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Characteristics of Soil Water and Salt Movement for Water Repellent Soilunder Saline Water Irrigation

Author: SongHongYang
Tutor: LiYi
School: Northwest University of Science and Technology
Course: Hydraulic Engineering
Keywords: hydrophobic infiltration soil water movment salt distribution
CLC: S152.7
Type: Master's thesis
Year: 2013
Downloads: 2
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Abstract


Water repellent soil has special soil hydrodynamic characteristics. the existenceof water repellence is harmful to agricultural production and invironment protection.International scholars have studied soil water repellency for many years, whiledomestic study is just starting in recent years. But in general, most of the studys arefocus on the reasons cause soil repellency and the remedation measures for repellentsoi, few thesises are study the whole process of infiltration, especially the domesticstudy of soil water and salt movement of water-repellent soil is still not mature.Irrigated by fresh water and saline water on repellent soil, cumulattive infiltration,infiltration rate, wetting front and soil moisture distributions were compared the soilwater distribution and salt distribution on profile. The results showed that:(1)Sgnificant differences exist in infiltration characteristics betweenhydrophobic soils and hydrophilic soils. The infiltration rates of hydrophobic soilschanged at certain time points during infiltration, the time points were used to dividethe infiltration progress into fore-stage and post-stage; Kostiakov equation was foundbetter than the other models to describe the fore-stage I-t relationship while linermodel can describe the post-stage I-t relationship better during infiltration ofhydrophobic soils. The straight slope between wetting front depth and theaccumulation infiltration of hydrophobic soils decreases at a certain time point,water-holding capacity increase; the soil moisture content of hydrophobic soil inupper-layer is higher than hydrophilic soil.(2)Like hydrophilic soil,the infiltration ability can be enhanced by using salinewater irrigation in hydrophobic soil, the influence varies in different soils. Insaline-alkali soil and sand soil,6g/L saline water can improve the infiltration abilityobservably, but in Lou soil and shangjiang black soil,1g/L brackish water is moreefficient.(3)An obvious salt leaching happened in016cm depth at hydrophilicsaline-alkali soil profile, soil salt content increased when using higher salinity water to irrigate, but below16cm, all salinity water caused soil salt accumulation and watersalinity showed no significant effect on salt content; soil salt content is related towater salinity in hydrophilic lou soil, sand soil and shajiang black soil, and soil saltincrease will happen on all profile when used3g/L or6g/L salinity water to irrigate.(4)The hydrophobic soil salt and ions distribution on soil profile is similar withhydrophilic soil, but still have some differences. Compared with the same typehydrophilic soil, the depth in which soil salt and ions accumulation happens is lowerin hydrophobic saline-alkali soil. Hydrophobic lou soil and shajiang black soil hadlower soil salt content than the same hydrophilic soils, and the difference increasewith infiltration water salinty increase. The sand soil is hydrophobic or not has nosignificant impact on soil salt content; Cl-leaching and accumulation almost happenesin the same depth in hydrophobic and hydrophilic saline-alkali soil, except6g/L salinewater treatment, Cl-accumulation content is higher in hydrophobic saline-alkali soilprofile. For lou soil, sand soil and shajiang black soil, Cl-content is higher inhydrophobic soils, the increase in higher water salinity (3g/L and6g/L) treatment ishigher than lower water salinity (0g/L and1g/L) treatment; Ca2+content ofhydrophobic saline-alkali on lower depth (010cm) is higher than hydrophilicsaline-alkali soil, and the Ca2+content increase is significant under6g/L saline watertreatment. But in the depth of1020cm, Ca2+content of hydrophobic saline-alkali soilis lower than hydrophilic saline-alkali soil, and from20cm to the wetting front depth,Ca2+content converge to a same volume. Hydrophobic Lou soil and sand soil havehigher Ca2+content than Hydrophilic soils after saline water infiltration, but the Ca2+content between hydrophobic and hydrophilic Shangjiang black soil was almost thesame.

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CLC: > Agricultural Sciences > Agriculture as the foundation of science > Soil > Soil physics > Soil moisture
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