Screening Of Efficent Functional Microorganisms In Improved Saline-alkali Soil

Saline-alkali land spreads more than 100 countries in the world,and China's saline-alkali land covers more 17 million hectares.Yellow River Delta is the important granary near the Bohai Sea.The undeveloped saline-alkali wasteland reaches 180,000 hectares in this region.Affected by the epidemic virus spread in recent years,resulted the global food crisis further intensified,and saline-alkali land has become the reserve land resource with the most development potential.Compared with physical engineering improvement and chemical method improvement,biological improvement has the characteristics of low engineering cost,green without residue,sustainable,and it had been gradually given attention.In this study,soil samples with different salt concentration were collected respectively,and soil physical and chemical characteristics were analyzed,bacteria was isolated from large soil aggregates,and the characteristic of efficient nitrogen fixation,phosphorus and potassium solution,cellulase production,extracellular polysaccharide were evaluated and the efficient strains were screened.The above work provide the evidence and efficient strains for biological improvement of saline-alkali land in the Yellow River Delta area.The main research contents and conclusions are as follows:(1)Soil aggregate classification and physio-chemical properties analyses of saline-alkali soil samples.Fourteen saline-alkali soil samples were collected from the Yellow River Delta region were graded,and the soil physical and chemical properties and the soil enzyme activity were determined.The results indicated that the content of large soil aggregate negatively correlated with saline contration of the soil.The content of available potassium and phosphorus in the all 14 sampling siteswere extremely poor,the contents of the both mineral less than 30 mg/kg and 3 mg/kg respectively.The salt concentration negatively correlated with the soil enzme activities of amylase,sucrase,urease,catalase,and phosphatase.(2)Bacterial diversity in the soil samples.A total of 199 strains were isolated from ten soil samples,and the phylogenetic trees was constrcted by using the 16 S r RNA gene sequences of all representative strains.All the strains were classified within 17 genera,with three dominant genera including Bacillus(61.73%),Pseudomons(12.76%)and Acinetobacter(10.2%)as the dominant groups.The most widely distributed genus was Bacillus,which distributed at all soil samples,followed by Pseudomons,it distributed at nine soil samples.(3)High efficient strain screening.For the representative strains,the ability of nitrogen fixation,phosphorus solution,potassium,cellulose degradation,indindoacetic acid,protease,lipase and extracellular polysaccharide production were evaluated respectively.The results showed that 18 strains with nitrogen fixation ability,among them 4 strains with the strongest nitrogen fixation capacity and they belong to the genera Arthrobacter?Bacillus?Cellulosimicrobium and Cellulosimicrobium.Eight strains have the inorganic phosphorus capacity,among them Bacillus sp.144 showed strongest inorganic phosphorus capacity(6.11 mg/L).Twenty six strains with organophosphorus solutions,Ensifer sp.134 with highest phosphorus solution capacity(81.26 mg/L).Forteen 14 strains with potassium lysis ability,Cellulosimicrobium sp.95 with highest potassium solution capacity(10.6mg/L);Twenty nine strains with strong cellulose degradation abilities were observed,whith Bacillus sp.194 as highest efficient strains(the enzyme was 22.02 IU).Sixteen strains could produce indindoacetic acid,Aeromonas sp.46 has the strongest ability to produce indindoacetic acid(86.02 ?g/L).Seven strains with protease activity,The highest enzyme activity of 20 U/m L was observed for strain Paenibacillus sp.33.Five strains with lipase-producing activity,and highest enzyme activity of 5.54 U/m L was found for strain Bacillus sp.61.Five strains with siderophoreproduction ability,Bacillus sp.184 produced most siderophore of56.6%.And the highest extracellular polysaccharide production ability was observed for strain Mesorhizobium sp.44,which produced more than 0.34 mg/m L.In this study,soil samples with different salt concentrations were collected from the Yellow River Delta region,the physio-chemical properties of the soil were determined,the relationship between salt concentration and phyisio-chemical properties of the soil were evalated,and the efficient strains with different fuctions were screened.The application of related indigenous high efficiency bacteria will effectively enhance the activity of soil enzymes,promote the formation of large soil aggregates,further inhibit soil capillary formation,promote salt leaching,and provide the theoretical and application foundation for the biological improvement of the saline-alkali land of the Yellow River Delta.