Improvement Effect Of Film Mulching And Organic Fertilizer On Saline Paddy Soil

As an important land resource,saline-alkali land has great development and utilization value.The improvement and utilization of saline-alkali land resources can alleviate the contradiction between man and land,which is of great significance for maintaining sustainable agricultural development and improving ecological environment.The west of Songnen Plain is one of the five major distribution areas of saline-alkali land in China,and also the largest concentrated distribution area of soda saline-alkali land.The saline paddy soil in Songnen plain was improved on the premise of soil improvement.It brought a new research idea for the improvement of saline paddy soil in Songnen plain.The experiment started in May 2021.Two-factor completely randomized design was adopted,and different organic fertilizer measures and different film coating treatments were set as two different factors.Five treatments were set:no applied material（CK）,total rice straw return to the field（SR）,decomposed chicken manure（C）,decomposed pig manure（P）,and biochar（B）.Three levels of no film coating（N）,black film coating（M）and white film coating（W）were set,and a total of 15 treatments were performed.The improvement effect of film mulching and organic fertilizer on saline paddy soil was studied.The results were as follows:（1）Mulching and organic fertilizer can improve the basic physical and chemical properties of saline paddy soil to varying degrees.Among different organic fertilizer measures,treatment B has the best effect on reducing the p H value and EC value of saline paddy soil.Except for total phosphorus,C treatment had the best effect on soil nutrient enhancement.B treatment can increase the field moisture content of soil,make the saturated bulk density of saline paddy soil closer to the optimal value and make the settlement coefficient of saline paddy soil closer to 1.The effect of white film coating is the best.（2）Under different organic fertilization measures,all treatments increased the content of soil total organic carbon and its components,and also improved the carbon pool management index.In addition to water-soluble organic carbon,the content of soil organic carbon and its components in treatment B was significantly higher than that in other treatments,followed by treatment C.At the same time,each treatment can effectively increase the humic acid carbon,fulvic acid carbon,humin carbon,and enhance soil humification degree.Mulching film can also increase the content of organic carbon and its components in saline paddy soil to varying degrees,but the results of this study also showed that mulching film can correspondingly reduce the soil carbon pool management index,indicating that mulching film is not suitable for the accumulation of active organic carbon in saline paddy soil.（3）Different organic fertilization measures could significantly increase the organic carbon content of aggregates of each grain size,which was more significant at the grain size of0.25-0.053mm.At the same time,the content of organic carbon in aggregates increased with different degrees of mulching measures,which was consistent with the law of total organic carbon in soil.The input of exogenous organic materials can increase the proportion of large aggregates in the saline paddy soil,increase the content of MWD,GMD and organic carbon in the water-stable aggregates,and the best treatment is B,followed by C.ELT and D of water-stable aggregates in saline paddy soil were decreased by different organic fertilization measures,and the formation of water-stable large aggregates was also promoted by film coating.（4）In this study,IPP software was used to quantitatively describe the morphological characteristics of aggregates in saline paddy soil.The results showed that the average area,equal circle diameter,eccentricity and roundness of aggregates could be increased by coating and organic fertilizer,while the circumference of aggregates and fractal dimension of aggregate contour could be reduced.Through correlation analysis,it is found that the characteristic parameters of aggregates,their organic carbon and morphological characteristics of aggregates are positively correlated,and negatively correlated with the number of<0.053mm powder clay aggregates,E_LT,aggregate area and contour fractal dimension,indicating that there is a certain correlation between the composition and characteristic parameters of aggregates.The results showed that the composite membrane and organic fertilizer improved the composition of aggregates and the morphological characteristics of aggregates.（5）Using Image J software and Avizo software to analyze the two-dimensional parameters of pore structure of each treatment,the results showed that different organic fertilizer measures could improve the pore structure,pore volume,porosity and fractal dimension of saline paddy soil.The roundness of the saline paddy soil is closer to 1,and the flatness and overall contour coefficient of the saline paddy soil are reduced.With the exception of SR treatment,the pore flatness of saline paddy soil decreased to different degrees with the organic fertilizer treatment,which may be due to the incomplete decomposition of straw in the soil column treated by SR.Treatment B has the largest range in reducing pore flatness and overall contour coefficient of saline paddy soil,while treatment C has the largest range and the best effect in improving pore volume,porosity and roundness of saline paddy soil.The effect of film coating on the pore parameters of saline paddy soil is better than that of non-film coating,and the effect of white film coating is better than that of black film coating.In general,mulching and organic fertilizer were beneficial to the carbon retention capacity of saline paddy soil,increasing the content of organic carbon and its components,promoting the accumulation and renewal of soil humus,and promoting the production and accumulation of new humus.Improve the composition and morphology of soil aggregates,improve soil pore structure.In this paper,the improvement effect of film coating and organic fertilizer on saline paddy soil was studied in order to provide theoretical basis and data support for the treatment of soda saline paddy soil.