Estimating soil surface evaporation from fields irrigated by micro systems

评价灌溉水消耗利用效率。将土壤表面蒸发分量与蒸腾分量分开估算是有意义的。当田地被微灌系统灌溉时。在土壤表面形成湿润区。估算湿润点的蒸发率对于量化灌溉用水量非常重要。首先。对土壤表面二元层中的蒸汽扩散机理进行了实验研究。用薄石膏层制成的蒸发计，观察到能给出较好的估计。中学。探讨了土壤表层水分扩散的机理。利用土壤水势测定装置，观测了土壤干燥降速阶段表层土壤体积含水量的分布。用此观测值确定的水流量与总和模型的计算结果进行了比较。用这种技术，水在表面层中的扩散率进行了精确的研究。

To evaluate the consumptive use efficiency of irrigated water. it is interest to estimate the soil surface evaporation component separately from transpiration component. When the fields are irrigated by microirrigation systems. wetted area are formed on the soil surface. Estimating evaporation rate from the wetted spots are important to quantify the water for irrigation.Two approaches were pursued on this project. Firstly. vapor diffusion mechanism in the binary layer on the soil surface was experimentally examined. Evaporimeter made with thin plaster layer was observed to give good estimation. Secondary. the mechanism of water diffusion in the the vicinity of soil surface was examined. Using an equipment to measure soil water potential, distribution of volumetric soil water contents during the fallen rate stage of drying in the surface layer were observed. Water flow rates determined with this observation were compared with calculated results of summation model. With this technique, water diffusivity in the surface layer were precisely investigated.