Soil Water Movement And Magnesium Ion Transport In Response To Temperature

Rational fertilizer application is an important aspect to achieve efficient agricultural development and ensure high yield and quality of agricultural products.In order to investigate the influence of ambient temperature and infiltration liquid concentration on the transport process of soil water and magnesium ion,this paper studied the adsorption and transport law of soil magnesium ion under different temperature conditions through indoor unsaturated soil horizontal one-dimensional absorption,vertical one-dimensional infiltration and isothermal adsorption test,numerical simulation and theoretical analysis combined to further analyze the transport process of magnesium ion in unsaturated soil,in order to provide scientific basis for agricultural production The main research results are as follows:(1)According to the horizontal one-dimensional absorption test results show that:with the increase of ambient temperature and infiltration liquid concentration,the infiltration rate of soil water accelerates;the relationship between the accumulated infiltration volume and infiltration time is in accordance with Kostiakov model and Philip model;the transport distance of wetting front grows with time as a power function;the horizontal diffusion rate of soil water grows exponentially with the volumetric water content of soil.In the infiltration test with the same volumetric water content,the horizontal diffusivity of moisture is positively correlated with the ambient temperature and infiltrate concentration,and the finer the soil texture is,the smaller the horizontal diffusivity of soil moisture is.(2)In the vertical one-dimensional infiltration test,the infiltration time of chalky loam was about 5 times longer than that of sandy loam,and the magnesium ion content was about twice as much as that of sandy loam.The higher the ambient temperature and the higher the concentration of infiltration solution,the greater the transport distance of soil wetting fronts and the greater the cumulative infiltration volume and water infiltration rate.The relationships between ambient temperature and wetting front,ambient temperature and cumulative infiltration,infiltrate concentration and wetting front,and infiltrate concentration and cumulative infiltration were quantified based on the measured data,and the fitted coefficient of determination R2 was above 0.90;the soil magnesium ion content was relatively high at 20℃,and the magnesium ion content increased gradually with the increase of infiltrate concentration.(3)Through the soil magnesium ion isothermal adsorption test,it shows that the adsorption of magnesium ion of both texture soils increases with the increase of equilibrium liquid concentration,and the adsorption of magnesium ion of chalky sandy loam is larger than that of sandy loam;and with the increase of temperature,the adsorption of magnesium ion of sandy loam and chalky sandy loam gradually increases;the Frendlich equation has the best fitting effect on the isothermal adsorption curve of soil magnesium ion.(4)Hydrus-1D software was used to simulate the process of soil moisture and magnesium ion transport,comparing the measured and simulated values of moisture front transport distance,the fitted coefficient of determination R2 was between 0.96-0.99,the root mean square error RMSE was between 1.03-2.35,the mean difference ME was between 0.70-1.65,indicating that the constructed moisture front transport model was better;comparing The measured and simulated values of Mg ion content in the soil at the end of infiltration,the fitted coefficient of determination R2 was above 0.80,the root mean square error RMSE was between 2.50-6.90,and the mean difference ME was between 1.00-6.20,which was within the allowed error range,indicating that the model can simulate the transport pattern of Mg ion in the soil better.