Different Irrigation And Arranging Modes, The Distribution Of Water And Salt Nutrient Distribution And Simulation Analysis Of Salt And Salt In The Farmland

The area of salinized arable land in Hetao irrigation area is about 3.94×10⁵ha,which has become a typical salinization irrigation area in China,and improving the salinization degree of land has become one of the urgent problems to be solved.In recent years,large-scale soil improvement and water-saving transformation through drip irrigation have been carried out in saline-alkali areas,but the research on soil water and salt migration law and salt accumulation characteristics of Yellow River irrigation（furrow irrigation）and dark pipe salt discharge,drip irrigation and conventional salt discharge has not been in-depth,so the research on the transport mechanism and simulation of soluble salt and salt separator in salinized soil under different irrigation and drainage modes in Hetao irrigation area was carried out,mainly for yellow irrigation+dark pipe and drip irrigation+The distribution and transport of salt separators in irrigation-soil-drainage were investigated under the two modes of open ditch.In this paper,the temporal and spatial variation and spatial distribution characteristics of soil water,salt and nitrogen are studied for farmland under different irrigation and drainage modes in the irrigation area of Hetao,the interaction response relationship between soil salt and groundwater is explored,the characteristics of soil salt accumulation are analyzed by using the principle of water-salt equilibrium,and then the soil water and salt migration process is simulated and analyzed by HYDRUS-2D model,which provides a theoretical scientific basis for water saving planning and salinization prevention and control in irrigated areas.The main conclusions are as follows:（1）Under different irrigation and drainage modes,the soil moisture content showed a continuous increase with the increase of soil depth.The salt content of 0-120 cm soil layer under drip irrigation and open ditch drainage mode was lower than that under yellow irrigation and dark pipe drainage mode,and the spatial distribution law was reversed.Soil inorganic nitrogen was mainly concentrated in the top soil under different irrigation and drainage modes,the inorganic nitrogen content in the bottom soil was low and stable,and the content was higher under drip irrigation and open ditch drainage mode.（2）The groundwater level under different modes showed a trend of first increasing and then decreasing,and the groundwater buried depth was 0.9-1.2 m under drip irrigation and open ditch drainage mode,and the groundwater buried depth was in the range of 1.0-1.5 m under yellow irrigation and dark pipe drainage mode.The dynamic change of groundwater quality under drip irrigation and open ditch drainage showed an overall upward trend,and the salinity was between 0.6-1.0 g/L,while the mineralization of groundwater under yellow irrigation and dark pipe drainage mode first increased and then decreased,and the overall trend was upward,and the salinity was between 1.0-3.2g/L.（3）There was an obvious correlation between soil salt and ions and EC values under different irrigation and drainage modes,in addition,soil salt accumulation and groundwater quality under drip irrigation and open ditch drainage mode were negatively correlated,HCO₃^-in soil was positively correlated with groundwater ions,and the remaining ions and groundwater ions were negatively correlated.The overall correlation between soil salt accumulation and groundwater quality under yellow irrigation and dark pipe drainage mode was not obvious,and there was a certain negative correlation between Cl^-,SO₄^2-,Ca²⁺and Mg²⁺.（4）Under different irrigation and drainage modes,the soil was in a desalination state,and the soil salinity was mainly concentrated in the 0-20 cm soil layer,and the salt content in the 40-120 cm soil layer tended to be stable,and the content value was much lower than that of the surface soil.The total salt rejection rate was 13.62%under drip irrigation and open ditch drainage mode,the salt content showed surface desalination,root layer salt accumulation,HCO₃^-was in the accumulation state,and K⁺+Na⁺,Cl^-and SO₄^2-had a great influence on the desalination effect.The total soil desalination rate was28.97%under yellow irrigation and dark pipe drainage mode,and the desalination effect of 40-80 cm soil layer was the best,but Ca²⁺and Mg²⁺accumulated between each soil layer,and K⁺+Na⁺,Cl^-,HCO₃^-and SO₄^2-had a great influence on the desalination effect.（5）HYDRUS-2D software was used to simulate soil water and salt under different irrigation and drainage modes,and the simulation value had a high consistency coefficient with the measured value,which had good practical significance.The soil moisture content showed a downward trend under different irrigation and drainage modes.With the increase of irrigation quota and the decrease of drip irrigation belt spacing,the soil salt content of 0-40 cm soil layer decreased significantly,and the salt accumulation in40-80 cm soil layer increased significantly.With the increase of irrigation volume and the decrease of dark pipe spacing,the amount of soil desalination in the 0-80 cm soil layer increased,and the discharge effect of soil salt was better.In summary,considering the distribution of soil water and salt nutrients in farmland under different irrigation and drainage modes,according to the equilibrium and simulation analysis results,it is believed that the effect of water saving and salt control can be achieved by combining drip irrigation and open furrow for light and moderate salinized soils,and for severely saline-alkali land,it is necessary to use furrow irrigation and dark pipe salt discharge to reduce the degree of soil salinization.