Study On The Influence Of Bulk Density And Super Absorbent Polymers On Two-Dimensional Transport Of Soil Water And Salt

In recent years,super absorbent polymers(SAPs)have developed rapidly as a chemical water-saving material.Because it has a good water storage and protection function,its application in the arid regions of the northwest can not only greatly alleviate the shortage of local water resources,but also make crops increase production and income.While SAP can improve the utilization efficiency of soil water,it is placed in the air for a long time,and a redox reaction occurs,which causes the SAP to fail in the arid regions of northwest China.Sand mulching above the soil layer mixed with the SAP can block the influence of light and air on the water retaining agent,thereby suppressing the failure rate of the SAP.The SAP is uniformly mixed into the surface layer(0-5cm)soil,and the sandstone is mulched on the SAP mixed layer.The infiltration rate,cumulative infiltration,electrical conductivity,wetting front transition distance and the change of wettability trait with infiltration time were studied during the two-dimensional infiltration process of point source under the condition of different soil bulk density and the amount of SAP.(1)Two-dimensional infiltration test of soil water was carried out indoors,and it was concluded that the soil water infiltration characteristics were affected by the amount of SAP and sand and gravel coverage.The results showed that whether the sand and gravel were mulched above the SAP mixed layer did not affect the law of the amount of SAP on the infiltration characteristics of soil water.The infiltration rate was negatively correlated with the amount of SAP.The cumulative infiltration amount was positively correlated with the amount of SAP.The distance of the wetted body in the lateral direction increased with the increase of the amount of SAP,and the distance in the longitudinal direction decreased with the increase of the amount of SAP.The aspect ratio of soil wetted body increased with the increase of the amount of SAP.The Kostiakov infiltration model was used to verify the relationship between cumulative infiltration and infiltration time,and there was a power function relationship between the two.(2)Two-dimensional infiltration test of soil water was carried out indoors,and it was concluded that the soil water infiltration characteristics were affected by the amount of SAP and sand and gravel coverage.The results showed that when the SAP was not added,the lateral displacement distance of the wetting body was smaller than the longitudinal displacement distance.When the SAP was added,the transverse displacement distance of the wetting body was greater than the longitudinal displacement distance;the transverse infiltration rate was positively correlated with the amount of SAP,and the longitudinal infiltration rate was negatively correlated with the amount of SAP;the bulk density promoted the lateral water transfer distance and inhibited the longitudinal water transfer distance;the ? value of the soil was generally negatively correlated with the bulk density.The value of ? first increased rapidly and then increased slowly and then stabilizes.When the SAP was applied,the value of ? was always less than 1.(3)After the end of the soil water infiltration test,under the conditions of gravel-mulching and non-gravel,the influence of soil bulk density and the amount of SAP on the conductivity of soil wetted body was obtained.The results showed tha t when the SAP mixed layer(0-5cm)the sand and gravel were not mulched,the salt changed to the maximum with the water to 19 cm.When mulching the sand and gravel,the salt changed to the maximum with the water to 22 cm;when the depth of the soil layer was 5-10 cm,the salt changed to the maximum with the water up to 19 cm;when the depth of the soil layer was 10-15 cm,the salt changed to the maximum with the water up to 16 cm.The conductivity decreased with the increase of the amount of SAP,and the decrease of conductivity was positively correlated with the amount of SAP;the difference in conductivity between the sampling points was not large in the soil layer with a depth of 10-15 cm.