Crop Coefficients of Soybean Evapotranspiration in Taiwan

Field experiments were conducted at the Hsueh-Chia Experiment Station for spring seasons of 1993-1995 in Taiwan. Crop coefficients and evapotranspiration of soybean (Glycine max. (L.) Merr.) were estimated for the three seasons. Actual evapotranspiration (ET_a) of soybean was measured in drainage lysimeter, the size is 3 m× 5 m × 2 m. The weather station was set up in the experimental area, daily climatic data were observed. For the computed reference grass ET base, The estimated mean crop coefficients of soybean are 0.47, 0.92, 0.93 and 0.61 in the initial, crop development, mid-season and late season stages in growing season, respectively. The total ET_0 of soybean is about 270.6 to 308.2 mm. Seasonal actual ET varied from 212.2 to 254.4 mm in three growing seasons. The relationships between the mean crop coefficient against the days after crop planting and the fraction of the growing season have been analyzed. These data could be useful to determine crop water requirement quickly in Taiwan.

關鍵字

Soybean ； Crop coefficients ； Evapotranspiration ； Drainage lysimeter ； Penman-Monteith equation

並列摘要

本文乃利用嘉南農田水利會學甲試驗站於民國82至84期間，進行之大豆需水量試驗來探討在台灣地區大豆生長階段之作物係數及其蒸發散量之變化情形。大豆之實際蒸發散量是利用3m×5m×2m大小之排水式滲透計，以定期測定根深土層之土壤水分，配合降雨量、滲漏量與排出水量資料估算之。大豆生長期間之潛在或最大蒸發散量是利用Penman-Monteith公式，配合設置於滲透計附近之氣象站所收集之氣象資料計算之，作物之實際蒸發散量和潛在蒸發散量之比值即可得到該作物之作物係數。經過三年三期作的試驗觀測，大豆生長期間之作物係數，於初期、發芽成長階段、中期階段及成熟收穫階段分別為0.47、0.92、0.93及0.61。大豆生長期間整個期作之潛在蒸發散量範圍是從270.6至308.2 mm而實際蒸發散量則由212.2至254.4 mm。大豆生長期間之作物係數變化，是利用多項式迴歸繪成一作物係數曲線，以分析作物係數與生長天數之關係。本文之目的，即希望將目前在各種氣候狀況下，估算作物蒸發散量最為精確之Penman-Monteith公式，引用於台灣之氣候環境之下，而所得到的結果，企望能對台灣之水資源系統之規劃與設計，及旱作灌溉之營運管理，有所助益。

並列關鍵字

大豆；作物係數；蒸發散量；排水式滲透計； Penman-Monteith公式

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