Effect Of Mixing Sand With Surface Soil On Saline-Alkali Soil Water-Salt Transport And Summer Corn Growth

In order to explore the improvement effect of mixing sand with surface layer?0²0cm?on saline-alkali soil in the Yellow River delta region,one-dimension vertical infiltration experiment was conducted in laboratory to study the effects of different types of saline-alkali soil and proportions of sand on soil water infiltration and the distribution of soil water and salt.The test soil contains moderate saline-alkali soil(2.381g·kg^-1)and severe saline-alkali soil(4.099g·kg^-1),and the experiment sets 5 sand-mixing ratios:CK?0%?,S1?5%?,S2?10%?,S3?15%?and S4?20%?.Field sand mixing experiments were carried out in Binzhou area,to study the influence of mixing sand on soil profile moisture content and salt content in field,and to investigate the changes of growth indexes and yield of corn maize with mixing sand.Field experiments were conducted with four treatments:CK?0%?,S1?5%?,S2?10%?and S3?15%?The main research results showed that:?1?At the initial stage of infiltration,the cumulative infiltration and wetting front depth increased rapidly,but gradually slowed down with the increase of infiltration.Cumulative infiltration was in good linear relationship with wetting front depth?R²>0.99?.The cumulative infiltration and the wetting front depth of the severe saline-alkali soil with the same sand-mixing proportion were all greater than those of the moderate saline-alkali soil at the same time,and the infiltration ending time of the severe saline-alkali soil were all less than moderate saline-alkali soil.The two types of saline soil show the same rule s after the surface layer of sand mixing:the surface layer of sand mixing will increase the rate of soil water infiltration.For the same infiltration duration,the larger the proportion of sand mixing is,the larger the cumulative infiltration and wetting front depth will be.At the end of infiltration,mixing sand with surface soil increased the wetting front depth,which is proportional to the proportion of sand.The curve of infiltration rate with time changes from steep to gentle,and gradually tends to a stable infiltration rate,the infiltration rate of each treatment is as follows:S4>S3>S2>S1>CK,compared with Green-ampt model and Philip model,Kostiakov model has the best fitting result,which is more suitable to describe the relationship between infiltration rate and time under the condition of sand-mixing.?2?Mixing sand with surface layer could reduce soil moisture content of surface layer,improving the lower the moisture content of soil,two kinds osaline-alkali soil mixed sand moisture content and decreased with increment of mixed sand proportion,moisture content of the soil without sand changed slightly differently:moderate saline soil surface mixed sand will significantly improve the subsoil moisture content,the mixed sand treatment 15%of the soil moisture content is the highest;The water content of the subsoil is also increase d by the addition of sand to the surface layer of severe saline soil,among which the subsoil with sand content of 20%has the highest water content.The one-dimensional algebraic model was used to fit the profile moisture content distribution of sand mixed soil in the surface layer,the results showed that the fitting accuracy of moderate saline soil is low,the model parameters need to be modified,and the fitting accuracy of severe saline soil is high.?3?0⁴5cm is the soil desalting area,the soil sali nity is obviously less than the initial soil salinity.The soil layer of 45⁶0cm is a salt-accumulation area,and the soil salinity increases rapidly with the increase of depth,which is greater than the initial soil salinity and reaches the maximum value at the humid front.The overall salinity of moderate saline soil is shown as CK>S1>S2>S4>S3,except for S4 treatment,soil salinity decreases with the increase of sand-mixing proportion.The overall salinity of severe saline soil is shown as CK>S1>S2>S3>S4,soil salinity is inversely proportional to the proportion of sand content.The desalinization effect of each treatment was evaluated by using desalinization indexes:Mixing sand with surface layer could improve the efficiency of salt leaching.The best desalinization effect was achieved by mixing sand with surface layer of moderate saline soil at 15%,and the best desalinization effect was achieved by mixing sand with surface layer of severe saline soil at 20%.?4?The data of field experiment for two years showed the same rule:the soil moisture content of sand layer 0²0cm could be reduced by adding sand to the surface layer,and the soil moisture content decreased with the increase of sand proportion.After adding sand to the surface layer,more water entered into the subsoil,which increased the soil moisture content of the soil layer of 20⁶0cm,soil moisture content is proportional to the proportion of sand.The salt content of field soil is reduced by mixing sand with surface layer,the higher the proportion of sand content,the more obvious the reduction of soil salt content.The plant height,stem diameter,leaf area and dry matter weight of summer corn increased in the whole growth period after the surface layer of field soil was mixed with sand,the field treated with sand content of 15%had the best growth.Mixing sand withsurface layer increased the yield of summer corn,the rate of growth of 2017 was between 6.46%¹0.40%and 2018 was between3.72%¹2.55%,the yield of corn is proportional to the proportion of sand.The field experiment results showed that the best ratio of surface moderate saline soil mixed with sand was 15%,which verified the conclusion of the laboratory experiment.