Effects Of Sand Distribution On Water Properties Of Clay Saline Soil

This study is aimed at solving the problems of soil salinization,texture stickiness,difficulty in soil drainage and salt drainage in the Yellow River Delta,combined with the problem of sedimentation of the Yellow River sediment and high cost of dredging.Materials,experiments and research on the improvement mechanism of coastal clay soil were carried out.Through the indoor analysis,model simulation and field experiment,the soil moisture characteristic curve test under different sand content was designed,and the different sand content was determined.The effect of sand distribution on the improvement of coastal clay soils was studied by the effects of soil particle gradation,soil water characteristic curve,soil water content,soil water availability and motility on the saline soil.The main conclusions are as follows:(1)The composition of the yellow sediment and the clay soil is obviously different.The highest proportion of the fine sediment in the yellow sediment is 0.1-0.05mm,the value is63.40%,and the most proportion in the clay soil is 0.05-0.01mm coarse powder has a value of48.05%;the sand content can significantly increase the sand content in the clay soil and reduce the clay content in the soil,thereby improving the soil texture.(2)The VG model in RETC software was used to fit the soil water characteristic curves under different sand distributions.The results showed that the soil water characteristic curves of different soil particles after sand matching reached a high degree of fitting,and the correlation coefficient was>0.999.The results show that under the same water suction,the change of soil water content under different particle composition is that the more sand content,the larger the number and proportion of macropores,the easier the water is removed,the weaker the water holding capacity of the soil remains.The less moisture there is.(3)With the increase of sand content,the saturated water content,soil capillary water holding capacity,field water holding capacity and wilting coefficient of the soil showed a significant decrease trend.From 36.61%,32.88%,23.15% to 30.79%,13.55%,3.00%,respectively,a linear negative correlation;Both the ineffective water content and the effective water content showed a trend of decreasing first and then decreasing significantly,from 8.77% and 14.38% to 0.38% and 3.59%,respectively.The results show that the increase of sand content in soil can effectively reduce soil water content,weaken soil water holding capacity and increase soil aeration.(4)With the increase of sand content,the effective water and difficult water content in the soil decreased significantly,which decreased from 13.65% and 10.45% to 5.27% and 0.20%,respectively,which were negatively correlated with the amount of sand.The rate of reduction of the effective water content is less than the rate of reduction of the difficult water content,and the proportion of the effective water content increases from 56.62% to 96.34%,The results show that the more the sand content,the weaker the soil's ability to adsorb water,and the higher the proportion of water that is easily absorbed by plants;The amount of soil macropores and the soil gravity water content increased from 4.61% and 13.46% to 13.99% and 27.79%,respectively,which is beneficial to soil drainage and salt drainage,and can effectively reduce the salt content in the soil while saving water.(5)After field trials with sand,the water content of the 0-20 cm soil layer decreased significantly in the autumn of 2016 and spring 2017.Both of them decreased the S3 treatment most,which was 21.10% and 30.71% lower than that of CK;In the spring 0-20cm soil layer in the spring of 2017,when the S2 treatment was 10kg/m~2,the soil salinity decreased most significantly,which was 24.26% lower than S0.The above research shows that sand modification can improve the composition of clay soil particles,improve soil texture,increase the number of macropores in soil,improve soil aeration,reduce soil water content,and effectively improve soil water availability and motility.Conducive to soil drainage and salt discharge,with good improvement effect,the most suitable sand content is 10kg/m~2.