| The gravel-sand mulched is an agricultural planting technology with a history of more than 300 years.It has excellent characteristics of inhibiting soil water evaporation,increasing rainfall infiltration,improving water use efficiency.Sand-covered soil surface can also inhibit soil salt accumulation and improve soil physical and chemical properties.Spring wheat is one of the main crops planted in gravel-sand mulched area.It is of great significance to study the irrigation system of spring wheat for the efficient production of spring wheat in gravel-sand mulched.Based on HYDRUS-2D software,this paper simulated the process of soil water and salt transport during the growth period of spring wheat in gravel-sand mulched under different irrigation schemes,which provided thretical basis for improving wheat yield in gravel-sand mulched fields.The main conclusions are as follows:(1)Using HYDRUS-2D software to simulate the soil water and salt transport under different conditions of sand-covered and uncovered soils,and verify the reliability of the model.The results showed that:under the sand-covered and uncovered soils conditions,the correlation coefficient between the simulated and measured values of soil water content is0.8986~0.9931,the root mean square error is between 0.0395~0.0835,and the simulated value of salt content is related to the measured value.The coefficient is between 0.9074 and0.9951,and the root mean square error is between 0.5763 and 0.8061.Under the conditions of different planting years,the soil water content correlation coefficient is between 0.911 and0.998,the root mean square error is between 0.035 and 0.108,and the soil salt content correlation coefficient is between 0.865 and 0.911.The error is between 0.146 and 0.129.Therefore,the model built with the HYDRUS-2D software enables accurate and reliable numerical simulation of sand-pressed irrigation.(2)Using HYDRUS software,the irrigation simulation of spring wheat jointing-heading period was carried out,and different irrigation amounts W1,W2,W3(1000,1500,2000m~3/hm~2)and different irrigation frequencies T1,T2,T3(1,2,3 times)soil water and salt transport process were analyzed.The results showed that increasing irrigation volume and irrigation frequency could significantly increase soil volumetric water content,effectively leaching soil salinity and reducing salt accumulation.Under each irrigation treatment,the soil water content of the gravel-sand mulched is higher and more stable than that of the uncovered sand soil.The soil salt content of the gravel-sand mulched in the 10cm soil layer was lower than that of the uncovered soil.The soil surface sand-covering can significantly improve the soil water storage and preservation.The ability to reduce the accumulation of salt is conducive to the growth of spring wheat.(3)Using the method of numerical simulation,the soil water-salt migration process under the four irrigation schemes(2250、2500、3000、3500 m~3/hm~2)of the gravel-sand mulched with different planting years in the whole growth period of spring wheat was studied.The results showed that under different irrigation schemes,the soil water content of each soil layer decreased with the increase of planting years,and the soil salt content decreased first and then increased.When the planting years are the same,the average volumetric water content of soil under each irrigation scheme differs by only 0.4%~0.9%.Therefore,irrigation schemes were not a major contributor to soil volumetric moisture content when planting years were the same.The initial salt content of the new gravel-sand mulched and medium gravel-sand mulched wass relatively low,and the effect of the first to fourth schemes is not much different.It is best to use the scheme 1(2250 m~3/hm~2)for saving water resources irrigation quota.The old gravel-sand mulched has a high salt content.In order to prevent soil salinization and achieve desalination effect,the irrigation quota 4(3500 m~3/hm~2)is the best option. |
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