农田水分循环中的蒸发蒸腾计算

Estimation of evaporation andtranspiration of farmlandwater cycling

用数学模型定量化研究农田水分转化规律是农业节水机理研究的重要方面，但农田水分循环数学模型中的棵间土面蒸发和作物蒸腾过程难于计算。文中通过田间试验总结的土面蒸发和作物蒸腾计算模式，首先用Ｐｅｎｍａｎ公式计算出潜在腾发量，根据作物系数和作物覆盖度划分出作物颗间蒸发和作物蒸腾，再用试验资料总结的棵间蒸发与表土含水率经验关系计算实际棵间土面蒸发。该模式应用于数学模拟计算，其结果与田间实测资料对比，符合实际。文中蒸发蒸腾计算模式在农业节水机理研究中有实用价值。

The quantitative study of farmland water transfer using mathematical model is an important research aspect of agriculture water saving mechanism. But it is difficult to separately calculate the process of soil surface evaporation and crop transpiration in mathematical modeling of farmland water cycling. Based on the field experimental work, the calculation model of soil surface evaporation and crop transpiration has been summarized, using obtained Penman's potential evapotranspiration. The evaporation and crop transpiration can be separated according to crop coefficient and crop coverage ratio in field. From the experimental relation between field soil surface evaporation and soil moisture on the surface, the actual soil surface evaporation could be determined. The model has been applied to mathematical simulation of farmland water cycling and the results seemed good, compared with field observed data. The presented calculation model for evaporation and transpiration has practical value in agricultural water saving study.