Response Of Soil Water,Salt And Sunflower Growth To Subsurface Drainage And Simulation Of Field Drainage

Evaporation intensity,poor drainage and high groundwater level are the main factors causing serious soil secondary salinization in Hetao irrigated area,which greatly affect the health of soil and water environment and the sustainable development of agriculture.Based on the field drainage experiment of subsurface pipe drainage,this paper sets up two kinds of buried depth spacing combinations,which are 1.2 m spacing 30 m(T1)and 0.8 m spacing 20 m(T2),to study the distribution of soil water and salt,soil desalination effect,groundwater dynamic changes and the growth status of the sunflower under different subsurface pipe layout parameters.Based on the DRAINMOD model,it simulates the influence of different buried pipe parameters on groundwater depth and optimizes the buried pipe parameters of the last-stage drainage in the field,it aims to provide a certain theoretical basis for the rational implementation and promotion of subsurface pipes drainage to improve saline-alkali land in irrigation areas.The main research results obtained are as follows:(1)The soil moisture and salinity of the soil layer of 0-20 cm have the largest variation range,and the soil moisture and salt of 60-100 cm are relatively stable.The soil mass moisture content of the 0-100 cm profile in different periods of each treatment gradually increased with the increase of soil depth,ranging from 13% to 36%.On the whole,the average soil moisture content of the blank control area is higher than that of the subsurface drainage area.Subsurface pipe drainage facilities can increase the soil desalination rate,and the buried depth of the subsurface pipe is 80 cm and the spacing of20 m is higher than that of the buried depth of 120 cm and the spacing is 30 m.The average soil desalination rate of the buried pipe drainage area for each treatment in the two years was 10.62%,13.20%,8.29%,10.39%,and the control area was 1.25% and-0.07%.The subsurface pipe drainage area can better regulate the soil water and salt conditions than the blank control area,and the treatment of the buried depth of 80 cm and the spacing of 20 m is better than the treatment of the buried depth of 120 cm and the spacing is 30 m.(2)During the sunflower growth period,the buried depth of groundwater in the subsurface drainage area was between 1.56 m and 1.76 m and 1.65 m and 1.85 m,and the control area was between 1.52 m and 1.79 m.There is a positive correlation between the total salt change value of the different soil layers in the subsurface pipe drainage area and the change value of the groundwater depth.In 2019,the salinity of groundwater of the subsurface pipes with the buried depth of 120 cm and the spacing is 30 m and the buried depth of 80 cm and the spacing of 20 m decreased by 7.41% and 10% compared with that in the budding stage,while the groundwater mineralization of the blank control area decreased by 3.13% from 1.92 g/L to 1.86 g/L.In 2020,the salinity of groundwater after harvest for each treatment in the subsurface drainage area decreased by 5.2% and 6.9%compared with that before planting,and the blank control area decreased by 2.51%.It can be seen that concealed pipe drainage can control the buried depth of groundwater and reduce the degree of groundwater salinity,and the treatment and control effect of subsurface pipes with a buried depth of 80 cm and the spacing of 20 m is the best.(3)Under the same irrigation technology and irrigation quota,in 2019,the yield of the buried depth of the subsurface pipe is 120 cm and the spacing of 30 m and the buried depth of 80 cm and the spacing is 20 m increased by 9.38% and 16.88%,respectively;In 2020,its will increase by 14.11% and 25.29% respectively.With the buried depth of 80 cm and the spacing of 20 m,the maximum increase was achieved.Subsurface pipe drainage can effectively increase sunflower production and the effect of increasing production is more obvious.(4)The simulation results based on the DRAINMOD model show that the model has good applicability in the study area.Taking the suitable buried depth of groundwater(1.8-2.0 m)as the basis for optimizing the layout parameters of the drainage subsurface pipes,the simulation results of this model were used to optimize the suitable burying parameters of the drainage subsurface pipes in the study area.