Transport And Management Of Soil Water And Salt Nutrients In Typical Critical Zone On The North Slope Of Tianshan Mountains

Object:There are complex material cycle and energy exchange in the critical zone but also fragility and instability.One of the main limiting factors of agricultural development in the critical zone on the north slope of the Tianshan Mountains is water resource.Mountainous,piedmont and oasis-desert transition landscapes are common in arid areas and provide important ecosystem services and human well-being for regional economic development.However,the vertical distribution and spatial distribution of soil water,salt,and nutrients in different landscape environments and their driving forces are still unclear,thus causing a series of soil pollution,ecological damage,and other problems.Therefore,exploring the migration and distribution law of soil water,salt,and nutrients and proposing corresponding soil management measures can provide a basis for farmland management in this region.Methods:In this study,the 0-60 cm soil layer in the critical zone on the north slope of Tianshan Mountain was selected as the research object,and different geomorphic types were divided.Stratified soil sampling and laboratory analysis were combined.Using hydrogen and oxygen stable isotope methods,the vertical migration rules of water,salt and soil nutrients of different geomorphic types in the critical zone on the north slope of Tianshan Mountain were summarized through stratified soil sampling,and the influencing factors were clarified.Soil management strategies and suggestions were provided from vertical soil stratification and spatial layout of different geomorphic types.Results:（1）The soil bulk density of different geomorphic types fluctuated first and then tended to be stable,while the spatial variability of soil p H was insignificant.Soil salt content was stable in different geomorphic types.The variation ofδ¹⁸O andδD isotopes in soil surface soil is the most obvious.From the perspective of spatial distribution,δ¹⁸O andδD isotopes in the soil in the oasis area are stable.（2）Because soilδ¹⁸O andδD isotope values were affected by drip irrigation under the film for a long time,the slope and intercept of the linear fitting equation reflected by different soil depths were smaller than that of the atmospheric precipitation line in the study area.The slope and intercept of the linear fitting equation of isotope values decreased gradually with the increase of soil depth.（3）Soil total nitrogen,alkali-hydrolyzed nitrogen,available phosphorus,and available potassium in the Manas River basin on the north slope of the Tianshan Mountains were positively correlated,and the contents of soil total nitrogen and alkali-hydrolyzed nitrogen were higher near mountain areas.The contents of alkali-hydrolyzed nitrogen,available phosphorus,and available potassium increased with the increase of total nitrogen content in mountain-in front of the mountain-oasis-desert soil.The main influencing factors are different geomorphic types,fertilizer application amounts,and irrigation amounts.Soil temperature and humidity would affect the variation of soil available nutrients.（4）The main management measures of vertical soil stratification are to increase the application of organic fertilizer,rational irrigation,and maintain soil moisture content.In the shallow root layer,plant root distribution shallow,should be appropriate to reduce artificial plowing.Soil management measures of different geomorphic types are mainly to reduce soil erosion and soil erosion,dry soil,and poor water retention and storage capacity of the soil,so irrigation frequency should be increased.Long-term cultivation of farmland can adopt the form of intercropping,and crop planting should be appropriate,paying attention to spacing,and avoid nutrient deficiency and uneven distribution,to improve the spatial distribution of soil nutrients.Conclusion:Soil vertical water isotope values showed a trend of fluctuation and increase.Soil salt content was stable in different geomorphic types.The variation trend of available nutrients in 0-20 cm soil was obvious,and that in 20-60 cm soil was gentle.The main management measures are to increase the application of organic fertilizer in appropriate amount,carry out irrigation reasonably,maintain soil moisture content and reduce soil erosion.It provides a reference for rational utilization of water resources,protection of farmland soil,local economic development,and ecological protection.