Evapotranspiration Characteristics of a Field with Sugar Cane Planted in Summer in Miyako Island, Okinawa Prefecture

概要

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Evapotranspiration (ET) characteristics of a field with sugar cane planted in summer were studied using the Bowen ratio heat balance method. ET was in the range of 0-7.20mm/day with an annual average value of 2.86mm/day. The maximum value of ET was 7.20mm/day on July 7 when incident solar radiation as well as soil moisture was highest. Net radiation received was distributed mainly as latent heat flux, while sensible heat flux and soil heat flux were relatively small. However, the sensible heat flux component increased with the decrease of the soil moisture. When the crop coefficient (AET/RET) for sugar cane over the year was calculated based on the actual ET/reference ET ratio, the use of the FAO PENMAN method and the FAO PENMAN-MONTEITH method was suitable for the peak of a crop coefficient in June, and the values were 0.90 and 1.07, respectively. The crop coefficient calculated by the radiation method was in the range of 0.75-0.93 from January to June. After July, the crop coefficient decreased with the volumetric water content. The typhoons, which occurred several times and the low soil nutrient status may have influenced the growth of sugar cane and the value of the crop coefficient.
日本熱帯農業学会の論文