Influence Of Micro-topography On Soil Salinity In The Process Of Phreatic Water Evaporation

Salinity is the main obstacle to the development and utilization of salinized soil,which severely restricts the sustainable development of regional agriculture and social economy.Therefore,clarifying the causes of salinization and its regularity,and then adopting appropriate prevention and control measures to improve the utilization of salinized soil resources is one of the important measures to increase the reserve resources of arable land and ensure food security.On the basis of comprehensive analysis and reference to the improvement of salinized soil technology and research results at home and abroad,this thesis focuses on the formation of soil salinization and its seasonal changes in the Yellow River Delta,and takes the rational development and utilization of land resources and scientific improvement of saline-alkali land as the main starting point.,And then increase the available cultivated land reserve resources as the main purpose.By constructing a micro-topography(furrow and ridge system)on the salinized soil surface,the salt accumulation surface is raised to remove the salt in the soil profile by using the characteristics of soil salt accumulation on the surface,and the effect of micro-topography on the soil under the condition of phreatic evaporation is emphasized.The influence of salt transport and spatial distribution characteristics and its mechanism of action are expected to seek new ways and provide important theoretical basis for the improvement of salinized soil and the construction of ecological environment.The research has reached the following conclusions:(1)The study of soil water transport performance shows that the cumulative infiltration volume and cumulative infiltration volume of soil water follow the same changing law,and the initial and stable infiltration rates of each soil layer under the conditions of infiltration are higher than those in infiltration.Process:The Philip formula and Kostivkov formula are used to simulate and analyze the infiltration process and the imbibition process.The results show that the Kostivkov two-parameter model can better simulate the dynamic change process of the infiltration rate in the process of saline soil imbibition,and the coefficient of determination is R²Both are above 0.96;the wetting front and cumulative infiltration amount during the infiltration process,and the wetting front and cumulative infiltration amount during the imbibition process all show a significant linear relationship,and the coefficient of determination is greater than 0.99.(2)The results of the study on the accumulation mechanism of soil salt show that at the end of the imbibition,the conductivity,Na⁺,Cl^-of the surface soil solution is higher,but the content of SO₄^2-is lower;as the storage time increases,soil salt ions appear in the soil Redistribution,showing that the surface soil solution conductivity,Na⁺,Cl^-of each treatment are lower than the control(take soil immediately,0d),and the SO₄^2-content is higher than the control;the soil under the surface(2-8cm)of each treatment Solution conductivity,Na⁺,Cl^-ion content increased,and higher than the control,and increased with the increase of the storage time,while the SO₄^2-decreased with the increase of the storage time.This phenomenon indicates that the salt will accumulate in the surface layer at the end of the imbibition.Later,if the evaporation is not very strong,the redistribution of the salt in the profile may occur at the level with relatively high water content.(3)Research on the influence of micro-topography on the spatial distribution of soil water and salt shows that compared with flat cropping(CK),the three ridges all increase the soil moisture content of the surface layer of the furrow,and the moisture content of the arch,triangle and trapezoid increases by 14.07%respectively.,9.69%and 2.79%;from the average surface water content,the water content of the arched ditch is higher than other ridge treatments.The distribution of soil moisture content in different soil layers of each treated ridge section generally shows a trend of gradually increasing from the surface layer to the deep layer;the moisture content of each treated ridge reaches the maximum in the1cm soil layer(close to the center of the ridge and furrow junction),and the trapezoid treatment has a high moisture content.In other treatments,it was 14.97%;the distribution of soil moisture content in different soil layers under the ditch and ridge of each treatment had no obvious regularity.(4)The results of the study on the characteristics of the spatial distribution of salt in the micro-topography soil profile show that in terms of surface soil,compared with flat cropping(CK),Na⁺,Cl^-and SO₄^2-in the surface layer of the ridged soil have increased.After the ridge treatment,the soil surface conductivity,Na⁺,Cl^-basically increased from the furrow on both sides to the ridge.The triangular ridge has a stronger effect on the accumulation of Na⁺and Cl^-on the soil surface.Comparing the soil salinity between ridges and furrows,ridges caused more soil salinity to accumulate on the ridges,which increased the soil electrical conductivity,Na⁺content and Cl^-content of the ridges;from the comparison of the peak SO₄^2-content of each treated ridge with the furrow,the ridged treatment was effective To a certain extent,the SO₄^2-content of the groove is reduced.According to the distribution of salt in the soil profile,compared with flat cropping,the salt concentration on the upper surface of the soil after ridge treatment is obvious,and the soil salt in the ridge is higher than that in the furrow.Under the three types of micro-topography,the salt accumulation effect of the ridge is obvious,and the triangular ridge is more conducive to the accumulation of salt on the soil surface.In summary,the method of constructing micro-topography on the surface can regulate the movement and spatial distribution of soil water and salt,and the effects of different micro-topography forms on water and salt are also quite different.The effect of micro-topography is also closely related to its cross-sectional shape parameters,and this article has not yet involved research in this area.Therefore,future research will be carried out in the field of cross-sectional parameter setting and field test verification.