摘要
摘要:为精确测定、准确模拟阿克苏地区滴灌枣树腾发过程，基于大型称重式蒸渗仪测定枣树全生育期逐时及逐日腾发强度（ET），利用水量平衡方程、PM公式及经典统计原理，分析不同时间尺度下叶面积指数（LAI）、气象因素[温度（I）、风速（V）、净辐射（R_n）]、表层土壤含水率（W）与枣树腾发强度的相关关系并建立预测模型。结果表明：枣树日内腾发强度呈单峰型变化趋势，夜间变化幅度较小且腾发贡献率低。枣树全生育期逐日腾发强度变化呈先增大后减小的趋势，花期的腾发强度最大，为4.42 mm·d^-1；全生育期腾发总量为640.83 mm，其中花期和果实生长发育期耗水量占比较大，分别为38.61%和32.72%。在小时和日时间尺度上，影响腾发强度的主要因素不完全相同，且影响程度有所差异。综合考虑各影响因素，以萌芽期、花期、果实发育期为基础，分别建立以小时、日尺度下估算腾发强度的经验模型ET₁（h）=0.153+0.004T+0.012V+0.176R_n+0.002W+0.067LAI、ET₂（d）=-3.325+0.081T+0.163R_n+0.069W+2.089LAI，拟合度R²均在0.7以上，以果实发育期与成熟期数据对模型进行检验，纳什效率系数分别达0.63、0.80。经偏相关检验，冠层净辐射（R_n）对两种尺度的腾发强度均影响最显著，因此以枣树全生育期数据量为基础，仅建立冠层净辐射（R_n）与腾发强度的回归模型ET₁（h）=-0.063 3R_n²+0.361 2R_n—0.003 7、ET₂（d）=-0.018 3R_n²+0.684 7R_n–1.642 1，R²分别为0.704 7与0.743 6，可满足缺少数据支撑情况下的腾发过程估算。这些模型明确了阿克苏地区滴灌枣树腾发机制及影响程度，可为水分管理精准化提供计算基础。
关键词:腾发强度/
气象因子/
时间尺度/
枣树/
滴灌
Abstract:Measuring field evapotranspiration can provide important information needed for estimating soil moisture and crop water stress and premature drying out, and such information is essential for irrigation formulation. Evapotranspiration can be measured using large lysimeters that have the advantage of confining soil boundaries, flexible measuring intervals, and high precision. Most of studies of evapotranspiration have been done for annual crops such as wheat and maize, and the present study was conducted to measure evapotranspiration of jujubes. Jujube trees of four years were transplanted into lysimeters and evapotranspiration was measured at 30-min intervals for complete growth season. The correlation between evapotranspiration rate and leaf area index, meteorological factors, and surface soil moisture content was analyzed based on water balance and the PM formula. The daily evapotranspiration of jujube was unimodal, taking place mainly in the daytime; the contribution of was small and stable. Evapotranspiration peaked at flowering stage, reaching 4.42 mm·d^-1, and then declined gradually. The total evapotranspiration during growth season was 640.83 mm, a large proportion of which occurred during flowering and fruit development stages that accounted for 38.61% and 32.72%, respectively. The observation suggested that there is a need for flowering and fruit stages to be emphasized in irrigation of jujube trees. Hourly and daily evapotranspiration rates of jujube were different in their affecting factors. The wind speed (V) affected hourly evapotranspiration only. The most sensitive factor for evapotranspiration was canopy net radiation (R_n), followed by air temperature (T), wind speed (V), leaf area index (LAI), and surface soil moisture content (W), as summarized in the following empirical equations for hourly and daily evapotranspiration, respectively:ET₁(h)=0.153 + 0.004T+ 0.012V+0.176R_n+0.002W+ 0.067LAI, and ET₂(d)=-3.325 + 0.081T+0.163R_n + 0.069W+2.089LAI. Because canopy net radiation had the largest and most significant impact (the partial correlation coefficient was 0.562^** and 0.468^** for the hourly and daily equation, respectively), the regression was simplified as ET₁(h)=0.232 6R_n + 0.018, R²=0.719 6, and ET₂(d)=0.321 2R_n-0.141 8, R²=0.719 6. These equations were tested to be accurate and could be used to estimate the evapotranspiration rate of jujube for developing drip irrigation in arid areas when input data were complete or partially complete.
Key words:Evapotranspiration rate/
Meteorological factors/
Time scale/
Jujube/
Drip irrigation



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