Characteristics And Simulation Of Soil Water Transport In Typical Red Soil Sloping Fields In Southern China

As an important agricultural production area in China,the red soil area is affected by the monsoon climate and has problems such as soil erosion,seasonal drought,and poor ability to retain water and fertilizer,which poses a serious threat to the safety of China’s grain and oil production.As the link connecting the various hydrological elements of the slope,soil water is deeply involved in various hydrological processes.Therefore,revealing the law of soil water migration is helpful to the safety of China’s agricultural industry.To explore the characteristics of soil water movement on the sloping land of red soil in southern China,this study uses a combination of field in-situ monitoring,laboratory experiments,and numerical simulations,using soil moisture data and meteorological rainfall from May 8,2018 to May 7,2019.Data and soil characteristic parameters.Firstly,the influence of rainfall and slope position on soil moisture in red soil slopes at different depths is deeply explored.Secondly,the temporal and spatial distribution characteristics of water storage in different growth periods of crops are clarified.The soil water transport model in the unsaturated zone of red soil sloping land,and finally revealed the response process of the law of soil water transport to soil texture,crop potential evaporation,and rainfall through the method of scenario simulation,aiming to provide theoretical support for agricultural production and water conservancy irrigation And government decision-making services to realize the sustainable development of the local agricultural economy.The main research results of the thesis are as follows:(1)The soil moisture in the study area increased with the increase of soil layer depth;in the process of response to rainfall,the soil moisture response at 20 cm and 40 cm is relatively rapid,there is a hysteresis phenomenon at 130 cm,and the response at 230 cm is weak.The difference of soil moisture on slope position is not obvious,and the coefficient of variation of soil moisture decreases spatially with the increase of soil depth.(2)According to crop planting planning,the study period is divided into peanut growth and development period,soil fallow period,and rape growth and development period.During the growth and development period of peanuts and the fallow period,the soil moisture is in the depletion period.Peanuts will be affected by long-term drought and water shortage during the pod-setting period and the full-fruit mature period(July and August);the soil moisture in the growth and development period of rape is in the accumulation period.In the early stage of seedling(September and October),soil water storage is low,and rape seedlings will be affected by drought.(3)Based on the HYDRUS-1D software to build the soil moisture transport model of the southern red soil sloping land,the error analysis found that the simulated value is similar to the measured value,and the accuracy of the deep soil moisture simulation value is better than that of the surface layer.Therefore,the accuracy of the model is relatively high,and it can show the law of soil water movement in the southern red soil sloping land more realistically.(4)Application of scenario simulation method to explore the influence of soil texture,crop potential evaporation,and rainfall on soil water movement.The simulation shows that the amount of soil excretion at the lower boundary of an aerated zone is related to the soil sand content,and the amount of soil excretion at the lower boundary of the aeration zone decreases with the decrease of the sand content;during the simulation period,the amount of soil moisture change varies with the potential evaporation or rainfall of the simulated crop.It increases as it rises,and the change is greatest at a soil depth of 40 cm.