The Soil Water-thermal And Water-salt Numerical Simulation In Farmland Under The Implementation Of Water Saving Irrigation Coupled With Tile Drainage In Huinong Irrigation Area

Water saving irrigation and drainage needed to be combined to promote efficient agriculture water management in Yinbei Huinong irrigation district in Ningxia.A combination of field test monitoring and numerical simulation was used to systematically study the water-saving irrigation and subsurface drainage in Huinong Irrigation District Farmland.Farmland water-heat,water-salt transport and their numerical simulation are of great significance to the improvement of saline-alkali land in modern ecological irrigation areas,the efficient use of soil water,fertilizer,gas,heat and crop quality and efficiency.The main research conclusions are as follows:The main research conclusions are as follows:(1)To explore the content and emerging trends of subsurface drainage research at home and aboard.Analyzing literature citation data of subsurface drainage research download from WOS and CNKI database,by adopting scientific text mining visualization software VOSviewer and Citespace.It is concluded that there are 12 active research directions and high-impact research institutions in the field of subsurface drainage,and it reveals the differences in the research content of underdrainage at home and abroad.Cooperation.The analysis shows the future emerging trends in the field of underdrainage research.(2)Through the field water and heat observation experiment of Huinong Irrigation District,the law of water and heat change of farmland soil in water-saving irrigation and subdrainage area was obtained.The law of temperature change in the vertical one-dimensional space followed the Fourier thermal conductivity.The temperature change of the deep layer below 70 cm in the soil is not obvious,because the local groundwater level is high,and the high soil moisture content in the deep layer results in the combined effect of large heat capacity and long temperature penetration distance.The magnitude of the daily variation of soil temperature is very sensitive to the moisture content.The daily evaporation distribution model proposed by Fayer is used to simulate the daily variation of soil surface moisture,and the(PDV)model is used to simulate the daily variation of the hourly accuracy of each layer of soil.The simulation results are consistent with the measured results.(3)The SIMDualKc-HYDRUS farmland hydrology integrated model was used to simulate the farmland soil water conversion process and farmland soil water and salt under different crop growth process conditions.Changes,changes in various field waters(rainfall,irrigation,irrigation water leakage,rise of capillary water to replenish crops,soil evaporation,actual evapotranspiration)and soil water consumption process.During the entire growing period,the deep field leakage reached 30%±2%of the irrigation water,and the underground capillary water supply to the crop water accounted for 25.2%and 22.7%of the actual crop water demand,respectively.The soil salt content in the field during the crop growth period did not change much,and the soil salt reversion was mainly caused by soil evaporation.In the middle and late crops,the leaves matured with a larger canopy,and the soil evaporation was not obvious,so there is no need for this period.Salt washing,so the planting density of the crop and soil cover are important means to solve the problem of soil salt return during the growing period.Irrigation methods using small flow rate and multiple times irrigation method is an effective means to reduce the risk of reducing production.(4)In order to analyze the adaptability and difference of different ETO model at different time steps in Huinong Irrigation District,and to explore the multi-year average sensitivity of each model to five meteorological elements,Taking Huinong Irrigation District as the research object,the ETO value was calculated using the REF-ET calculation reference evapotranspiration software,and the FAO-56 model was used as the benchmark.The statistical indicators RMSD and MAD were used to evaluate the applicability and difference of each model.The sensitivity analysis method of partial derivative is used to analyze the sensitivity analysis of different ETO calculation models to various meteorological elements(temperature,relative humidity,wind speed,sunshine hours).The suitability index RMSD value of each model based on the daily time step is 0.05mm/day?2.34mm/day,and the RMSD value based on the suitability index of the monthly time step is 1.4mm/month?66.4mm/month.The MAD value of the difference index between step and month time step is 1.5mm/month?13.15mm/month.The MAD value of each model is analyzed.The ETO value calculated by each model based on the time step of month and day is not significantly different.ASCE-Penman Monteith,ASCE-STAND,FAO56-PM,1972-Kimberly-Penman,1948,63 Penman FAO-24 PM and FAO-PPP-17 PM models have the highest sensitivity coefficients for relative humidity,1996/82-Kimberly-Penman,FAO Blaney-criddle and 1985 Hargreaves-Samani models have the most sensitive coefficients for the highest temperature,FAO-24 radiation,1972 Priestley-Taylor and Makkink models have the most sensitive coefficients for the hours of sunshine,and the Turc model has the most sensitive coefficients for the lowest temperature.It is concluded that the ASCE series has high adaptability in Huinong area,followed by 1948 Penman and Kimberly-Penman series;Turc and FAO-24 Blaney-Criddle models are not suitable for Huinong area.