Study On Irrigation And Drainage System Of Saline Alkali Land In Songnen Plain

The Songnen Plain is one of the three concentrated distribution areas of soda saline soil in the world and one of the main grain producing areas in China.Soil salinization has always been an important threat to the sustainable development of agriculture in the Songnen Plain.In order to study the suitable irrigation and drainage systems for different types of saline-alkali land in the Songnen Plain,this paper takes the Yueliangpao Irrigation Area as a typical example,and formulates scheme A with one raking and three irrigations and drainage,and scheme B with two rakings and four irrigations and drainage.Two kinds of irrigation and drainage schemes were carried out on the heavy,medium and light saline-alkali land respectively..Based on the comparative analysis,a more reasonable irrigation and drainage system in saline-alkali land soaking period was formulated,and the rationality of the irrigation and drainage system was verified through field experiments in saline-alkali land soaking period.Then,taking the mildly salinized soil in Yueliangbu Irrigation Area as a reference,a field experiment was carried out during the growing period.Through the analysis of the original irrigation and drainage system,and based on the water balance equation and the theory of water-salt migration,the original slightly saline-alkali soil was optimized.According to the irrigation and drainage system in the period,the water demand for field salt drainage of different types of saline-alkali land was calculated by analogy,and the irrigation and drainage system suitable for the heavy,medium and light saline-alkali land in the growing period was calculated.The purpose is to provide theoretical and practical guidance for the saline-alkali and salt leaching and agricultural sustainable development in Songnen Plain.The research conclusions are as follows:(1)The laboratory test results of the irrigation and drainage system in the soaking period of the saline-alkali land show that: Scheme B(4 times of irrigation and drainage and 2 times of raking)has a better desalination effect,and the desalination rates for the heavy,medium and light saline-alkali land are 48.68%,38.65,and 30.66%.Scheme A(3 times of irrigation and drainage,1 time of raking)is relatively more water-saving,and can save water by14.29%.(2)By comparing the salt washing effects of each irrigation and drainage of the two schemes A and B,the comprehensive analysis shows that the relatively reasonable irrigation and drainage systems for different types of saline-alkali soil during the soaking period are as follows: severely saline-alkali soil can be reduced to medium and light saline-alkali land by washing the soil three times.Turn the ground first,do not rake the soil after the first irrigation,shallowly rake the soil after the second irrigation,and deeply rake the soil after the third irrigation.The soil desalination rate About 40%;the moderately saline-alkali soil needs to be washed twice in the field.First,turn the ground,do not rake the soil after the first irrigation,and deeply rake the land after the second irrigation.The soil desalination rate is about 30%;in light saline-alkali fields,the soil is washed once or not.The ground is turned first,and the soil is deeply raked after irrigation,and the soil desalination rate is about 20%.(3)The field experiment of the saline-alkali land during the soaking period shows that the desalination rate can reach 45.29% on the heavy saline-alkali land after soaking three times;the desalination rate can reach 43.43% on the moderately saline-alkali land after soaking twice;the desalination efficiency reached 38.63% after soaking the field in mildly saline-alkali soil once,and the desalination effect was excellent.Compared with the indoor experiment,the heavy saline-alkali land saves 16% of water,and the medium and light saline-alkali lands save more than 50% of water.The irrigation and drainage system has a certain rationality.(4)The results of the field test in the saline-alkali land during the growing period show that the water inflow and the water consumption in the growing period are balanced,and the irrigation and drainage system in the growing period is calculated reasonably.The soil salt content of the test field before soaking in the second year was 34.01 mg/kg lower than that before soaking in the first year,and the desalination rate was less than 2%.The effect of salt washing in the growing period was not obvious.The horizontal salt discharge accounted for12.22% and the vertical salt discharge accounted for 87.78% of the field experiment in the growing period,indicating that the vertical salt leaching played a major role in the growing period.According to the characteristics of crop growth and actual production needs,the final irrigation quota for the heavy saline-alkali land is 1018 mm,991mm for medium,and 963 mm for light.In the same area,the difference in irrigation quotas of soils with different salinity levels during the growing period is mainly reflected in the water demand for field salt discharge.