| Water-retaining agent is a rapid development of chemical water-saving technology in recent years,which can enhance soil water retention,improve soil structure and improve water use efficiency.Water-saving production by soil water-retaining agent is an important way and method to alleviate water shortage.Northwest arid and semi-arid areas,water-retaining agent exposed to the oxidizing environment,will gradually break down caused by water-retaining agent failure.In order to prevent the failure of water-retaining agent,the effect of different surface water-retaining agent on soil water and salt migration was studied by combining soil surface sand and mixed water-retaining agent by using soil surface sand and oxygen.(1)Experiments were carried out by indoor simulated infiltration experiments only sand CK,Sand + water retaining agent 0.10%,sand coating + water retaining agent 0.20%,sanding + water retaining agent 0.50% and sandi ng + water retaining agent 1.00% in five modes of the characteristics for one-dimensional evaporation of soil moisture.The results showed that the application of water retaining agent in soil could decrease the wetting rate and infiltration rate of soil moisture,and the greater the concentration of water retaining agent,the greater the inhibitory effect.The advancing distance of the wet front is proportional to the time function: the cumulative infiltration at the same time is inversely proportional to the concentration of the water retaining agent,but the water retaining agent can extend the infiltration time and the longer the concentration is,the longer the infiltration time is.The cumulative cumulative infiltration amount is proportional to the water-retaining agent,the greater the concentration of the water-retaining agent,the greater the cumulative infiltration volume,the cumulative infiltration and the time power function: wet front and cumulative infiltration of a linear relationship;The relationship between seepage rate and time is consistent with the Kostiakov model.(2)Through the simulation experiment of soil column.experiments only sand CK,Sand + water retaining agent 0.10%,sand coating + water retaining agent 0.20%,sanding + water retaining agent 0.50% and sanding + water retaining agent 1.00% i n five modes of the characteristics for water and salt under constant Evaporation.The results showed that with the progress of evaporation,the water content of soil layer decreased gradually,but the water loss rate of sand layer and water retaining agen t was less than that of sand,and the water retention agent had the better water retention effect.After 30 days of constant evaporation,the soil water content was 30.61% and the water content of the soil was about 30% when the water retention agent concentration was 0.20%.The water retention agent concentration was 0.20%,When the concentration of water-retaining agent is less than 0.20%,the effect of inhibiting salt polygly increasing increases with the increase of water-retaining agent concentration.When the concentration of water-retaining agent exceeds 0.20%,the effect of salt suppressing is not obvious,so the concentration of water-retaining agent reaches 0.20 % Of the best results.(3)The effect of different concentration of water retaining a gent on soil water evaporation was studied by outdoor evaporation barrel experiment.The results showed that the cumulative evaporation of 0.10%,0.20% and 0.50% was 5.70%,20.20% and 25.65%,respectively,under the condition of no sanding.Under the condi tion of sand,the cumulative evaporation of soil without water retaining agent was 87.08% less than that of bare soil,When the concentration of water retaining agent was 0.1 0%,0.20% and 0.50%,the cumulative evaporation of soil water decreased by 90.47%,96.20% and 96.32% respectively.The results showed that the effect of water evaporation was basically the same as that of 0.20% and 0.50%,Among them,the concentration of water-retaining agent under sand was 0.20% and 0.50%,and the effect of water evaporation was not obvious.For this reason,the concentration of water-retaining agent was 0.20%.(4)The results showed that the particle size distribution of the soil changed with the change of the concentration of the water retaining agent.Under the elect ron microscope at 50.0μm,the soil particles were irregularly shaped,and the particle size and spacing of the soils with different water retaining agents varied greatly The The concentration of water retaining agent was negatively correlated with fractal dimension D,clay volume fraction and powder volume fraction,and positively correlated with sand volume fraction.The relationship between the concentration of water-retaining agent and the fractal dimension of soil particle size is quadratic polynomial. |
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