Microscale Spatial And Temporal Variation Characteristics Of Soil Salt Content In Coastal Salinized Farmlands

Reserve resources of the Yellow River delta is China's important middle-and-lowyielding fields area,agricultural development potential is tremendous,but because of the bohai sea,groundwater buried depth,high salinity and its distribution have a large number of coastal salinization of soil,together with the area of farmland is unreasonable farming and artificial management measures,such as irrigation and drainage,easily lead to the occurrence of secondary salinization problems,It seriously restricts the sustainable development of local ecology and economy and threatens the level of agricultural production.Therefore,it is of great significance to explore the temporal and spatial variation characteristics of salt in coastal saline soil,especially to implement fine monitoring of soil salt in micro-domain scale,for the formulation of soil salt control countermeasures,rational development and improvement and utilization of coastal saline soil in coastal saline farmland.This paper choose typical inshore saline farmland in typical domain as the research object,the micro topography,soil compactness in farmland,the surface coated and the surface vegetation cover more than four kinds of typical micro domain sampling season observation(1 time in the spring,summer,autumn),through the statistical analysis,field observation,variance analysis and comparison of data analysis method,Farmland is studied in the typical micro domain level of time and space variation characteristics of soil salt content,and through the simulation test,carries on the micro topography,soil compactness,the earth's surface and coated and straw four kinds of typical field simulation,analyzed the natural evaporation under the condition of the micro domain dynamic change law of soil salt content,so as to provide reference for micro domain of soil salt regulation.The main research contents and conclusions are as follows:(1)Influence of microtopography on variation of soil salt content.The microtopography of saline farmland showed moderate variability in spring,autumn and summer,with the highest variation coefficient reaching 31.79%.In spring and autumn,when evaporation was the main factor,soil salt accumulated on ridges,and soil salt content was significantly different between ridges and ridges.The risk of salinization was relatively low in ridges and ridges,and the soil salt content in the ridge furrow decreased 46.42% compared with the ridge top.Under the influence of frequent rainfall in summer,the soil salt content in the ridge and low-lying areas was higher than that in the ridge and low-lying areas.The soil salt content inthe ridge and low-lying areas was 31.82%higher than that in the ridge and low-lying areas,but there was no significant difference in individual micro-areas.The results of micro-terrain simulation showed that the soil salt content on the top of ridge slopes increased continuously under the condition of natural evaporation.When simulated rainfall occurred,the soil salt content in the ridge and low-lying areas increased in a short time,and then desalted,and the soil salt accumulated rapidly on the top of ridge slopes.(2)Influence of soil compactness on soil salt content variation.The variation intensity of soil compactness was moderate in spring,autumn and summer,with the highest variation coefficient reaching 31.39%.There were significant differences in soil salt content in different parts of soil compactness in each season,and soil salt content was higher after mechanical compaction than that in good tillage,with a maximum increase of 78.71%.Simulation test of soil compactness shows that salt accumulates faster in the relatively tight soil under natural evaporation,and salt leaching is better in the relatively loose soil after simulated rainfall,but there is a phenomenon of soil salt accumulation after rainfall.(3)Effects of plastic film mulching on variation of soil salt content inside and outside plastic film.In spring and autumn,the variation coefficient of each plastic film covered micro-area was medium,reaching 21.68%.After the summer rainy season,the variation degree was weak,which was weak variability.In each season,the soil salt content in the medium and micro film was lower than that in the outer film,and the soil salt content in the outer film was 46.11% higher than that in the outer film.The soil salt content in the micro film was significantly different in spring and autumn,but the soil salt content in the outer film was not significantly different after the rainy season in summer.The simulation test of surface film mulching showed that the soil salt content outside the film rapidly accumulated to the surface layer under natural evaporation,and the soil salt content inside the film had little change.The effect of salt leaching in film after simulated rainfall is not good,and the soil salt content tends to increase.(4)Effects of weeds and straw mulching on soil salinity variation.In the saline farmland,the variation was slightly stronger in spring and autumn,indicating moderate variation,and slightly weaker in summer after the arrival of rainy season,indicating weak variation,with the highest variation coefficient of 7.01%.There was a significant difference in soil salt content between exposed and overgrown areas.Soil salt content in overgrown areas was lower in each season,and soil salt content in overgrown areas was reduced by 32.59% compared with that in exposed areas.The simulation experiment of straw mulching showed that the straw mulching inhibited the accumulation of soil salt to the surface under the condition of natural evaporation,and the straw mulching continued to inhibit soil salt accumulation after simulated rainfall.In this study,the temporal and spatial variation characteristics of soil salinity in typical microdomains of coastal saline farmland were well explored,which provided theoretical basis for microdomain regulation of soil salinity in saline farmland and efficient crop cultivation and management.