Study On Leaching Effect Of Saline-alkali Soil In Shule River Irrigation Area

This article takes the saline-alkali land of the Huanghua settlement in the Shule River Basin of the Hexi Corridor as a research area.In order to explore the effects of water conservancy and chemical improvement methods on the improvement of the saline-alkali soil in the area,based on summarizing research progress and improvement measures of the saline-alkaline soil improvement at home and abroad,the Water leaching and FeSO₄ leaching to improve the saline soil in the area.In order to improve the saline-alkali soil at the Huanghua No.1,Huanghua No.3,and Huanghua No.4 in the Shulehe Irrigation District of Gansu Province,27 soil profiles were taken using the GPS positioning technology.The soil column leaching test was used to study the soil profiles.The permeation rate and the soil permeation rate of each layer?0-30cm,30-60cm,60-100cm?were graded for permeability;the salt content and composition,EC,pH,and available nutrient of the soil before and after leaching were evaluated.A comparative analysis was carried out to test the emergence rate of wheat in the improved soil in order to provide a scientific basis for the improvement and utilization of saline-alkali land in the Huanghua settlement.The main conclusions are as follows:1.Profile Permeation Rates The overall permeation rates of the 27 profiles studied were 1.58mm/h-47.79mm/h,all between slow-medium,with slow,slightly slow,and moderate permeation rates of 40.7%,33.3%and 25.9%;infiltration rate limited soil layer is mainly 60-100cm.2.Effect of leaching on water-soluble salts Leaching reduces the water-soluble salts in all layers of the soil.After 5 times of rinsing,the average water-soluble salt leaching rates of 0-30cm,30-60cm,and 60-100cm were 88.9%,82.7%,and 73.6%,respectively;the higher the salt content,the greater the salt rejection.3.Effect of leaching on the composition of water-soluble salt separators The cation content of 0-30cm and 30-60cm soil layers was Na⁺>Mg²⁺>Ca²⁺>K⁺before leaching,and the cation content of 60-100cm soil layers was Na⁺>Ca²⁺>Mg²⁺>K⁺,the order of the anion content in the three levels is SO₄^2->Cl^->HCO₃^->CO₃^2-.After 5 times of leaching,the order of cation content of 0-30cm soil layer is Na⁺>Mg²⁺>Ca²⁺>K⁺,and the order of cation content of30-60cm soil layer is Na⁺>Ca²⁺>Mg²⁺>K⁺,and the cation of 60-100cm soil layer.The order of the contents is Na⁺>Mg²⁺>Ca²⁺>K⁺,and the order of the anion contents in the three levels does not change.The leaching rates of Na⁺at each level were 87.1%,81.9%,and 73.0%,respectively.4.Effect of leaching on soil ECWater leaching and FeSO₄ leaching 1-3 times significantly reduced the EC of the top soil layer,but after 3 times of leaching,the soil EC decreased minimally.Water leaching and FeSO₄ leaching have similar effects on soil EC reduction.5.Effect of leaching on soil pH Both water leaching and FeSO₄ leaching can reduce the pH of each layer of the soil profile.The higher the pH of the original soil,the more obvious the pH drop is for rinsing.The leaching effect of FeSO₄ is better than that of water leaching.6.Effect of leaching on available soil nutrients Water washing resulted in the loss of alkali-hydrolyzable nitrogen and available phosphorus in soil.After 3 times of water washing,the cumulative leaching rate of soil alkaline leaching nitrogen was 39.3%,and the cumulative leaching loss rate of soil available phosphorus was 11.1%.The leaching losses of alkali-hydrolyzed nitrogen and fast-acting phosphorus were 14.97 mg/kg and 1.87 mg/kg,respectively,and were significantly positively correlated with their original soil contents.Therefore,in the process of saline-alkaline soil improvement,nitrogen fertilizer and phosphate fertilizer should be added to the soil after salt washing.7.Effect of leaching on the emergence rate of wheatThe emergence rate of unleached wheat from saline-alkali soil at No.1,No.3,and No.4 of No.1 was 0%?except for section 11 and section 19?.After three times of water leaching and FeSO₄ leaching,the emergence rate of wheat was greatly increased.The increase was 83.4%and 84.3%,80.6%and 85.1%,82.9%and 89.3%,respectively,indicating that FeSO₄ leaching was higher than that of water-leached wheat by 0.9%,4.5%and 6.8%respectively.8.Salt alkali soil desalinationThe leaching of the Shule River Irrigation District should be carried out in 3 separate leaching steps.Each leaching amount is 4000m³/hm²,and the total leaching amount is 12,000m³/hm².When each leaching is performed,1kg/m³ is added at the outlet.For FeSO₄,the interval between rinses is based on the dryness of the field water.The washed soil can grow crops.