| There are plenty of light and heat conditions and rich land resources in Northwest China,but water resources are in short supply.The development of water diversion irrigation in these areas is a basic measure to solve the long-term desolation of large ploughed ploughing land and ensure regional agriculture and economic development.For a long time,people have been developing artificial irrigation to develop long-term deserted land resources in arid areas so as to meet the rapid growth of population.However,large area artificial reclamation and extensive farmland irrigation have caused large area of water and salt migration,reorganization and accumulation in the region,and their characteristics are different in different hydrogeological units.In order to prevent the change of regional water and soil environment caused by extensive irrigation,the emphasis of the planning and construction of irrigation and water conservancy projects has shifted from how to enlarge irrigation area and improve irrigation efficiency,how to change irrigation mode,adjust the water use structure in irrigation area,improve agricultural water use efficiency and slow down the degradation of water and soil resources caused by irrigation.In order to avoid the potential hazards of secondary salinization,a rational and scientific irrigation mode and water management measures to control the groundwater level and control irrigation water have been played a key role in alleviating soil salinization in the irrigation area.In view of this,this paper selected the landscape irrigation area as the study area,focusing on the field scale water and salt migration law under two kinds of ground irrigation under border irrigation and furrow irrigation.Through the selection of the typical fields in the irrigation experiment station,the furrow irrigation experiments and border irrigation experiments were carried out respectively.On the basis of the zoning test,the HYDRUS-3D-based gully was constructed respectively.The salt transport model of irrigation and the salt transport model of border irrigation were further simulated in the two irrigation modes of border irrigation and furrow irrigation.The research is based on the influence of water and salt migration on water and soil environment in the dry water irrigation area(Jingdian Irrigation Area)by the National Natural Science Foundation of China(51279064),the study on the effect of field irrigation on the regional soil water salinity in the arid desert area(51579102)and the typical desert plants in the Hexi Corridor The study on the drought resistance structure and its spectral characteristics(31360204)was combined to explore the process of water and salt migration under different irrigation modes through field experiments and numerical simulation,and the following conclusions were drawn:(1)The soil moisture content of the soil under border irrigation and furrow irrigation showed a certain decline trend,and the upper water content was generally less than the lower water content,and the soil water content of border irrigation was slightly higher than that of the furrow irrigation,but the decrease trend of water content was slightly lower than that of the furrow irrigation.In general,the trend of soil moisture content under the two irrigation modes was more than that of the furrow irrigation.For a long time,the soil moisture content of border irrigation is slowly reduced,and the water content is stable to a threshold,which is about 20%,and the threshold of soil moisture content in furrow irrigation mode is 16%.(2)The soil moisture content of the three soil layers is getting smaller and smaller,the average moisture content of border area is about 39%,the water cut in border is about 35%,and the water cut at the end of border is about 33%.That is,the value of soil moisture content is in turn,the soil moisture content is in turn,and the soil moisture content is water in the irrigation period.The main driving force of the change is irrigation infiltration.However,during the non-irrigated period,the main driving force of soil moisture change is evapotranspiration.(3)The salt content of the soil decreased first and then increased under the two irrigation modes.The salt content in the upper soil was generally greater than the salt content in the lower soil,and the soil salt content in each slope showed a certain upward trend on the whole,and the change of soil salt content were all stable,and no large fluctuation of salt content had occurred.(4)For border irrigation,from the first to the border,from the last to the border,the soil salt content of the three soil layers is getting smaller and smaller,the average salt content of the border head is about 4.398 mg/cm3,the border middle is about 4.212 mg/cm3 and the border tail is about 4.086 mg/cm3,that is,the value of the soil salt content is in turn in the border head>border middle>border tail,causing the soil salt content to present this The reason for the law is the coupling of irrigation and infiltration and non-evapotranspiration during irrigation.(5)The salt content of the soil is divided into three regions under the furrow irrigation mode:one area is in the irrigation ditch,the salt content of the soil is low,about 2.5 mg/cm~3,and the two area is in the ditch top planting area.The salt content of the soil is larger,the maximum salt content is above 7mg/cm~3,and the three area is the other part of the simulated single element.This part mainly lies in this part.In the middle and lower layer of the soil column,the salt content of the soil is relatively stable and distributed evenly,and the average salt content is about 3.8mg/cm3.The main factors that cause the change of soil salt content are the coupling effect of irrigation-infiltration and evapotranspiration,and the part of the irrigation ditch,due to the effect of irrigation water,is low in salt content,the planting area of the top of the ditch,the transpiration of crops and the converging area of soil evaporation.Therefore,most of the soil salt is"carried"to this In this part,the salt content of the soil is high and the salt accumulation occurs.In the third parts of the soil,the soil salt content is more stable and more uniform because of the less effect of irrigation and evapotranspiration.The main driving force for the change of the salt content in this part is the mechanical mass scatter.(6)Considering the agricultural development in the northwest of China,in order to achieve the goal of water saving and controlling salt,furrow irrigation can be used as the main irrigation mode in the crop growth period,and border irrigation is used as irrigation mode in the growth period. |
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