【作者】 王玉宝；

【导师】 王民； 汪志农；

【作者基本信息】 西北农林科技大学 ， 农业水土工程， 2003， 硕士

【摘要】 现有作物需水量的测定方法及计算方法，或测定仪器昂贵、维护困难、计算公式复杂，或所需参数过多且难以获取，不易为我国普遍存在的经济与文化水平不高的农民用户所接受，在实际生产应用中受到很大限制。本文根据土壤的蒸发机制与植物的蒸腾机理，按照参考作物蒸发蒸腾量（ET0）的定义，利用生物膜技术，研制了一种参考作物蒸发蒸腾量的测定仪器，该仪器能很好的模拟稳定蒸发阶段的土壤蒸发与充分供水时植物蒸腾的物理过程。该仪器为植物蒸腾的物理仿真模型。仪器内的水经由进水孔段，进入导管内的填充料，通过毛管力的作用，上升到填充料的上表面。这一输送过程相当于水分由土壤经植物根、茎、输送到叶片的过程。其后，水分子首先在生物膜与填充料的空隙间蒸发为水蒸汽，然后，水分子再通过生物膜的孔隙扩散到大气中。这一过程模拟了叶面气孔中蒸腾的两步，即首先是水分在细胞间隙及气孔下室周围叶肉细胞表面上蒸腾成水蒸汽，然后水蒸汽分子通过气孔下室及气孔扩散到叶外。仪器根据土壤蒸发与植物蒸腾机理进行设计，可模拟稳定蒸发阶段的土壤蒸发与充分供水时植物蒸腾的物理过程。而仪器能够测定参考作物蒸发蒸腾量，在于仪器内的水可借助填充料的毛管力作用上升至填充料表层，持续充分地供给蒸发，其蒸发强度仅决定于气象条件（这相当于土壤蒸发的第一阶段，即稳定蒸发阶段），而与仪器内的水位无关，这符合参考作物蒸发蒸腾量的定义，即充分供水，只与气象条件有关。因此，仪器内的水位变化与参考作物蒸发蒸腾量呈线性关系，可根据仪器内的水位变化直接计算出参考作物蒸发蒸腾量。针对冬小麦和夏玉米两种作物，对仪器的性能进行了田间试验验证。仪器的试验结果采用两种方法进行分析，第一种方法采用比值曲线方法，即将每日仪器水位变化值与参考作物蒸发蒸腾量（ET0）值相比，按日序列研究其变化；第二种方法采用累积曲线方法，即将仪器水位变化值与参考作物蒸发蒸腾量（ET0）值逐日累加，研究二者之间的相关性。比值曲线可很好地证明仪器的水位变化与仪器的水位高低无关；累积曲线能证明仪器的水位变化与ET0有着很好的线性关系（简单的倍数关系），相关系数R值均接近于1。最后对仪器在生产实践中的应用进行了分析，认为该仪器可指导用户进行适时适量灌溉，能满足灌溉预报的精度要求。该仪器使用方便、维护简单、价格低廉、精度较高，具有良好的商品化开发及广阔的市场应用前景。更多还原

【Abstract】 The present measuring and computing methods of crop water requirements have lots of defects when were applied to Chinese peasants, such as a high cost of instruments, a trouble maintenance, a complicate calculating formula, or required parameters are plethora and difficult acquirement. Therefore, it is difficult in applying to agricultural irrigation for the peasants in China who are generally at a low level of economy and culture. A simple instrument for measuring crop evapotranspiration is developed by the technology of biological membrane, according to the definition of reference crop evapotranspiration(ET0), the evaporation mechanism of soil and the transpiration mechanism of plant. The instrument can simulate the physical procedure of soil evaporation and plant transpiration when the moisture in soil is adequate.The instrument is a physical simulating model of vegetation transpiration. The water in the instrument enter the stuff in the vessel through the ports in the vessel, then uplift to the surface of the stuff by the capillary force. This delivery process simulates moisture from soil to leaves through roots, stems. Then the moisture of the stuff surface evaporate into the space between the stuff and biological membrane, disperse to the atmosphere subsequently through the pores in the film. This delivery process simulates the transpiration of air pores in the leaves. That is moisture turn into vapour on the surface of diachyma cells around substomatic chambers or in the intercellular space, and then diffuse to the atmosphere through substomatic chambers and air holes.The instrument is developed according to the evaporation mechanism of soil and the transpiration mechanism of plant, and so it can simulate the physical procedure of soil evaporation of stable phase and plant transpiration supplied water adequately. The instrument can measure reference crop evapotranspiration for the water in instrument goes up to the surface of the stuff by the capillary force to supply evaporate last and fully. The evaporation intensity of the instrument is determined only by the meteorological conditions, and it is indifferent to the water level of the instrument. Therefore, the principle of the instrument conforms to the definition of reference crop evapotranspiration, that is water <WP=5>feed sufficiently and evapotranspiration intensity is relative only to the meteorological conditions. The relationship between the variation of water level and ET0 is linear, so the ET0 could be computed directly by the variation of water level.Field tests ware executed to verify the performances of the instrument at the period of winter wheat and summer corn. The testing data were analysed by two methods. The first is specific value flexure method, that is the quotient of the water table variation and ET0 was studied by day serial. The second method is accumulating flexure method, that is daily water table variation and ET0 were added day by day, and then the relationship between the two cumulative values was studied. The specific value flexures certify that the water table variation in the instrument is indifferent to its water table. The accumulating flexures testify that the relationship between the variation of water level and ET0 is linear, which is simple multiple relation. The relative coefficients are close to one. The instrument applied in practice proofed that the instrument can guide peasants when and how much to irrigate. The precision of the instrument can satisfy the requirement of irrigation prediction.The instrument can be operated and maintained simply. Peasants can afford to buy the instrument easily. Therefore, The instrument will have some prospect in market place.更多还原