| The rational development and use of brackish water has important practical significance for solving the shortage of water resources and the efficient utilization of agricultural water.However,the unreasonable use of brackish water will make the soil accumulate salt and cause salinized soil.When using brackish water,it is necessary to formulate reasonable irrigation system and appropriate farming measures in order to make brackish water play a better role.Straw returning to the field can improve the soil structure and inhibit the accumulation of salt on the surface.Sand covering can better improve the infiltration capacity of soil water and retain water.In view of this,the indoor soil column infiltration test is carried out in this paper.For cultivated soil and native soil,a mixing layer(straw mixed with sand)is set on the soil surface,the thickness of sand is set as(0cm,3cm,6cm,9cm),the proportion of straw is(1%,2%),and the brackish water with different salinity(0g/L,1g/L,3g/L,5g/L)is used for irrigation.At the same time,the soil water characteristic curve of two kinds of soil and straw mixed with different proportion in sand are measured,The effects of different mixing treatments and brackish water irrigation with different salinity on soil water and salt transport were compared and analyzed.The research contents and conclusions of this paper are as follows:(1)The soil water characteristic curves of two kinds of soil and sand mixed with 1%and2%straw were measured respectively.The results show that the soil moisture content of the two soils under the same suction is:sandy clay loam>sandy loam.The moisture content of straw mixed with different proportion in sand under the same suction is as follows:sand+2%straw>sand+1%straw.At the same time,the salinity of brackish water has little effect on the water characteristic curve of two kinds of soil mixed with different proportion of straw in sand.(2)The infiltration test was carried out on soil columns under different mixing treatments under brackish water irrigation,and the results showed that:The mixed layer can improve the water infiltration capacity of sand-clay loam and promote the migration of wetting front.It takes less time for sandy loam to infiltrate to 40cm;2%straw blending time is longer;when1g/L,the mixed layer shows an inhibitory effect,but it can reduce deep leakage,and when3g/L,the mixed layer shows for promotion.For both soils,the relationship between wetting front and time can be well fitted by the power function Z_f=mt~n.No matter 3cm,6cm and 9cm straw blending treatments can increase the cumulative infiltration of the two soils,the fitting results of the cumulative infiltration and time show that both soils are more suitable for the Kostiakov model.The wetting front of the two soils had a good linear relationship with the cumulative infiltration.Mixing layer treatment can alleviate the supersaturation phenomenon of sand-clay loam soil surface.When the salinity is 1g/L and 5g/L,6cm sand mixed with straw;when 3g/L,3cm sand mixed with straw makes the soil moisture content higher.High,good water retention.The water content of sandy loam is lower than that of sandy clay loam.(1g/L)6cm sand mixed with straw;(3g/L)3cm sand mixed with straw;(5g/L)9cm sand mixed with straw can increase the soil moisture content.Conducive to crop growth.The surface conductivity of sand-clay loam soils mixed with 3cm and 6cm straws was lower,which could inhibit the accumulation of salt.The deep salt removal effect of 2%straw blended was better.Under brackish water irrigation,the soil profile conductivity of 6 cm sand mixed with 1%straw was lower.At 3g/L and 5g/L,mixing 6cm and 9cm sand can better reduce the surface salt content of sandy loam soil.(3)The infiltration test was carried out by using the soil column covered with different salinity underwater straw mixed with sand,and the results showed that:When the salinity is3g/L and 5g/L mixed with 3cm sand and straw,and 9cm sand mixed with straw,the wetting front and cumulative infiltration of sand-clay loam are both promoted,and at 1g/L,it is inhibited.Wetting front migration and cumulative infiltration.Under the mixing of 6 cm straw,no matter how much the salinity of the brackish water is,it can promote the wetting front and increase the cumulative infiltration.For sandy loam soil,when 9 cm of sand is mixed,the higher the salinity is,the more obvious the promoting effect of the wetting front is.The use of3g/L brackish water can improve the overall water content of sandy clay loam under the blending of 3cm and 9cm straws.Under the blending of 6cm straws,the higher the salinity,the higher the moisture content.The use of brackish water to irrigate under the mixing of 3cm and 6cm straw can increase the average water content of the sandy loam soil 8-24cm soil layer,which has a positive effect on the water absorption of plant roots.Under brackish water irrigation,the surface salinity content of sandy clay loam can be reduced,and the leaching effect is very good.The higher the degree,the better the salt control effect.The sandy loam soil was irrigated with brackish water and mixed with 6cm and 9cm straw to reduce the salt content in the upper layer of the soil. |
