Journal of Taiwan Agricultural Research

Author:Chwen-Ming Yang

Abstract:

    This study was to analyze the 2-dimensional infrared thermal images of rice canopy vertical profile taken from rice plants (Oryza sativa L. cv. TNG 67) grown under soil water deficits in the first and the second crops of 1998. Changes of canopy radiant temperatures at 10 different vertical layers in response to soil water potential compared to air and ground radiant temperatures were also investigated. It showed that canopy temperature was affected by environmental conditions and was elevated by soil water deficiency in both crops. Radiant temperatures measured from 10 different layers of canopy vertical profile were all increased with increasing stress magnitude, especially temperature of near-ground layer. Generally canopy temperature was lower than ambient air temperature and ground temperature under well-watered condition yet may surpass them at certain stress levels. Temperature of the near-ground layer would be higher than air temperature when soil water potential (Ψsoil) dropped to -0.25 MPa. When Ψsoil decreased to -0.75 MPa, temperature of the uppermost layer would be greater than air temperature. Near-ground layer temperature surpassed ground temperature at Ψsoil below -0.20 MPa, and uppermost layer temperature would larger than ground temperature at Ψsoil below -1.50 MPa. When Ψsoil was higher than -0.04 MPa, no significant temperature difference was found between layers of vertical profile. When Ψsoil was reduced to less than -0.04 MPa, layer temperature was increased vertically toward the ground. The trend was similar in both crops.

Key words:Remote detection, Rice vertical canopy profile, Radiant temperature, Water deficits, Infrared thermal imagery

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