FAO56计算水分胁迫系数的方法在田间水量平衡分析中的应用

Application of water stress coefficient from FAO56 to the field water balance analysis

从作物水分胁迫系数的基本概念和FAO56的相关公式出发，考虑土壤临界含水量的时间变化，推导出了一个水分胁迫系数计算公式，该公式比较全面地表达了土壤供水能力、作物潜在腾发量与作物所受水分胁迫之间的关系。将该公式和另一幂函数公式应用于山西潇河冬小麦田间水量平衡分析，两者对土壤水分的动态模拟都达到了较高的精度，水量平衡计算结果也比较合理，模型的参数基本一致。与幂函数公式建立的模型相比，新公式建立的田间水量平衡模型具有待定参数少、求解结果稳定、易于收敛的优点，同时还能得到0～1m土壤临界含水量变化曲线。该曲线反映了作物在土壤水分消退的过程中遭受不同程度水分胁迫的可能性大小，并得出土壤临界含水量在冬小麦生长前期较小，中期最大，后期较大。在返青～收获期，0～1m深土壤临界含水量最大为290mm，最小为215mm，平均值为247mm。这些结论对于农业用水管理具有一定的参考价值。

According to the fundamental concept of crop water stress coefficient and some related equations in FAO56, a new formula computing crop water stress coefficient was deduced considered the temporal change of critical soil water content. This formula can fully express the effects of soil water availability and crop potential evapotranspiration on crop water stress. This formula and another power function formula were applied synchronously to field water balance analysis of Xiaohe Irrigation Station, Shanxi Province. Both of them can simulate the variation of soil water content fairly well and acquire good soil water balance results. And the calibrated parameters from the two models are nearly the same. Compared with the power function formula model, parameters of FAO model are less and can be obtained more easily through optimization. Especially, the FAO model can obtain the fluctuation curve of the critical soil water content which reflects the probability of crop water stress during the process of soil water depletion. The critical soil water is low at the initial growing stage of winter wheat, very high at the middle stage and moderate at the end stage. From greeningharvest stage, the maximum value of the critical soil water content of 0～1 m layer is 29S mm, the minimum value is 215 mm and the average value is 247 mm. This curve can serve as a reference to agricultural water management.