| Objective:Cotton is a major economic crop in Xinjiang,and its growth and development require a good soil environment.Soil moisture,salinity,and gas are the key factors for building the soil environment of cotton fields.The law of-salt-gas interaction can not only give practical meaning to water-saving and high-yield science and technology in cotton field water-saving mode,but also provide guidance for regional carbon management in farmland.Method:In this paper,the soil moisture,salinity,and co content under different drip irrigation frequencies（T3,T5,T7）,different soil textures（loam and sandy soil）,and different salinity gradients（0.2%,0.4%,0.6%）were studied through barrel experiments.2 concentration change law,analyzes the effect of water and salinity on CO2 concentration.The barrel test can well reveal the water and salt gas regulation of soil profile,and the field test can reflect the surface soil respiration on the soil Response to environmental changes.Monitoring soil cotton respiration and photosynthesis through field experiments,and calculating the carbon changes in cotton soils.Finally,the water-salt-gas under bucket experiments and field experiments were simulated by hydrus model and dndc model.The law of action and the amount of soil carbon change.Under the continuous change of the soil environment,the soil profile and surface soil respiration are combined to jointly reveal the comprehensive mechanism of soil water-salt-gas interaction.Results:（1）Different drip irrigation frequencies have different effects on the water transport of different soil textures.With the decrease of the number of irrigations,the single irrigation amount increases,and the soil layer affected by water disturbance is deepening.Under the T7 irrigation frequency,the soil water before and after irrigation The largest fluctuations,and the deepest impact depth,can reach 40cm for loam and 50cm for sandy soil.From top to bottom,the intensity of a single fluctuation is 10cm>20cm>30cm>40cm>50cm.（2）Different drip irrigation frequencies are basically the same for different soil textures,and the values are different.As the number of irrigations decreases,the amount of single irrigation increases,and the soil affected by salt is deepening.The salt values of different initial salinity changes The degree is:0.6%>0.4%>0.2%.As the initial salt content increases,the degree of salt change will increase.（3）The CO2 concentration in the soil profile has been continuously increasing under the dual influence of soil moisture and soil salinity,and the single fluctuation range is:T7>T5>T3.Single maximum fluctuation of loam soil The degree is 10cm>20cm,and the performance of sandy soil is 10cm>20cm>30cm.The soil CO2 concentration increases continuously with the increase of soil water content,and the single fluctuation value increases before and after irrigation,but when the soil salt exceeds 3.5g/kg,The soil CO2 concentration basically no longer fluctuates,only in an ever-increasing change.（4）The daily change of soil surface respiration rate in cotton fields showed a single-peak curve change,and the peak value appeared around 16:00;the daily change of cotton net photosynthetic rate showed an alternating trend of single and double-peak curves.Each peak appears at about 12:00,the second peak appears at about 16:00,and the peak value of the single peak curve appears at about 14:00.The monthly changes of soil respiration rate and cotton net photosynthetic rate both increase and then decrease.It is the same as the temperature change law.Cotton fields show carbon sinks throughout the cotton growth period,and the total net carbon sequestration is 2203.7 C g/m 2（5）Using the experimental data of the barrel test and field test,using hydrus to simulate soil water and salt transport,and using dndc models to simulate changes in soil CO2 concentration and cotton field carbon change under different irrigation regimes.Comparing the simulation values,it can be found that the simulation accuracy of the models is relatively high.The verified model is used to simulate the carbon change under different irrigation systems in cotton fields,and the results are also very reliable.The combined application of this model is used to study the carbon emissions of farmland areas.And the effects of moisture and salt on it. |
