Impacts of reclaimed water irrigation on salt transport and composition in soil

Tao Mingxin; Liu Zhao; Ma Yan; Wang Jinfeng; Zhang Jiaqi; Wang Yuying; Zheng Xiaomin; Zhou Weibo

doi:10.13522/j.cnki.ggps.2025301

Abstract：[Objective]Reclaimed water has been increasingly used as a complementary irrigation resource to alleviate freshwater shortages,yet its effect on salt components and salt accumulation in soil is poorly understood.This paper aims to fill this gap through experimental investigation of salt composition and salt transport in soil under reclaimed water irrigation.[Method]The experiment was conducted in a reclaimed-water-irrigation area in Lintong District,Xi'an,where furrow irrigation is the dominant irrigation method.It consisted of three irrigation treatments:no irrigation,irrigation using groundwater and irrigation using reclaimed water.We analysed soil chemical properties in each treatment,and then used the Hydrus-1D model to simulate soil water and salt transport under three irrigation scenarios:2 925 m3/hm2(I1),3 525 m3/hm2(I2),and 4 050 m3/hm2(I3)to analyse their effects on salt migration.[Result]Salt content in the 40-60 cm soil layer under reclaimed water irrigation was 12.09%higher than that under non-irrigation and groundwater irrigation,and its associated chloride content was 76.69%and 65.49%higher than that of non-irrigation and groundwater irrigation,respectively.Compared with non-irrigation and groundwater irrigation,reclaimed water irrigation increased the total salt content in the 60-80 cm layer by 2.4%and 20.68%,and chloride content by 49.86%and 7.04%,respectively.No significant differences in sodium adsorption ratio(SAR)and pH were identified in the soils under different irrigation water sources.Overall,total salt content and chloride content in the 40-60 cm soil layer were higher,and SAR was lower than that in the 60-80 cm soil layer.Simulation results showed that the peak total salt content increased from 800 mg/kg to 815 mg/kg when irrigation amount increased from 2 925 to 4 050 m3/hm2.Our results showed that salt accumulated in the 60-80 cm layer earlier than in the 0-20 cm layer.[Conclusion]Reclaimed water irrigation elevated soil salinity,with the 40-60 cm layer showing more severe salinization than the 60-80 cm layer.Both peak salt content and downward migration of soil salt were positively correlated with irrigation amount.Precise irrigation management is thus required to mitigate secondary soil salinization.