Study On Salt Accumulation And Crop Growth Simulation Of Drip Irrigation Cotton Field Under Different Salinity Water Source Film

Object:brackish water and saline water irrigation is one of the important ways to alleviate the shortage of agricultural fresh water resources in the arid area of northwest China,but brackish water and saline water irrigation make the soil ventilation and water permeability become worse,it is easy to solidify and the pH increases,the reduction of soil microbial population and enzyme activity led to a decrease in crop yield.Methods:in order to analyze the effects of saline water and brackish water irrigation on soil salt microenvironment and cotton physiological growth,six salinity treatments,1g/L（CK）;2g/L（A）;3g/L（B）;4g/L（C）;5g/L（D）and 6g/L（E）,the effects of drip irrigation under mulch with different salinity water sources on soil water and salt,soil salt accumulation,soil pH,cotton physiological growth index and cotton yield were analyzed,Aqua Crop crop growth model was constructed to simulate the cotton growth process.Results:the results showed that the suitable irrigation water source for cotton was between 3～4 g/L,and the optimum irrigation water source for cotton was between 3～4 g/L,Aqua Crop crop growth model can well simulate the growth and development of cotton under drip irrigation with different salinity water sources,and can be used for yield prediction and optimal management of agricultural water resources.Conclusion:（1）the soil moisture content of 0～100 cm soil layer fluctuated with the irrigation date,the change of soil moisture content of 0～20 cm soil layer was affected by the external factors,and the soil moisture content of 40～100cm soil layer was higher than that of other soil layers,the distribution of soil moisture increased first and then decreased,and the soil moisture was enriched in 40～80 cm soil layer.The soil salt accumulation reached the peak at 40～60 cm soil layer.After 12 hours of irrigation,the salt accumulation was most obvious at 20～40 cm wide row surface layer and at 40-60 cm narrow row layer,the average soil electrical conductivity of 0-100 cm increased linearly at the rate of 0.920 ds·m^-1 and 0.995ds·m^-1、1.196 ds·m^-1、1.188 ds·m^-1 per year.（2）saltwater irrigation with different salinity had different effects on soil microbial community diversity.There were significant differences in four soil microbial diversity indices:Simpson index（D）,Chao Index,Shannon Index and Obeserved-species index.Under CK and E treatments,the soil microbial diversity index fluctuated sharply during the whole growth period,and the enzyme activity decreased significantly with the increase of water salinity.At the end of boll-opening period,the change trend of soil Nitrate reductase（NAR）was not obvious.The activity of soil urease was the highest under 5 g/L treatment,and the activity of soil nitrite reductase（NO-forming）（NIR）was the highest under 3 g/L treatment,it reaches the maximum value at the flowering and Boll stage.The pH value of soil fluctuated from 8.03 to 8.48,and the soil was slightly alkaline.There was no significant difference between the pH value of soil irrigated with high-salinity water and that irrigated with low-salinity water.（3）when the salinity of irrigation water was 3～4 g/L,the growth index and yield of cotton were better than other treatments,the effect on photosynthesis index of cotton leaf was the least,and the growth index and yield reached the maximum,the salinity of irrigation water source is 4 g/L and 1 g/L,which has little effect on the growth index and yield of cotton,the suitable irrigation water source for cotton is 3～4g/L.（4）the Aqua Crop crop growth model was used to simulate the canopy coverage,aboveground dry matter mass and cotton yield of drip-irrigated cotton under mulch with different salinity water source.The decision coefficient between the simulated and measured values was greater than or equal to 0.812,the standard root mean square error is not more than 24.1,and the consistency index is not less than 0.984.The simulation effect is good.The relative error between simulated and measured cotton yield was less than 9.28%.Aqua Crop crop growth model can well simulate the growth process of cotton under drip irrigation with different salinity water sources,and can be used for cotton yield prediction and agricultural water resources optimal management.