Effects Of Different Improver On Infiltration Characteristics And Distribution Of Water And Salt In Saline-alkali Soil

As a populous country,China is not completely self-sufficient in grain production.The amount of arable land in our country is limited,which can not meet the needs of our economic and social development more and more.Saline-alkali land is an important land resource.Improving the saline-alkali land can effectively expand the arable land area and increase grain output.The ameliorating methods of saline-alkali soil include water conservancy engineering ameliorating measures,physical ameliorating measures,etc.Chemical ameliorating measures can change the composition of soil colloid adsorbent ions,improve soil structure,etc,which is conducive to soil desalination and rehalting,and promote plant growth.In order to study the effects of different dosage,depth and layer location of modifiers on the distribution of water and salt transport in saline-alkali soil,a one-dimensional vertical infiltration test was conducted in the laboratory.In this thesis,six kinds of improved materials,such as organic silicon functional fertilizer,wheat straw,wheat decayed straw,calcium sulfate,Shidijia,Minxin-ke salt and alkali,were selected to analyze the effects of different dosage,depth and layer location of the improver on the infiltration characteristics of saline-alkali soil,infiltration model parameters,and water and salt migration rules.It is expected to provide the basis for the use of ameliorant and the improvement of saline-alkali soil.The main findings are as follows:(1)The effects of different amendments and application rates on soil infiltration characteristics and soil electrical conductivity are revealed.Under the same improer condition,the migration distance of wetting front and the cumulative infiltration amount decreased with the increase of the application amount,which indicated that silicone functional fertilizer,The straw of wheat,wheat decaying straw and calcium sulfate had a certain infiltration reduction effect,while applying dijia and minxin-g salt and alkali could promote the infiltration of soil water to a certain extent.In the case of different modifiers and dosages,the wetting front migration distance and time,velocity and cumulative infiltration amount and time all showed a good power function relationship.Kostiakov and Philip infiltration model fitted the power function relationship of cumulative infiltration amount and time better,and the decisive coefficients were all above 0.97.The application amount of the improver had an effect on the fitting coefficient of different mathematical models.With the increase of the application amount of silicone functional fertilizer,The straw of wheat and wheat decayed straw,the fitting coefficient gradually decreased,and with the increase of the application amount of calcium sulfate,the fitting coefficient first increased and then decreased.Different amendments and application rates have an impact on the distribution of soil water content.The soil moisture content decreases with the depth of the soil layer.The application rate of organic silicon functional fertilizer affects the distribution of soil water content in the depth of the soil layer.At the depth of 0?3cm,the soil water content drops sharply;at the depth of 3?20cm,the soil water content decreases relatively smoothly.The differences are small and all are greater than the control treatment.At the same depth of soil layer,the soil layer containing wheat straw and decomposed straw increased soil water content significantly.With the increase of the mixed application of calcium sulfate in each treatment,the difference in soil water content was not significant.Different improver and application amount affect the change of salt content in soil depth.Under different application rates of silicone functional fertilizer,wheat straw,wheat decayed straw and calcium sulfate,the demarcation line between desalting zone and salt accumulation zone was about 14 cm,10cm,11 cm and 7cm in soil depth,respectively.Improver and dosage affect the conductivity in different soil depths.In the soil depth of 0?10cm,the soil conductivity gradually decreased with the increase of the application amount of silicone functional fertilizer and was lower than that of the control treatment.When the soil depth was more than 10 cm,the soil conductivity gradually increased with the increase of the application amount of silicone functional fertilizer.The accumulation of salt in saline-alkali soil was caused by the wheat straw,and the salt was not easy to infiltrate with water.With the increase of the application amount of the wheat straw,the soil electrical conductivity also increased,which was higher than that of the control treatment.The soil electrical conductivity increased with the increase of wheat decayed straw application amount.In the soil depth of 0?7cm,the soil conductivity gradually decreased with the increase of calcium sulfate application amount;in the soil depth of 7?20cm,the soil conductivity gradually increased with the increase of calcium sulfate application amount.(2)The effects of different amendments and application depths on soil infiltration characteristics and soil electrical conductivity are revealed.Under the same improver,with the increase of applying depth,the migration distance of wetting front and the cumulative infiltration amount decreased.For the same infiltration time,the greater the depth of infiltration,the smaller the migration distance of wetting front,the cumulative infiltration amount and the infiltration rate.The type and depth of the modifier affect the migration distance of the wetting front and the fitting model coefficient of the cumulative infiltration volume with time.The qualitative coefficient of the index(determined by the Horton model)is about 0.70,and the determinate coefficient of other models is above 0.97.In Kostiakov and Philip infiltration models,the fitting coefficients K and S gradually decreased with the increase of the application depth of the modifier.Among them,the fitting coefficients K in Kostiakov infiltration model decreased first and then increased with the increase of the application depth caused by silicone functional fertilizer and straw.Different improver and application depth affect the distribution of soil moisture content in soil depth.The soil water content decreased with the depth of soil.In the soil layer containing the modifier,the soil water content was greater than that of the control treatment.Under the same soil depth,soil water content increased gradually with the depth of amendments applied.Different improver and application depth lead to the change of salt content in soil depth.Under different application depths of silicone functional fertilizer,wheat straw,wheat decayed straw and calcium sulfate,the demarcation line between desalting zone and salt accumulation zone was about 12 cm,10cm,12 cm and 8cm,respectively.The depth of improver application affects the change of conductivity.At the soil depth of0?10cm,the soil conductivity gradually decreases with the deepening of the application depth of silicone functional fertilizer.When the soil depth is more than 10 cm,the soil conductivity will reach the maximum at the limit of the application depth,that is,the accumulated salt content will be the highest.wheat straw led to salt accumulation in saline-alkali soil,resulting in higher soil conductivity.With the increase of planting depth of wheat straw,soil conductivity also increased,which was greater than that of the control treatment.The soil electrical conductivity increased with the depth of wheat straw application.In the soil layer containing calcium sulfate,the soil electrical conductivity is less than that without calcium sulfate.(3)The effects of different amendments and layer application positions on soil infiltration characteristics and electrical conductivity are revealed.The closer to the surface layer of the soil column,the cumulative infiltration amount and the transport distance of wetting front decreased obviously.The effect of the layer location of the straw and the decomposed straw on the cumulative infiltration amount and the transport distance of wetting front was the most obvious.With the extension of infiltration time,the cumulative infiltration amount and wetting front migration between different treatments will be equal at a certain time.With the deepening of the layer application location of the modifier,the wetting front migration and time,rate and the fitting coefficient of the mathematical model of cumulative infiltration and time appear irregular changes.The distribution of soil moisture content was affected by different improver and layer application location.The soil moisture content above the layer application was significantly higher than that below the layer application.Compared with other ameliorants,The straw of wheat and decomposed straw made soil moisture accumulate more in the soil layer above the layer,so the soil water content increased more obviously.Different improver and location of layer application lead to the change of salt content in soil depth.Under different layers of silicone functional fertilizer,The straw of wheat,wheat decomposed straw and calcium sulfate,the demarcation line between desalting zone and salt accumulation zone was about 12 cm,12cm,10 cm and 10 cm in soil depth,respectively.Soil salinity was minimized by organic silicone functional fertilizer and maximized by The straw of wheat,wheat decomposed straw and calcium sulfate around layer application sites.