| Saline alkali soil is a kind of soil with bad soil properties.It contains a variety of different salts,and the pH of the soil is high.How to make rational use of saline alkali soil is of great significance to alleviate China's food security.Saline alkali soil is widely distributed all over the world,and China is Songnen saline alkali soil,one of the three largest saline alkali soils in the world.Saline alkali soil seriously restricts the local economy and development all over the world,so the research on saline alkali soil all over the world is also more in-depth.At present,there are many ways to improve saline alkali soil,among which biological improvement method has been paid more and more attention because of its less damage to the environment and low cost.In this study,plants and microorganisms were combined to improve the saline alkali soil of Songnen Plain.Firstly,suitable cluster bacteria were selected from the saline alkali soil of Songnen Plain.The growth promoting ability of bacteria was further identified and analyzed.14 strains of bacteria with growth promoting characteristics were screened from the saline alkali soil of Songnen Plain in Northeast China;Among them,there are 6 strains of Acinetobacter,3 strains of Enterobacter and 5 strains of Pseudomonas.Among the 14 strains of bacteria screened,1 had the ability of dissolving potassium,and the content of available potassium in the culture medium increased by 16.24?36.21 mg L-1 compared with the control 12.86± 0.30 mg L-1;12 strains of bacteria had the ability of dissolving phosphorus.The phosphorus content in the culture medium was 0.8 ± 0.1 mg L-1 in the control group and 59.1?233.2 mg L-1 in the inoculated bacteria.The pH value of the culture medium decreased from 6.86 ± 0.34 to 4.06?5.69.The linear correlation analysis showed that the phosphorus content in the phosphorus dissolving culture medium was negatively correlated with the pH value of the culture medium;Seven strains of bacteria had the ability to produce plant growth hormone indoleacetic acid(IAA).When the concentration of substrate tryptophan(L-Trp)was 500 mg L-1,the ability to produce IAA was 5.57?21.11 mg L-1·OD600;Nine strains of bacteria have the ability to produce iron carrier,and the Su value with the strongest ability is 95%.All 14 strains of bacteria could grow in the medium with pH value of 8 and NaCl concentration of 0.5 mol L-1;Four strains could grow in NaCl concentration of 1.5 mol L-1 medium,and b1421 grew well;Five strains of bacteria can grow in the medium with pH 10 and b2222 is the best.The suitable growth promoting bacteria will be selected as the strains for pot experiment with plants.There were three different treatment groups in the experiment:group a planted Suaeda salsa alone,group B planted Suaeda salsa and applied with growth promoting bacteria solution,and group C applied with growth promoting bacteria solution alone.The treatment time was 60 days.After the treatment,the pH,total salt content,urease activity and alkaline phosphatase activity of the upper and lower soil were measured.It is found that group B can significantly improve the physical and chemical properties of upper soil.Under the three treatment methods,group C can significantly improve the activities of soil urease and alkaline phosphatase,and group B has a stronger effect on the activities of soil urease and alkaline phosphatase than group A.This shows that the combined improvement of group B has changed the original water and salt movement process of saline alkali soil and changed the direction of water and salt movement.This improvement effect is stronger than planting plants alone and applying growth promoting bacterial solution.Therefore,the combined improvement can be used as an effective method to improve saline alkali soil in the future. |
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