The Threshold Value of Solar Radiation on the Evapotranspiration Models in Subtropical Greenhouses

亞熱帶溫室蒸發散模式的太陽光能量臨界值

陳令錫(Ling-Hsi Chen) ； 陳俊源(Jiunyuan Chen) ； 陳加忠(Chiachung Chen)

《農林學報》 68卷4期 (2021/12) Pp. 217-229

https://doi.org/10.30089/JAF.202112_68(4).0002

摘要

Evapotranspiration is a physiological response of plants to the environment. Many greenhouse microclimate models include this evapotranspiration (ET) model to consider some physiological activities such as leaf temperature, stomata opening and closing index, and irrigation control. Evapotranspiration affects the main processes of leaf temperature, crop water demand and greenhouse microclimate. The climate influencing factors involved include solar radiation, temperature, relative humidity and wind speed. However, the solar radiation energy accounts for most of crop evapotranspiration in the high solar radiation conditions. In this study, a simple ET models for tomatoes (Solanum Lycopericum L. Lycopersicon esculentum, Mill.) in a subtropical greenhouse was proposed to observe the threshold value of solar radiation on the ET. The significant effects of these factors were evaluated via the statistical regression theories. The significant factors affecting ET values were found as the solar radiation, vapor pressure deficit and wind velocity. Moreover, solar radiation is the dominating factor as the radiation is ＞ 250 W/m^2 condition, followed by vapor pressure deficit and wind velocity. More than 80% of tomato evapotranspiration in subtropical greenhouses could be explained by variable of solar radiation. The threshold value of solar radiation on the evapotranspiration models is 250 W/m^2. The result provides a simple way to control the irrigation works by the measurement of solar radiation.

關鍵字

Validation ； evapotranspiration model ； regression ； sensors ； threshold value

並列摘要

蒸發散作用是植物對環境的生理反應。許多溫室微氣候模型都包含這種蒸散模式，以考慮葉溫、氣孔開閉指數、灌溉控制等生理活動。蒸發散作用主要影響葉溫、作物需水量和溫室微氣候。所涉及的影響因素包括太陽輻射量、溫度、相對濕度和風速。然而在高太陽輻射量條件下，太陽輻射能量的影響佔作物蒸發散量的大部分。在這項研究中，提出了一個簡單的亞熱帶溫室番茄蒸發散作用模式來觀察太陽輻射量對模式的臨界值。通過統計迴歸理論評估這些因素的顯著影響。結果顯示影響蒸發散作用的重要因素是太陽輻射量、蒸氣壓差和風速。太陽輻射量是主要因素，其次是蒸氣壓不足和風速。在輻射量大於250 W/m2條件下，亞熱帶溫室番茄80%以上的蒸發散率可以使用太陽輻射變量加以解釋。即蒸發散模式的太陽輻射量臨界值為250 W/m2。此研究結果提出了一種以太陽輻射量測值控制灌溉工程的簡易方法。

並列關鍵字

驗證 ； 蒸發散作用模式 ； 迴歸 ； 感測器 ； 臨界值