Abstract
Rice plants (Oryza sativa L. cv. TNG 67) were grown in the second cropping season of 2002 and the first cropping season of 2003 and infrared thermograms were taken by a thermal infrared imaging system. In Taiwan, air temperature, irradiance, and sunshine hour generally increased from lower to higher values following plant development in the First Crop, and vice-versa in the Second Crop. Canopy radiant temperature corresponded to changes of ambient air temperature during the growing periods and this cause-effect relationship affected the trend of temperature differences between ambient air and canopy as plants developed. However, such temperature differences were decreased by the increasing of air temperature in the First Crop and were decreased by the decreasing of air temperature in the Second Crop. There was a tendency that temperature difference increased with the increasing rates of nitrogen fertilizer in both crops, yet no such clear gradient was found near harvest. When further analyzing temperature difference distributions of rice plants treated with different rates of nitrogen, results indicated that, except near harvest, plants treated with higher nitrogen rates generally showed higher levels of temperature difference distribution and the phenomenon may be used as an indication of plant nitrogen status assessment in the first place.
