| Saline-alkali soil is a widely distributed soil type in China,which is also an important reserve land resource.To properly improve and develop saline-alkali soil based on local conditions is highly related to regional economic development and ecological security construction.In this research,aiming at the bottleneck problems of heavy texture,high degree of salinization and difficult salt leaching in alkalized solonchak soil in Jingyuan,Gansu Province,the dynamic changes of water and salt in soil and groundwater were monitored in situ to define the dynamic relationship between groundwater and soil water-salt.The indoor soil column simulation tests were carried out to study the effect of soil water infiltration,and select the best ameliorated technology.Through field location test,studies on the effects of the application of ameliorated materials,different planting methods and irrigation quota,as well as salt-tolerant plants on water-salt transport and water-salt regulation in alkalized solonchak were further carried out.The main conclusions are as follows:(1)In-situ monitoring on water-salt dynamics of alkalized solonchak soil and the depth,mineralization of groundwater shows that:the soil salinity of alkalized solonchak in this area decreases with the increase of groundwater depth,and there is an exponentially relationship between soil salinity and groundwater depth.The soil salinity of alkalized solonchak in this area increases with the increase of groundwater salinity,and there is a linearly relationship between soil salinity and groundwater salinity.On this basis,the relationship between soil salinity of alkalized solonchak and groundwater mineralization and depth in the arid area of Jingyuan,Gansu Province was established,which provided a reference for analyzing the relationship between soil salinity and groundwater in this area.(2)Study on the effects of desulfurization gypsum(DG)and straw cushion on alkalized solonchak soil shows that:after adding desulfurized gypsum to alkalized solonchak soil,the soil exchangeable sodium percentage(ESP)and salinity in 0-60 cm soil layer decrease by 22.7%and 48.6%on average compared with initial soil.The infiltration rate,depth of wetting front and cumulative infiltration volume are all larger than the controlled site(no DG)at the same time.After setting up the straw cushion to alkalized solonchak soil,the soil ESP and salinity in 0-60 cm layer decrease by 8.8%and 58.9%on average compared with initial soil.Desulfurization gypsum combining straw cushion can reduce the soil ESP and salinity of 0-60 cm soil by 26.8%and 65.0%on average compared with initial soil.The combination can effectively reduce the soil ESP and salinity of alkalized solonchak soil,and is an effective way to ameliorate typical alkalized solonchak soil.(3)Study on the effects of ameliorated materials on water-salt transport and regulation in alkalized solonchak soil shows that:improved materials,irrigation and leaching influence the soil water-salt and ions changes.The water-salt of surface soil changes significantly,and the soil moisture and salt content are low in 0-20 soil layer.The soil water-salt changes in 40-100 cm soil layer are stable.The application of desulfurization gypsum can reduce the content of Na+,HCO;and CO32-.Na+migrates downwards in a "stepped pattern",while Ca2+,K+,Mg2+,Cl-and SO42-migrate downward in a "wave-like" pattern,and HCO3-;and CO32-migrate downward in a"corrugated" pattern.(4)Study results on the effects of amorpha different planting methods on alkalized solonchak soil show that:based on the uniform application of ameliorated materials,compared with the non-ridging treatment,the soil salinity,ESP and pH value of ridges and furrows planting treatment in 0-60 cm soil layer decrease by 14.2%,15.4%and 9.8%,respectively.And the survival rate of amorpha increase by 12.7%compared to the non-ridging treatment.Planting amorpha through ridging furrows in alkaline saline soil can help to reduce the salinity and ESP of soil in ridges and furrows and improve the ameliorated effect.This technology provides a new method for vegetation restoration of alkalized solonchak.(5)Study on the effects of different salt tolerant plants on the micro-area water-salt regulating in alkalized solonchak soil shows that:based on the uniform application of ameliorated materials to alkalized solonchak soil,planting salix matsudana '9901',amorpha and irisensata thunb can increase surface coverage and reduce evaporation.The coverage of three plants in the second year is 73.7%,78.4%and 83.1%,respectively.The soil salinity in the 0-60 cm soil layer decrease by 34.7%,36.6%and 42.0%,respectively,compared with the treatment without planting.The coverage rate of planting irisensata thumb is highest,with the lowest rate of secondary salinization. |
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