Journal of Taiwan Agricultural Research

Author:Ming-Hwi Yao*, Shou-Hung Chen and Liang-Sheng Lien

Abstract:

    The concept of radiation-use efficiency (RUE=carbon assimilated per unit intercepted photosynthetic photon flux density) is commonly used for analysis and modeling of crop growth. Field experiment was conducted in 2004 to evaluate RUE as a function of growth and development in paddy field of Agricultural Research Institute. Twenty-minute average of carbon assimilation rate was obtained from Bowen ration/energy balance (BREB) system, and light was measured with quantum sensors or pyranometers. Results indicated a high correlation between CO₂ flux and intercepted light flux during heading stage of rice, and the RUE values of rice ranged from 1.11 to 2.32 gMJ^-1 day^-1 in first crop, and 0.95 to 1.5 gMJ^-1 day^-1 in second crop. The mechanism underlying the higher values of RUE measured in this experiment, relative to those of other studies is not clear. However, the changes in diffuse radiation proportionality may insert a potential influence. Despite of this, we concluded that when RUE is a rice growth model parameter, it may be changed by varied LAI in different growth stages.

Key words:Rice, Radiation use efficiency, Flux

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