A Study On The Movement Characteristics Of Soil Moisture And Salt Content And Nitrogen Content And Cotton Growth In Xinjiang Farmland

Soil salinization has become one of the main limiting factors restricting the sustainable development of agriculture in Xinjiang.In order to clarify soil water,salt and nitrogen transport and cotton growth characteristics,the paper adopts a combination of regional survey,experimental analysis and simulation analysis to analyze the distribution characteristics of soil water,salt and fertilizer in different planting areas at large scale,the growth characteristics of cotton,and soil water and salt Based on the spatial variability of nitrogen,establish a soil nitrogen balance model and optimize irrigation schedules.The main conclusions are as follows:(1)Analyze the spatial variability of soif physical parameters and water,salt and nitrogen parameters in the study area.The soil bulk density Cv value is between 0.01 and 0.1,which belongs to the degree of weak variation.The variation between each layer is small and the soil bulk density is consistent.Variations of clay particles,powder particles,and sand particles are moderately weak.The Cv value shows that clay particles>sand particles>powder particles.The spatial correlations are all less than 20%,which is a strong spatial dependence.The semi-variance functions of clay,silt,and sand can be fitted with Gaussian models;the semi-variance functions of soil bulk density at 20 and 60 cm conform to the exponential model,at 40 cm.The bulk density conforms to the Gaussian model.The soil water content in the whole area belongs to moderate variation,and the Cv value in the wasteland area>fruit tree area>cotton field area.4.The semi-variance functions of soil water content in September and September all conform to the Gaussian model.Compared with the semi-variance functions of soil water content in the same period in 2018,it shows that the distribution structure of water content is similar and can all meet the distribution characteristics of the Gaussian model.The coefficient of variation of soil salt content Cv value Wasteland area>Cotton field area>Fruit tree area,most cotton fields are in the state of salt accumulation,the amount of salt accumulation is greater than the salt accumulation of fruit tree area,and the semi-variance function model Gaussian and exponential model are analyzed.The soil nitrate nitrogen content in cotton fields and fruit tree planting areas belongs to a moderate variation degree,while the ammonium nitrogen content change belongs to a moderately strong variation degree,but all are analyzed using Gaussian models.(2)The soil nitrogen transfer model is established based on the measured data,and the simulation effect is better.According to the simulated nitrogen absorption,the nitrogen use efficiency is calculated to be 47.7kg/kg.Compared with the nitrogen use efficiency of 44.9kg/kg in 2018,it is basically kept at the same level.Cotton is basically not under nitrogen stress,while soil water use The efficiency is 1.10kg/m3,and the water stress during the critical growth period is less.(3)The plant height,leaf area index,and biomass of cotton in the study area can be simulated using the modified Logistic model,and the parameter changes are small between different years.The growth indexes of cotton in the study area are positively correlated,and the amount of salt accumulation and biomass are negatively correlated.(4)Using the AquaCrop model to simulate and analyze the effect of irrigation volume and initial root layer salt concentration on cotton yield,it is shown that when the irrigation amount reaches 350m3/mu?400m3/mu,the yield basically reaches the peak,and the initial root layer salt concentration is 5?10ds/cm,the output is relatively similar.The Saltmodel model was used to analyze the characteristics of irrigation volume and irrigation water quality on root layer salinity and groundwater level,and it was found that the salt accumulation in the root zone with an irrigation volume of 250m3/mu in 1 to 6 years was more effective;The effect of salt pressing is better,and the salinity is significantly higher in 6-10 years.For high-salinity areas,under the basis of 300m3/mu of irrigation,fresh water can be used for irrigation after 3 to 4 years.For low-salt areas,the irrigation water quality increases from 1g/1to 3g/1 for freshwater The simulated value fluctuates from-74%,-44%,-14%,and 15%from the initial salt change in the root zone of the soil.