Variation Characteristics Of Water,Fertilizer And Salt And Response To Rice Growth In Paddy Field Drained By Underground Drainage In Hetao Irrigation Area

To explore paddy flood irrigation and drainage effect of combined application of salt,2019-2020 in Inner Mongolia Hetao irrigation district Qiu Lin pasture 120 hm2 dark clouds tube drainage paddy set three salt micro change process of monitoring,to explore the different distance and different horizontal distance buried deep in the salt,and numerical analysis,the main influence factors of extracting salt-leaching made up for the inadequacy of the wild field trials bring;On the basis of microscopic monitoring,regional water,fertilizer and salt macroscopic monitoring was carried out to analyze the regional water,fertilizer and salt change rules,and the monitoring area with no hidden pipe(66.67 hm~2)was set as the control.In addition to monitoring the changes of water,fertilizer and salt,rice growth indexes were also monitored.By means of Drainmod drainage model,this paper calibrates and verifies the variation rules of soil salinity and underground drainage during the growth period,simulates the yield and underground drainage under different hidden pipe layout,and explores better hidden pipe layout parameters,and draws the following main conclusions.(1)The desalination rate at different horizontal distances from the concealed pipe and different buried depths of the concealed pipe showed that when the horizontal distance from the concealed pipe was 0m and the buried depth of the concealed pipe was 1.2m,the difference of soil desalination rate after leaching was the largest,and the highest desalination rate appeared at the yellow ripening stage,with a maximum value of 35.11%.The desalination rate in the surface layer was higher than that in the deep layer.The smaller the horizontal distance and the shallower the buried depth,the faster the soil improvement rate was.Hydraulic factor is the main factor affecting the change of salt content.(2)The regional groundwater level fluctuates between 0.78m and 1.16m,which is greatly affected by rainfall and irrigation.The spatial variability of soil salinity decreases with the increase of depth and soil salinity changes toward homogenization.The salt content in Northeast China is higher than that in other regions,and the salt content decreases from heavy to moderate,with the salt discharge about 213-312t.In mid-season nitrogen content is higher than other phases,available nitrogen content at level of 5,different soil nutrient distribution trend generally consistent,20～40 cm soil nitrogen content is higher,nitrogen distribution above the southwest,northeast distribution at level 5 and6 class level,as the drainage of nutrients in the soil spatial heterogeneity.(3)The plant height,leaf area,tiller number and dry matter accumulation of rice showed the rule of dark tubules>CK,and the yellow leaf rate showed the rule of dark tubules CK.There was a significant positive correlation between rice yield and 1000-grain weight and seed setting rate.The utilization efficiency of irrigation water showed that there was a problem of excessive irrigation in this area,and the irrigation water amount could be reduced by 24%-72.75%on the original basis,so as to avoid the waste of water caused by large area flooding.From May to September in 2019-2020,the total drainage time of hidden pipe drainage is 1351h and 1532h respectively,and the total drainage time of CK drainage is 1040h and 1127h respectively.Combined with the analysis of crop water production efficiency and irrigation water production efficiency,it is considered that the use of hidden pipe drainage mode is conducive to crop yield increase.(4)Drainmod model was used to calibrate and verify the groundwater level,salt changes and underground displacement,and then simulated the crop yield and underground displacement under different hidden pipe layout parameters.It was concluded that the hidden pipe layout parameters which could not only effectively reduce the underground water level in this area but also increase the yield were within 1m buried depth and 25m spacing.This parameter can provide a theoretical basis for the treatment of saline-alkali land in this area.