掺沙对盐渍土土块崩解和土壤盐分淋洗的影响机理

Influence Mechanism of Sand Mixing on Soil Clod Disintegration and Soil Salt Leaching of Saline Soil

黄河三角洲地区的土壤入渗性能差,且盐分含量高,掺沙可以加速盐渍土块崩解,改良土壤质地与结构,从而改善入渗性能和水盐在土壤运移过程。以黄河三角洲地区盐渍土土块为研究对象,采用室内土柱模拟试验,设置3种掺沙比例:CK(0)、S1(20%)、S2(50%),土块组成:<1 mm(20%),1~2 mm(28%),2~5 mm(34%),5~10 mm(18%)研究积水入渗条件下掺沙比例对相继2次入渗过程中盐渍土土块崩解及其对水盐运移的影响,从而明确掺沙对盐渍土的改良效果。结果表明,在第1次灌水淋洗和水分再分布后,用干筛法和湿筛法测量得到S1和S2土壤>0.25 mm的土块含量,较对照组分别降低17.92%,15.50%和51.45%,32.00%;不同掺沙比例下,同一时刻的湿润锋和累计入渗量均表现为S2>S1>CK,且S1和S2的稳定入渗率在第1次和第2次入渗过程中,较对照组分别增加60.00%,66.67%和400.00%,900.00%;同一土层深度的脱盐率随掺沙比例增加,掺沙比例为50%时,脱盐深度比20%和对照组分别增加33.3%和45.45%,脱盐量分别提高1.19%~19.01%和4.21%~77.52%。综上,盐渍土掺沙可以有效促进盐渍土块崩解,提高入渗速率和洗盐效率。研究结果可为盐碱地改良提供参考依据。

The soil in the Yellow River Delta is featured with poor infiltration and high salinity.Sand incorporation into saline soil can promote disintegration of saline soil clods and improve the soil texture and structure,so as to improve soil infiltration and soil water and salt movement in the soil profile.This study used the saline soil clod in the Yellow River Delta as the experimental materials to investigate the effect mechanism of sand incorporation into saline soil on soil clod disintegration and soil salt leaching under three sand incorporation rates:CK(0),S1(20%sands),S2(50%sands),with soil clod composition<1 mm(20%),1~2 mm(28%),2~5 mm(34%),and 5~10 mm(18%).The effects of sand incorporation rates on the disintegration of saline soil and its effect on water and salt transports during two consecutive infiltrations were studied.The contents of>0.25 mm soil clods in S1 and S2 soils were obtained by dry and wet sieving methods.The results indicated that the contents decreased by 17.92%,15.50%and 51.45%,32.00%,in S1 and S2 soils respectively,compared with the control group.Under different sand incorporation rates,the wetting front and cumulative infiltration were in the order of S2>S1>CK.And the stable infiltration rates of S1 and S2 during the first and second infiltration processes increased by 60.00%,66.67%and 400.00%,900.00%,respectively,compared with the control group.The salt leaching rate of the same soil depth increased with the sand incorporation rates.When the sand incorporation rate was 50%,the leaching depth increased by 33.3%and 45.45%compared with 20%incorporation rate and the control group,respectively.The salt leaching amount increased by 1.19%~19.01%and 4.21%~77.52%.In a word,saline soil mixed with sand can effectively promote the salt leaching of saline soil to improve the infiltration rate and salt leaching efficiency.This study can provide a reference basis for saline-alkali soil improvement.