| Soda saline-alkali soil is a serious soil degradation type,and it is also an important reserve cultivated land resource in China.Its soil has poor physical and chemical properties,high p H,high soda content,high exchangeable sodium content,low permeability and low nutrient availability,which seriously affects the treatment and utilization of saline alkali soil.Therefore,the improvement and treatment of soda saline alkali soil is of great significance to the rational use of land and the protection of ecological environment.In order to improve the physical and chemical properties and soil structure of soda saline-alkali soil,promote the agglomeration process of soil,improve the permeability of soil and accelerate the leaching rate of salt ions,this study takes the saline-alkali soil with different degrees of salinization in Songnen Plain as the research object,through the micro saline water leaching test of indoor filled soil column,and applies the technologies of aggregate physical classification,synchrotron radiation micro CT and high-throughput sequencing,This paper discusses the effects of biochar on the structure,salinization characteristics and biological characteristics of soda saline-alkali soil under the leaching condition of brackish water,in order to reveal the regulation mechanism of biochar on the soil structure of soda saline-alkali soil and provide new ideas for the development and utilization of soda saline-alkali soil.The results of this test are as follows:（1）Biochar treatment significantly reduced the bulk density,p H and EC of soda saline-alkali soil,and significantly increased the soil saturated moisture content,but the soil texture did not change significantly before and after improvement.In the soil with the same degree of salinization,sterilization treatment reduced the improvement effect of biochar on the soil,among which the change of moderate soda saline-alkali soil was the most obvious.The soil bulk density decreased by 25.62%,the saturated water content increased by 40.26%,the p H decreased by 12.13%,and the EC decreased by 27.94%.（2）The addition of biochar in the same type of soil increased the content of soil large aggregates,the stability of aggregates was also significantly improved,and the soil structure was more stable.Among them,moderate soda saline-alkali soil treatment changed the most,the content of water stable aggregates≥0.25 mm was39.96%,MWD and GWD were 0.57 mm and 0.59 mm respectively.At the same time,the effect of microbial activity on soil improvement is more obvious in moderate soda saline-alkali soil.（3）Biochar significantly increased CEC,K+,Ca2+and Mg2+of soda saline-alkali soil,significantly reduced the amount of soil SAR,ESP,Na+and total salt,improved the chemical properties of soda saline-alkali soil and reduced the degree of soil salinization.The content of K+increased by 59.80%～136.78%,the content of Ca2+increased by 8.99%～71.77%,the content of Mg2+increased by 3.39%～178.45%,and the content of Na+decreased by-12.44%～45.35%.（4）Biochar significantly increased the species diversity and uniformity of bacterial and fungal communities in soil,and the improvement effect of moderate soda saline-alkali soil was the most obvious.（5）Biochar significantly changed the soil pore structure,and the total porosity increased significantly,with the highest increase of 438.55%compared with control treatment.The proportion of large porosity also increased significantly.At the same time,the pore shape is more inclined to the slender type,which greatly improves the complexity and connectivity of soil pore structure.In conclusion,the application of biochar improves the soil quality of soda saline-alkali soil,improves the soil structure,optimizes the internal environment of soil,slows down the sodium toxicity in soda saline-alkali soil,and provides theoretical basis and technical guidance for the treatment,improvement and utilization of soda saline-alkali soil. |
