| Our country has abundant reserves of brackish water.Proper use of brackish water can improve agricultural irrigation efficiency and effectively alleviate local water resource shortage.However,improper use of brackish water will lead to accumulation of salt in the soil,resulting in soil salinization.The method of covering the soil surface with straw and adding straw interlayer to the soil can effectively improve the soil structure,improve the soil fertility,maintain the moisture content in the soil,and inhibit the phenomenon of salt surface accumulation.Therefore,this paper carried out indoor soil column infiltration and evaporation tests.Sunflower straw in sunflower planting base in Lanzhou New Area was selected as the research object,and the local soil was treated by surface covering and straw interlayer,and the differences of water and salt migration laws in soil after brackish water irrigation under different straw treatments were compared.The experiment was divided into three stages:In the first stage,pure water was used to infiltrate two kinds of straw(powder and fine rod)treatment groups to determine which form of straw was more conducive to water infiltration;In the second stage,the optimal straw form(powder)was selected for surface covering,10cm depth separation and 20cm depth separation,and the brackish water with different salinity(0g/L,2/L,4/L,6/L)irrigation was used to analyze and compare the effects of different straw treatments and different concentrations of brackish water on soil water and salt migration.In the third stage,evaporation tests were carried out on soil columns after the completion of infiltration to explore the influence of different straw treatments on the inhibition of water evaporation in soil and the change of water and salt distribution in the vertical direction.The main research results are as follows:(1)the first phase of research results in powdered straw and thin rod experiment,the two groups of straw stalk interlayer burying depth for the migration velocity of wetting front in the soil are affected in some way.In the powdered straw group,table cover treatment to slow the progress of the wetting front migration velocity is minimized,infiltration time than the control group increased nearly 60min,(16)0cm depth layer separation treatment than the control group increased 120min,20cm depth layer separation treatment of the wetting front migration inhibitory effect is most obvious,infiltration time increased nearly200min;Infiltration in the late stage in the thin rod straw group,(16)0cm depth interlayer group and 20cm depth interlayer infiltration rate is close to,were similar,control group than the pure soil infiltration to complete the time required to increase(16)50min and 180min,inhibitory rate of the conveyance speed of wetting front 31.3%and 37.5%.Through on the relationship between the cumulative infiltration amount and time of the fitting results show that two kinds of straw treatment is more suitable for Kostiakov model,and the cumulative infiltration and wetting front exists good linear correlation between.The powdered straw is more hydrophilic and has a stronger adsorption capacity for water,so it is more obvious to judge the degree of influence of the wetting front advance velocity by the separation layer.After comprehensive consideration,the powdered straw which is more conducive to data analysis is selected to carry out the subsequent infiltration and evaporation test.(2)The results of the second stage:the soil was treated differently with powdered straw.In the infiltration test,it was found that different depth layer treatments had significant effects on wetting front migration and cumulative infiltration in the soil.choose(17)g/L salinity of brackish water infiltration in soil depth for 20cm add straw barrier processing is more than the group without interlayer infiltration time around(18)00min.(16)0cm amount of cumulative infiltration depth straw layer separation treatment group is the largest.Migration and accumulation of wetting front infiltration amount and the function relation between time can respectively with Z_f=mt~nand Kostiakov model,and the wetting front migration with good linear relationship between cumulative infiltration amount.The interlayer zone increases the overall moisture content of the soil profile,and the soil has better water retention ability.Moreover,the salt content of the whole soil column profile changes,and a large amount of salt accumulates in the interlayer zone.In range of(15)cm-50cm,(17)g/L salinity,with CK2 group compared to reduce the conductivity of the highest S2G1 group achieve 20.6(4).(3)The results of the third stage:In the evaporation test after the infiltration test,it was found that different depth layer treatment had different effects on the distribution of cumulative evaporation,soil profile water content and salt content.With different interlayer treatment group of evaporation time for15 days,including pure water irrigation,without placing straw in treatment group after group cumulative evaporation to 96.33mm,0cm treatment group,10cm treatment group,20cm treatment group of cumulative evaporation is 37.8mm,62.11mm,87.55mm;Three treatment groups,respectively than no straw cumulative evaporation in the control group,respectively,to reduce60.78(4),35.53(4)and 9.11(4);With concentration for(17)g/L of brackish water infiltration treatment group after the evaporation 15 days,the highest average moisture content in soil column is 0cm treatment group,10cm treatment group and the 20cm treatment group take second place,in the control group the lowest average moisture content in the soil column.The change of moisture content in soil has an effect on the distribution of salt content in soil body.The straw separation prevents the evaporation of water,but also inhibits the migration of salt to different degrees. |
