Influence Of Pipe Drainage On Water And Salt Distribution In Drip Irrigation Farmland

Object:Soil salinization is one of the major obstacles to the development of Xinjiang's agriculture.In recent years,it has relied on reasonable agricultural water-saving technologies and management concepts to transform the cultivated land,and the groundwater level has been reduced year by year.However,the rapid development of oasis agriculture has led to heavy irrigation thought of.In essence,salinity does not break away from the soil,and there is a risk of secondary salinization in cultivated land.Farmland drainage technology has a long way to go.Practice has proved that the long-term application of underground pipe drainage technology plays an important role in the improvement of saline-alkali land and promoting agricultural income.Therefore,the effects of drip drainage on soil water and salt distribution and soil desalination under drip irrigation were studied.The optimum layout parameters of the underground pipe based on the soil desalination effect were deduced,combined with the drainage of the underground pipe during drip irrigation,and the salt salinity elution curve was established.The growth status of the crop under the optimum layout of the underground pipe was sought.Methods:Through field drainage test,drip irrigation method was used to design the depth of buried pipe:0.6 m,1.0 m,1.4 m;pipe diameter:90mm,50mm;spacing:10 m,15 m,20 m,25 m,a total of 3 kinds of dark Pipe layout parameters,unpatched areas,open drainage drainage as a control treatment.Monitoring the distribution of soil salinity and the effect of desalination under the improvement of drainage pipe drainage;Monitoring the discharge,displacement,displacement,salt displacement and dynamic changes of groundwater during drip irrigation.Results:1.The soil moisture content of buried pipe with different depths shows a trend of CK<1.4 m<1.0m<0.6 m overall.The difference in soil desalination rate after drip irrigation was greatest when the pipe diameter was 90 mm and depth was 0.6 m.The salt content in 0~60 cm soil layer was reduced to a slight salinization level(3~6 g/kg).It is suitable for the optimal buried depth and diameter setting parameters of the dark pipe drainage in the northern saline soil.This is of great significance for improving soil salinization.In the future,shallow buried pipes should be used in the design of buried pipes to study changes in salt profiles and shallow groundwater levels during the interannual period of the soil profile.The purpose of improving soil salinity.2.After two irrigations,the total salt content in soil layers above 60 cm is below 10 g/kg,and the soil salt content below 60 cm does not change significantly.The soil desalination rate at 15 m>20 m>25 m>CK is in the range of 51.82%to 60.43%,and the cost per acre is slightly higher at 15m.3.On the basis of drip irrigation and leaching,the flow of the communities in the early stage of drainage increased explosively,and then reached a relatively stable state,and then gradually decreased.The flow rate at the 15 m interval of drainage stage was the largest,reaching 2 m~3/h.During the drainage period,the salinity is at a high level,reaching a maximum of 189.15 g/L.According to the experimental data,the fitting equations under each soil layer can be obtained.In addition to the surface soil,with the increase of soil depth,the equation slope,determination coefficient,and Pearson correlation coefficient are gradually reduced,presenting 20-40 cm>40.The trend of 60 cm>0~20 cm>60~100 cm>100~140 cm>140~200 cm.For every 5 cm increase in groundwater level,the soil salt content in 20-40 cm soil layer has the greatest effect,and the soil salt content will increase 0.89 g/kg,and the impact on 140-200 cm soil is the smallest.4.After three drip irrigation leachings,the total drainage in the test area was 2029.4 m~3,and the salt discharge was 280.1 t;the total drainage volume and salt discharge volume of the ditch of 0,15,20,and 25m were 365.3,671.6,513.7,and 478.8 m~3 respectively.66.4,102.2,59.2,52.3 t;the CK2 of the open channel has lower salt discharge intensity,and the actual desalination effect is not obvious.The distance between the tubes can be well fitted with the elution curve equation.Conclusion:After a long-term irrigation and drainage test,it is concluded that a single open drainage has little effect on improving the original wasteland saline soil in Xinjiang;the soil drainage effect is best when the 15 m-pitch underground drainage system is used.The average drainage rate is 2.87 m~3/h.The salt discharge intensity was 150.3 t/hm~2,and the survival rate of cotton could be more than 60%.The initial 15m spacing was considered suitable as the layout parameter for the drainage distance of saline-alkaline soil in inland arid areas.