Effects Of Very Fine Sand Particles On Main Salt Ions In Coastal Clayey Saline Soil

In order to study the effect of extremely fine sand on the salinity and the main salt ions in the coastal clayey saline soil,this paper uses the huge amount of silted sediment in the Yellow River Delta region as the improvement material to study and improve the coastal clayey saline soil in the Yellow River Delta region.The appropriate amount of sediment for diverting yellow sediments was explored through indoor experiments and field improvement experiments of sand distribution.In the laboratory experiment,the soil column simulation method was used to study the changes of soil salinity,the content of main salt ions in the soil,and the proportion of salt ions in the soil.The main results of this research are as follows:(1)The proportion of extremely fine sand between the sediment from the Yellow River Diversion and the clayey saline soil is quite different.Studies have shown that very fine sand particles can inhibit soil adsorption of salt.After salt water leaching and deionized water leaching,the soil salinity decreased significantly with the increase of the proportion of very fine sand particles.A quantitative equation was established between the fraction of very fine sand and soil salinity after saline and deionized water leaching.(2)Very fine sand particles can inhibit the adsorption capacity of clayey saline soil for Na⁺,K⁺,(Ca²⁺+Mg²⁺).After salt water leaching and deionized water leaching,the Na⁺,K⁺,(Ca²⁺+Mg²⁺)contents of soil decreased with the increase of the proportion of very fine sand particles.The proportion of Na⁺in cations decreased with the increase of the proportion of ultra-fine sand,and the proportion of K⁺in cations increased with the increase of the proportion of ultra-fine sand.Under the condition of salt water leaching,the change trend of the proportion of(Ca²⁺+Mg²⁺)in cations is opposite to that under the leaching condition of deionized water.(3)Very fine sand particles can inhibit the adsorption of Cl^-in clayey saline soil.However,with the increase of the proportion of very fine sand particles,the inhibitory effect weakened.When the proportion of very fine sand particles was 4.42%-12.63%,the proportion of Cl^-to anion after salt water leaching and deionized water leaching was lower than that of the control treatment.It can inhibit the adsorption of SO₄^2-in clayey saline soil.The SO₄^2-content decreased with the increase of the ratio of ultrafine sand particles,but the proportion of SO₄^2-in anions first increased and then decreased.(4)After leaching with salt water,when the proportion of extremely fine sand particles is8.52%,the proportion of total salt in the soil column(Na⁺+Cl^-)is the lowest,which is 50.82%.After leaching with deionized water,when the proportion of very fine sand particles is28.26%,the proportion of total salt in the soil column(Na⁺+Cl^-)is the lowest,which is40.12%.Very fine sand particles can effectively reduce the proportion of(Na⁺+Cl^-)in the total salinity in the soil,and enhance the leaching effect of deionized water on(Na⁺+Cl^-).(5)In field experiments,extremely fine sand particles can effectively reduce the soil salinity of the topsoil and the tillage layer,and the proportion of total salinity(Na⁺+Cl^-)in the topsoil and the tillage layer soil is significantly reduced.In 2020,the proportion of(Na⁺+Cl^-)treated by S3 in the total salinity was the lowest,which was 52.62%in the 0-20cm soil layer and 50.89%in the 20-40cm soil layer.In the 0-20cm soil layer in 2021,the soil treated with S4(Na⁺+Cl^-)accounted for the lowest proportion of total salinity,which was 48.56%.In the20-40cm soil layer,the soil treated with S3(Na⁺+Cl^-)accounted for the lowest proportion of total salinity,which was 47.89%.(6)In field trials,extremely fine sand grains can effectively improve winter wheat yield.In 2020,the wheat yield of S3 treatment was the highest,at 5695.46kg/hm~2.In 2021,the wheat yield of S3 treatment was the highest,at 6643.95kg/hm~2.