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A Step Towards Precision Irrigation: Plant Water Status Detection With Infrared Thermography
S. Zia

The increasing demand for water all over the world calls for precision agriculture which accounts globally about 70 percent of all water withdrawal. Therefore, there is a need to optimizing water use efficiency and making the best use of available water for irrigation. Plant water status detection for advanced irrigation scheduling is frequently done by predawn leaf water potential (ΨPD) or leaf stomata conductance (gL) measurements. However, these measurements are time and labour consuming. A non-invasive approach for water status detection is the use of infrared thermography (IRT). It visualizes the increase in leaf temperature as a consequence of the stomata closure when the plant is experiencing water stress due to the decrease in energy dissipation Therefore, IRT opens up the possibility to study large population of leaves and to give an overview on the stomatal variation and their dynamics. In the present study the possible use of IRT for identifying water stress is presented. The investigations were conducted in a greenhouse experiment on two potted maize genotypes having different drought susceptibility. Infrared pictures were made with Infratec Vario CAM. In addition, visible images were taken concurrently to identify the area of the leaves accurately. Vaseline covered leaf and tensiometer cup were used as dry and wet references respectively. The water status information deduced from infrared pictures was subsequently compared with gL and ΨPD that were simultaneously measured with SC-1 Porometer (Decagon Devices) and Scholander bomb, respectively. Associated meteorological data (relative humidity, temperature, solar radiation) were also measured. This method gives more accurate estimates of the temperature distribution of the canopy and makes it possible to quantify the relationship between temperature variation and stomatal conductance. The results show that the comparison of leaf temperature might be a further step towards irrigation scheduling with remote sensing.

Keyword: infrared thermography, leaf temperature, stomatal conductance, leaf water potential, plant water stress and maize