华北冬小麦-夏玉米农田水分动态模拟研究

冬小麦-夏玉米连作是华北地区主要的粮食作物种植模式。根据华北季节性冻土区的特点,将全年划分为作物生长期与越冬期,分别建立了作物生长条件下农田水分运移模型、冻融条件下土壤水热运移模型。前一模型主要包括参照腾发量计算、腾发量分配、作物根系吸水、土壤表面蒸发、土壤水分特征参数和土壤水分运动等子模型;后一模型主要包括冻土水热耦舍迁移、地气水热交换等子模型。应用以上模型对冬小麦-夏玉米连作条件下的土壤水分过程进行模拟,根据北京永乐店试验资料对模型进行检验。模拟了不同降水水平年、不同灌溉处理下的农田灌溉制度及土壤水分过程,分析了降水、灌溉对农田蒸散、土壤水利用、深层渗漏等的影响。

Simulation of Water Cycling in Wheat-maize Field in North China

The double cropping of winter wheat and summer maize is the major schema in the North China Plain. As the seasonal freezing in this region, a cropping year is divided into two periods, i. e. , crop growing period and frozen period. The model of soil water movement for crop growing period and the model of soil moisture and heat transfer (SMHT) for the frozen period were established repectively. The former was based on Richards equation of soil water movement with sink term and composed of soil hydraulic properties, reference vapotranspiration , soil surface evaporation and crop transpiration allocation and root water-uptake models. An implicit mass-conserving finite volume method (FVM) procedure was used to solve the model. The SMHT model was adopted for soil water movement in winter, and a model of water and heat exchange between soil and atmosphere in freezing and thawing period was used to estimates the upper boundary conditions for SMHT model. The models were calibrated with the data from of the Yongledian experimental station near Beijing. The field water status under different precipitation and irrigation schedules were simulated. The impacts of precipitation and irrigation on field evapotranspiration, soil water use and deep seepage were analyzed based on the simulation results.