Study On Interspecific Water Distribution Of Jujube-cotton Intercropping System In Arid Oasis Region

The agriculture and forestry composite system is an important part of the infrastructure construction of the characteristic forestry and fruit growing industry in Xinjiang.The jujube-cotton intercropping pattern,as one of the types of agroforestry system,is widely used in the local area.However,the water consumption pattern of the jujube-cotton intercropping pattern is unclear,the irrigation system is not perfect,and crop yields are plentiful.Therefore,based on the theory of interspecific water relations,this study explored the interspecific water allocation relationship of jujube-cotton intercropping intercropping system,and clarified the evapotranspiration of jujube-cotton intercropping system,which is of great significance for scientifically formulating irrigation systems and guiding the development of local forestry industry.In this paper,through potted and field experiments,the jujube cotton intercropping system as the research object,using carbon stable isotope method,thermal diffusion method and micro-vaporometer method,the characteristics of temporal and spatial changes of soil moisture in jujube / cotton intercropping system,The inter-species water distribution relationship and evapotranspiration were studied and the following main conclusions were obtained:(1)The soil moisture of jujube-cotton intercropping system showed obvious temporal and spatial changes.In the vertical direction,the variation coefficient of soil moisture showed a downward trend with the increase of soil depth,with the largest surface layer and the lowest layer.In the horizontal direction,the soil water dissipated between the monocropping model lines has an exponential function.The closer to the jujube tree,the greater the evapotranspiration intensity.The maximum distance between trees is 50 cm,and the power is 50 cm.The intercropping pattern was affected by the placement of the drip tape,and the soil moisture consumption was wavy,with the peak at 25,100,and 150 cm from the tree.(2)Intercropping model evapotranspiration and soil water coefficient of variation were all lower than the monocropping model.The intercropping model could improve soil water stability,reduce soil moisture dissipative intensity,and increase soil water storage.Compared with adequate irrigation(Z2M2),only 50% irrigation(Z1M2)of jujube trees was reduced,and intercropping system evapotranspiration was reduced by 20.14%;only 50% irrigation of cotton(Z2M1)was reduced,and intercropping system evapotranspiration was reduced by 16.44%.Jujube trees have a greater influence on intercropping systems than cotton.(3)The water distribution system of jujube-cotton intercropping system was analyzed using validated carbon stable isotopes,stem flow,micro-vaporization apparatus and other methods.The results showed that the water use efficiency of cotton monocropping was higher than that of intercropping;the water use efficiency of jujube tree was lower than that of intercropping.The transpiration rate of single jujube trees was 1.02 times that of intercropping jujube;the transpiration volume of monocropping cotton was 0.88 times that of intercropping cotton.The ratio of transpiration of jujube and monocropping cotton was 0.82:1.The ratio of intercropping jujube and intercropping cotton was 0.71:1,accounting for 41.32% and 58.68% respectively.It can be seen from the ratio of transpiration at each stage of jujube intercropping that the ratio of jujube/cotton transpiration between June 11 and August 30 is between 0.87 and 1.19;jujube trees from June 11 to August 30 The ratio of cotton transpiration was 0.48 to 0.59,indicating that in the intercropping pattern,cotton dominated from June 11 to August 30.Jujube trees dominate at other times.(4)Single cropping jujube and cotton evapotranspiration were simulated using the double crop coefficient method.The results show that the simulated values are in good agreement with the measured values,and the jujube and cotton simulation results are excellent in 2016 and 2017.When the Kc weight ratio was used to simulate the intercropping,the Z2M2 treatment in 2016 was excellent for the simulation results,and the other treatments in 2016 and the three treatments in 2017 all had good simulation results.Therefore,the model estimates the evapotranspiration of the jujube-cotton intercropping system in the arid area with little error and has good applicability.Based on the double crop coefficient method and the comprehensive method,the water balance method simulation error was evaluated respectively.It was found that when the crop coefficient of cotton and jujube deviate from a large degree,the degree of impact on the intercropping compound system simulation is relatively high,so that the double crop coefficient method in May.Late-to-late June,the simulation accuracy is poor.However,jujube trees undergo water control,and soil evaporation between trees is mainly in the water vapor diffusion stage.The evaporation is difficult to measure,making the synthesis method less accurate after September.The path analysis of the simulated results of intercropping evapotranspiration showed that solar radiation,the lowest temperature and the highest temperature were the main factors affecting crop evapotranspiration.