Wind speed affects drought stress monitoring in mango and longan by thermal photography
- Publikations-Art
- Kongressbeitrag
- Autoren
- Spreer W; Wiriya-Alongkorn W; Spohrer K; Ongprasert S; Müller J
- Erscheinungsjahr
- 2009
- Veröffentlicht in
- Proceedings of the 6th International Symposium on Irrigation of Horticultural Crops
- Seite (von - bis)
- 1-5
- Tagungsname
- ISHS 6th International Symposium on Irrigation of Horticultural Crops
- Tagungsort
- Vina del Mar (Chile)
- Tagungsdatum
- 2. - 6.11.2009
The remote sensing of drought stress in plants is increasingly important in irrigation planning. Especially the use of thermal photography holds a big potential. However, the practical application is often limited by solid calibration data and exactly defined threshold values. These data is crop specific as the reaction to drought stress varies among different plant species.
In this study drought tolerant mango trees (Mangifera Indica, L.) and drought sensitive longan trees (Dimocarpus longan, Lour.) were submitted to a drying cycle under controlled conditions by complete withdrawal of irrigation water and compared to a well watered control. Drought stress reactions were monitored in terms of pre-dawn leaf water potential, stomatal resistance and change in soil water content. Trees were kept under shelter, so they were not exposed to direct radiation. Thermo images were taken every hour and the average canopy temperature was set into relation to wet and a dry reference to determine the threshold value for drought stress for both tree species. After establishment of drought stress, wind was applied at different levels and the changes in canopy temperature measured in a one-minute interval.
The temperature in the stress treatment changed quickly under the influence of wind. At a low wind speed there were still differences to the control visible. On the thermo images it was possible to determine the stressed treatment based on the changes in temperature of the reference surfaces. At higher levels of wind, the cooling effect was so strong that differences between treatment and control were not visible. It was shown that thermographic measurements for drought stress detection are very sensitive to wind. Even the use of reference surfaces does not enable the distinction between stressed and unstressed trees under influence of wind.