop in the pH of the medium;liquid chromatography-mass spectrometry(LC-MS)explored the differences in the types of organic acids secreted by the strains with and without tricalcium phosphate stress.The results showed that strain 3-1a produces gluconic acid,citric acid,lactic acid,malic acid,succinic acid,propionic acid,and acetic acid when dissolving phosphorus.7 kinds of organic acids,4-2 5 kinds of organic acids,citric acid,lactic acid,malic acid,and succinic acid are produced when dissolving phosphorus.When there is no calcium phosphate stress,the two strains will not produce malic acid;observed by SEM After dissolving phosphorus,the sharp crystals of tricalcium phosphate became short and smooth,and a large number of micron-sized tricalcium phosphate particles were stained on the surface of the bacteria,which verified the interaction between bacteria and calcium phosphate.(3)Mixed fermentation of edible fungus planting waste,corn cob powder and strain 3-1a by semi-solid fermentation method to prepare microbial organic fertilizer.Through indoor pot experiment,four different treatments of control group(CK),strain 3-1a treatment group(BB),organic fertilizer treatment group(OF),and self-made microbial organic fertilizer treatment group(BOF)were explored on the growth of Chinese cabbage.The influence of soil physical and chemical properties,enzyme activity and microbial community structure.The results showed that BOF treatment effectively promoted the growth of Chinese cabbage.Compared with the control,the soil pH decreased from 8.12 to 7.64,and the content of available nitrogen and phosphorus increased by about 5 times and 30 times compared with the control.Soil urease and alkaline phosphoric acid Enzyme and catalase activities have increased,and soil functional microbial groups have changed,indicating that this program has a good improvement effect on saline-alkaline soil.In summary,in this study,the phosphate-solubilizing marine bacteria with wide saline-alkali adaptation range were screened,and their phosphate-solubilizing mechanism was proved.The microbial organic fertilizer was successfully prepared,which effectively promoted the growth of plants and the improvement of soil fertility,enriched the resources of phosphate-solubilizing bacteria suitable for saline-alkali soil,and had engineering guiding significance for green reclamation of saline-alkali soil... |
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