| Under the unique structure of staggered distribution of farmland and wasteland in Hetao Irrigation Area of Inner Mongolia,the problem of soil salinization is developing towards a benign direction,which benefits from previous studies on soil improvement and water-salt migration of cultivated wasteland in Hetao Irrigation Area,enriches and improves the theory of salinization and water-saving irrigation,and provides scientific guidance for local agricultural planting structure and irrigation water quantity.This paper takes farmland and wasteland in Hetao Irrigation Area as the research area,fully combines in-situ test,laboratory test,data analysis and model simulation,aiming at exploring the law of water and salt migration in farmland under the condition of"dry salt drainage",and reveals the quantitative relationship of water and salt migration between farmland and wasteland through the output of water and salt equilibrium equation and model.The main research contents and results are as follows:1.Combining in-situ test with laboratory test,the water-salt balance equation is established according to the actual situation through the data of groundwater level,soil EC,soil water content,meteorology,plant biological characteristics,considering the influence of rainfall,evapotranspiration,groundwater,irrigation water and other factors.Soil salt balance equation was established by referring to soil water balance equation.The spatial variability of soil salinity is strong,and irrigation has a greater impact on it.In the four farmlands,the salinity of soil column per unit area decreased significantly after irrigation,while that of barren land increased.In 2017,irrigation water brought in 72.5 g/m~2 of salt,and irrigation water took away 156 g/m~2 of salt.In the course of irrigation,the salt accumulated in wasteland was 671g/m~2.During the whole crop growth period in 2017(July 1-September 15),the total amount of salt accumulated in soil layer of North Sunflower Land reached 158.3 g/m~2,and that in wasteland reached934.58g/m~2.In 2018,the total amount of salt accumulated in soil layer of North Sunflower Land reached 86.9 g/m~2,and that in wasteland reached 914.4g/m~2.During the growth period,irrigation promoted salt migration between cultivated land,and strong evaporation of soil surface promoted salt accumulation on the surface.2.The HYDRUS-2D model gives better simulation results on the quantitative relationship between water and salt transport between farmland and wasteland.For soil water content,the fitting curve is consistent with the actual situation,and the water content curve fluctuates with the change of groundwater level and rainfall during the simulation period.The longitudinal section a-b is set up.The data of section shows that the salt inflow into wasteland through section A-B is 394 g/m~2 and 332 g/m~2 in the whole simulation period(July 1-September 15).The salt inflow from sunflower to wasteland calculated from measured data is 356 g/m~2 and 310 g/m~2.This is different from the amount of 934 g/m~2(2017)and 914 g/m~2(2018)accumulated by irrigation.There are three reasons:(1)the EC value of groundwater in wasteland is higher,and evaporation of soil surface drives more salt into unsaturated zone of soil;(2)the amount of salt in one direction of wasteland is only considered in this paper;(3)the salt content of wasteland itself is higher,and the spatial difference is large,so it can be calculated.There is a certain degree of inaccuracy.Through theoretical calculation and HYDRUS-2D simulation,the amount of water and salt migration between farmland and wasteland during crop growth period is obtained.The conclusion of this study is a supplement and improvement of the theoretical system of water and salt migration between farmland and wasteland under the"dry salt drainage"model in Hetao Irrigation Area. |
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