Study On Deep Soil Recharge Characteristics And Response For Irrigation Of The Irrigation Farmland In Ulan Buh Desert

The distribution of water resources is not balanced in China.The contradiction between water and land resources is especially prominent in Northwest China.With the increase of population,economic growth,the continuous improvement of the people's living standards and the acceleration of the urbanization process,the agricultural water resources and the management of agricultural water use in the northwest arid area are facing great challenges.The study area is located in Dengkou County on the east edge of the Ulan Buh Desert.The area is located in the upper reaches of the Hetao irrigation area,and the ecological environment is fragile.The irrational use of water resources will cause a series of environmental problems,such as land desertification,groundwater funnel,secondary salinization and so on.How to improve the agricultural water-use-efficiency?WUE?and reduce the loss of agricultural water is important to improve the existing irrigation systems and the sustainable development of the region.The deep soil recharge?DSR?of irrigated farmland is one of the main reasons that affect the efficiency of agricultural water use.Therefore,the systematic analysis of soil moisture and DSR law of different soil types farmland is of great practical significance to the study of farmland ecological hydrological process,guidance of agricultural production and the rational utilization of regional water resources.In this study,three soil types?sandy soil,loam,clay?in Ulan cloth and sand area are replaced by the soil layer below 50cm in the Common Maize Farmland in Dengkou County,East edge of the Ulan cloth and the eastern edge of the desert.Using ECH2O-5 soil moisture sensor,type 105 soil temperature sensor and YWB-01 type soil deep water leakage recorder,real-time,continuous and dynamic monitoring and monitoring of soil volume and water content in soil layer of 0¹50cm soil layer,0⁵cm soil layer soil temperature and150cm in soil soil and clay farmland from January 1,2017 to December 31st are monitored and monitored.The deep leakage of the layer below the layer.Comprehensive analysis of the law of deep seepage in farmland of different soil types;accurately calculate the value of each component in the water balance of farmland through actual monitoring value,and estimate the optimal irrigation water of different soil types from the angle of reducing the loss of water resources leakage.The results and conclusions are drawn as follows:?1?The study is aim to the effects of traditional irrigation methods on soil moisture in the study area.From April 2017 to September corn growing season 5 times irrigation were734.39mm,0¹50cm of different types of farmland soil moisture had significant effect?P<0.01?,the variation degree of different soil types in the farmland affected by irrigation of different layers:Variation degree of soil volume water content in sandy soil,50cm soil layer?59.67%?>5cm soil layer?37.63%?>100cm soil layer?33.56%?>150cm soil layer?12.86%?;The variation of soil volumetric water content in loam soil was 50cm soil layer?34.79%?>5cm soil layer?26.91%?>100cm soil layer?14.45%?>150cm soil layer?12.64%?;The variation of soil volumetric water content in clay farmland is 5cm soil layer?25.33%?>50cm soil layer?24.82%?>100cm soil layer?11.21%?>150cm soil layer?9.67%?.The average volume water contentof0¹50cmsoilindifferentfarmlandtypesissandysoil?30.84%?>loam?19.87%?>clay?16.65%?.?2?During the experiment,there were DSR in different farmland types under 150cm level,and there were obvious differences in DSR characteristics between different soil types.A total of deep leaking water 452mm was produced in sandy soil throughout the year,mainly from April to August,and from April to August,the leakage of 26 days 449.6mm was observed,accounting for 99.47%of the total amount of the year.The amount of leakage during the growth period was as follows:There was a total of deep leaking water 135.8mm in the sowing and jointing period.There was a total of deep leaking water 208.2mm in the jointing and heading stage,and a total of deep leaking water 38.6mm in the heading and filling stage,and a total of deep seepage water67.0mm in the filling period.The characteristics of deep seepage in loam soil generally include daily leakage,slow seepage speed and long total leakage time.A total of deep leaking water177.4mm was produced in the year,and the leakage was concentrated from April to September.The total leakage of 166 days was observed in the 6 months,accounting for 95.26%of the total amount of leakage in the year,which was due to the superposition and delay effect of the deep leaking in the loam soil,so it could not accurately estimate the DSR in each period of growth.In clay farmland,a total of deep seepage water 5.4mm was produced throughout the year,and the leakage was evenly distributed,and the leakage was stable to 0.2mm every day.The leakage rate was not affected by irrigation or precipitation,which was very different from the farmland and loam farmland.?3?This study can accurately calculate each component value of farmland water balance through actual monitoring.The amount of evapotranspiration(ET_sandy)of each growth period can be estimated by using the I,the deep leakage?DSRsandy?and the precipitation?P?during the growth period,and the difference of the average amount of water in each growth period(?W_sandy).The order of evapotranspiration in each growth period of sandy soil is:Grain filling date?126.32mm?,sowing to jointing stage?118.21mm?,jointing heading date?85.25mm?and heading filling stage?53.37mm?.However,the average evapotranspiration of each growth period should be divided by the number of days,and the average daily evapotranspiration in the growing season is 2.16mm·d^-1,as the duration of each growth period is different.The order of daily evapotranspiration in each growth period is:Heading to grain filling stage(2.54mm·d^-1),jointing heading date(2.51mm·d^-1),grain filling period(2.34mm·d^-1),seeding and jointing stage(1.64mm·d^-1).The daily leakage of loam farmland is small and the leakage has long duration,which causes the DSR of the loam with time delay and superposition effect,and can not accurately calculate the DSR of each growth period.Therefore,the loam farmland uses total irrigation amount?I?,the total amount of DSR of the whole growth period(DSR_loam),the difference value of the total growth period of the growth period??Wloam?.The evapotranspiration(ET_soil)of loam soil during the whole growth period was estimated.The total evapotranspiration of loam soil in the whole growth period is 294.18mm,and the average daily evapotranspiration is 1.61mm·d^-1.?4?From the perspective of minimizing the DSR of water resources,we can estimate the optimal irrigation volume of farmland with different soil types.The optimal irrigation amount for each growth period of sandy soil is:The optimum irrigation amount for sowing and jointing period should be 75.7mm;the optimum irrigation amount of the jointing and heading stage should be 95.26mm;the optimum irrigation amount in the heading and filling period should be31.73mm;the optimum irrigation amount in the grain filling period should be 55.1mm.The optimal irrigation amount in the whole growth period was 257.79mm.At the same time,we can cooperate with a small number of irrigation measures during the growth period to reduce water loss.The optimal irrigation amount in the loam farmland to minimize the loss of water leakage is a total of 538.39mm during the whole growth period.In the clay farmland,the deep seepage loss of irrigation is not considered temporarily,and the irrigation volume only needs to meet the optimal crop yield.However,the related issues are not clear yet.Further research is needed.