Journal of Taiwan Agricultural Research

Author:Ming-Hwi Yao*, Jin-Chuan Tsai and Lien-Sheng Liang

Abstract:

    Vertical profiles of air temperature、light intensity、relative humidity、wind speed and CO₂ concentration were observed within and above a rice canopy in paddy field of Taiwan Agriculture Research Institute. In order to evaluate the reasonable irrigation water requirement in paddy field, the eddy correlation system has been established, not only to detect energy fluctuation, but also to evaluated the energy balance with different soil water condition. The results indicate that the temperature profiles within and above plant canopy exhibited remarkable diurnal variations, the difference of temperature was 2℃. In the daytime, the maximum temperature was observed within the plant canopy. The relative humidity and CO₂ concentration within and above plant canopy were significant different during night period, however, the difference during day time were not significant because the wind increased the air turbulence. The surface energy balance equation was used the closure ratio (the ratio of sum of latent and sensible heat fluxes to the sum of net radiation and soil heat flux) as the evaluated index. In our study the average of closure ratio was 0.85. Bowen ratio (sensible heat / latent heat) was used to evaluated the change of energy component on the soil condition of paddy field, the results showed this ratio will be changed when soil tension was 40 centibar during the maximum tillage stage of rice.

Key words:Micrometeorology, Eddy correlation system, Evapotranspiration, Closure ratio, Bowen ratio

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