| Under the special natural conditions in Xinjiang,long-term irrigation under drip irrigation under film can only leaching salt from the soil to the vicinity of the root layer of the crop,damage to crop root growth and development,resulting in crop production and even secondary salinization of soil,long-term implementation also changed the traditional spatial distribution of soil water and salt,so that there is a new spatial distribution pattern of farmland soil water and salt.Therefore,this study is based on field monitoring experiments and laboratory tests,using traditional statistical and geostatistical methods to analyze the spatial variability and spatial distribution pattern of soil water and salinity in long-term continuous cotton cropping under drip irrigation under film.The purpose of this study is to provide a preliminary understanding of soil and soil moisture characteristics in long-term continuous cotton cropping under drip irrigation under film,and a preliminary understanding of the spatial variability and spatial distribution of soil water and salinity,in order to provide theoretical guidance for the treatment of farmland soil salinization and sustainable cultivation of farmland.The preliminary research results are as follows:(1)The main texture of the surface soil in the study area is loam,sandy loam and silty loam,sand is the main component of the surface soil in the study area.The combination of VG model and RETC software is suitable for the prediction of VG model parameters such as?_s,?,n in the study area.Soil sand,silt,clay content and soil bulk density have a great influence on the values and spatial distribution of VG model parameters?_s,?,n.(2)The spherical model is more suitable for fitting the variogram model of soil moisture in the study area,the spatial distribution of the soil moisture content in the north and south of different monitoring years in the growth period is relatively good.Both the values of salt content and the spatial variability of randomness are declining year by year,the salinity of all soil layers shows a decreasing pattern from south to north as a whole,the southern and northwestern parts of the study area had high salt content areas,salt is mainly accumulated in the depth of 40-100cm soil layer.(3)With the passage of years,influenced by the topography and irrigation methods in the study area,the soil moisture content and salt content within the depth of 40-100 cm both have inter-annual migration and begin to decrease along the soil depth.The salt content in high-value areas in the northwest decreases year by year,indicating that most of the salt in the cotton fields can be discharged from the cotton fields to the salt drains.(4)The moisture content in different periods of growth period increased along the soil depth,and the high moisture content areas were mainly distributed in the southern part of the study area.The change gradient was more obvious,and the soil moisture content in July was more evenly distributed than in April and October.The salt content of soil in all periods was distributed along the north-south direction.The salt content of all soil layers was basically the highest in April,indicating that the spring salt return effect has a great influence on the salt content in April.(5)Under different scales,the soil moisture content is the smallest in the 0-20cm soil layer,and the water content increases with the increase of soil depth,and the spatial distribution tends to be uniform as the scale increases.The spatial variability of salt content in 20-40cm soil layer is the strongest.With the passage of growing period,the time stability of salt in different soil layers at different scales is significantly different,the time stability of salt distribution in 0-20cm soil layer is higher than that of other soil layers.With the increase of soil depth,the time stability of salt distribution at each scale began to decrease,and on a smaller scale,the time instability became more pronounced. |
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