Application of infrared thermography technology for irrigation scheduling of winter wheat

摘要

Infrared thermography was used for winter wheat irrigation scheduling, because this method has advantages of non-contact, estimating large leave populations and saving human power, easy and fast. Measurements were taken under a range of environmental conditions by using infrared thermography to take thermal images of the winter wheat to acquire the temperatures of the canopy (Tcanopy) and its background, then testing the temperature of the reference leaves made by special methods to acquire two parameters, Twet and Tdry. According to former research, Crop Water Stress Index (CWSI) can be calculated through an empirical formula by utilizing Tcanopy, Twet and Tdry. CWSI has long been recognized as an indicator of plant water status and as a potential tool for irrigation scheduling. Because RGB color model used in the modern infrared thermography was designed to display different temperatures with different colors in these images, such relation with each others as: T=f (R, G, B); For getting more accurate temperature, firstly, utilizing image smoothing processing to reduce the influence of image noise. Secondly, highlight the desired part in the image of the winter wheat by color image enhancement; Then, taking the Twet and Tdry temperatures as threshold temperature to have color image segmentation for removing the color which represented the temperature of background such as soil and weed. After image processing, the image can be analyzed to give the average temperature of the real canopy to acquire the precise value of Tcanopy, then it'll be easy to obtain the right CWSI value. Comparing with the traditional method, this method has a high reliability to get CWSI. It's feasible to take infrared thermography as a tool for irrigation scheduling of winter wheat.