第二章 作物需水量和灌溉用水量VIP免费

第二章作物需水量和灌溉用水量（CropWaterRequirementandIrrigationWaterUse)第一节作物需水量第二节灌溉制度第三节灌溉用水量第四节灌水率第一节作物需水量一、基本概念二、研究作物需水量的意义三、作物需水量的推求方法一、基本概念1、作物需水量2、田间耗水量1、作物需水量（Cropwaterrequirement）植株蒸腾Traspiration株间蒸发EvaporationTheevapotranspirationofacropisthetotalamountofsoilwaterusedfortranspirationbytheplantsandevaporationfromthesurroundingsoilsurface.Theevapotranspirationiscommonlyexpressedinmillimetresofwaterusedperday(mm/day)作物需水量=植株蒸腾+株间蒸发=腾发量Evapotranspiration(ET)作物根系从土壤中吸入体内，通过叶片的气孔扩散到大气中去的水分referstothemovementofwaterfromthesoilintoaplant,uptheplantbody,andouttheplant’sleavesintotheatmosphere.蒸腾（Transpiration）蒸腾（Transpiration）Transpirationtakesplacesoquickly,thatinarainforest,waterthatisinthesoilinthemorningtravelsinto,up,andoutofatreeintimetobecomerainintheafternoon.(Thishaspromptedbiologiststosaythat“rainforestsmaketheirownrain.”)蒸腾（Transpiration）植株间土壤或田面蒸发的水分referstothemovementofwaterfromthesoilsurfaceorwatersurfaceinpaddyfieldintotheatmosphereevaporationfromthesoilsurfaceisatmostequalbutusuallyconsiderablylessthanevaporationfromanopenwatersurface蒸发（Evaporation）2、田间耗水量（ConsumptiveUseofWater）稻田耗水量=作物需水量+田间渗漏水稻田的渗漏PercolationinpaddyfieldPercolation旱地耗水量=作物需水量影响作物需水量的因素FactorsAffectingCropWaterRequirementFactorEffectoncropevapotranspirationhighlowClimatehotcooldrywetwindynowindnocloudscloudySoilmoisturemoistdrywideplantspacingCropmid/lateseasoninitialorripeningdenseplantspacing气象因素（Climaticfactors）Radiation:suppliesenergytoevaporatewaterfromliquidtovaporAirtemperature:determineshowmuchwateraircanholdHumidity:howmuchwaterisintheairWind:howeasilyamoleculemovesintotheatmosphereDesignnewirrigationsystems二、研究作物需水量的意义schedule(operate)existingones–Directmeasurement(Lysimeters)三、作物需水量的确定DeterminingEvapotranspiration–Calculated(equations)1、作物需水量的观测MeasurementofEvapotranspirationLysimeterMeasuringCropETInsideviewofweighinglysimeter3m1995SoybeanCrop2、作物需水量的计算CalculationofET直接计算需水量通过计算参照作物需水量来计算实际作物需水量直接计算作物需水量的方法以水面蒸发为参数的需水系数法）以产量为参数的需水系数法从影响作物需水量的主要因子（水面蒸发、气温、湿度、日照、辐射等）中选择单因子或多因子，通过实测数据的相关分析，建立经验公式直接计算作物需水量的方法以水面蒸发为参数的需水系数法0EETbEET0PanEvaporationMethod某时段内的作物需水量（mm）与ET同时段的水面蒸发量国内外都有较多应用，我国尤其在水稻地区应用较多Etp=Epan*Panfactor(0.8)*CropfactorEpan=ClassApanevaporation.Thisdataisinterpolatedforeachlocationbasedondatafrommajorregionalcentres.Panfactor=Evaporationofwaterfromapanisaffectedbythepan’sdimensions,windspeed,humidityandthetypeofcropwithintheupwindfetch.Thepanfactoristypically0.8butmayrangefrom0.45to0.85.CropFactor=Empiricalratiosofcroptopanevaporation.Itsvalueisindicativeofthegreenleafareaofthevegetation.直接计算作物需水量的方法以产量为参数的需水系数法KYETcKYETn作物全生育期内总需水量（m3/亩）需水系数作物单位面积产量（kg/亩）我国过去旱作地区应用较多，目前仍有少量应用阶段作物需水量ETKETii1001某一生育阶段的作物需水量模比系数通过计算参照作物需水量来计算实际作物需水量参照作物需水量Refere...