春玉米生长中期灌水量差异对其蒸发蒸腾量估算精度的影响

为提高旱区作物蒸发蒸腾量估算精度,以石羊河流域春玉米为研究对象,分析灌水量对FAO-56估算作物蒸发蒸腾量精度的影响,并对估算误差进行讨论,提出使用部分根区含水量平均值用于土壤水分胁迫系数计算.结果表明:FAO-56对不同灌水处理下作物蒸发蒸腾量的估算精度存在较大差异,可较精确地估算低灌水处理下作物蒸发蒸腾量;随着灌水量增大,其估算精度有所降低,对高灌水处理下作物蒸发蒸腾量的估算误差达-14.13%;根区上部土层含水量与土壤水分胁迫状况关系紧密,以缓变层及以上土层含水量平均值代替整个根区含水量平均值用于土壤水分胁迫系数计算,可有效改善高灌水处理下旱区作物蒸发蒸腾量计算精度,亦可较为精确地估算低灌水处理下作物蒸发蒸腾量.

Effect of irrigation quota on estimation accuracy of evapotranspiration in growth middle stage of spring maize

In order to improve estimation accuracy of evapotranspiration(ET)of crops in arid areas, the ET of spring maize in Shiyang River Basin in growth middle stage was estimated with FAO-56 in the paper. The effect of irrigation quota on estimation accuracy of ET was identified by comparing calculated values with measured ones. The estimation error was discussed by analyzing the spatial distribution of soil moisture and its change rule under different irrigation treatments. It was proposed that the average water moisture in the entire root zone rather than in the partial root zone should be used in the calculation of soil water stress coefficient. The results show that the FAO-56 can estimate ET accurately under low irrigation quota treatment, however, its estimation accuracy decreass with increasing irrigation quota. As a result, the estimation error in ET is as poor as -14.13% under high irrigation quota. The soil water stress coefficient is calculated with the average soil moisture in the soil moisture slowly changing layer and above. This method can improve estimation accuracy of ET of crops in arid areas under high irrigation quota treatment effectively. 