To achieve the overall goal, the proposed work consists of four major steps: 1) collecting aerial imagery using Small unmanned aircraft system (sUAS) platform on target plots for desired spatial resolution, image overlap, and altitude, 2) image analyzing using thermographic calibration curves compensating for environmental conditions during sensing campaigns, 3) image stitching (mosaicking) to create whole-plot spatial canopy temperature maps, and 4) measuring agronomic traits on a diverse range of soybean genotypes (including plant introductions and breeding lines). sUAS TIRIS has been developed at Biological and Agricultural Engineering department. It utilizes uncooled thermal camera and other required sensors for environmental compensation. Deployable temperature reference panels will be developed for in-flight accuracy assessment. These reference panels will be used to initialize and calibrate camera before, during, and after each flight. Multiple temperature reference panels will use thermistors connected to a data acquisition system (DAQ) to record real-time reference panel surface temperature while monitoring environmental parameters (i.e., air temperature, humidity, solar radiance, wind speed, and direction). As tested in full-season greenhouse corn studies last year, the TIRIS system will utilize calibration techniques using reference calibration images to quantify canopy temperatures from camera pixel intensity; corresponding transfer function from pixel intensity to surface temperatures along with camera sensor settings to accurately measure crop temperature profiles. In addition to thermal imaging, color infrared camera (CIR) mounted on the sUAS will be used to capture canopy reflectance. Ground reflectance reference panel will be used to calibrate CIR camera at the flying altitude.
TIRIS will be integrated with multi-rotor sUAS to collect aerial imagery. Test will be conducted at Kansas State University’s soybean breeding trials. A Certificate of Authorization (COA) for one year of flying sUAS for these locations will be obtained through K-State Saline Unmanned Aircraft Systems Program Office (USAPO). The research plots will consist of irrigated and dryland plots near Manhattan and Salina, Kansas. The target genotypes to be monitored will include lines that are under evaluation and development in the abiotic stress soybean breeding and genetics program pipeline. The sUAS with TIRIS will be flown at 15 and 25 m. Different heights are selected to understand and differentiate the effect of flying altitude on thermal imagery accuracy and image pixel degradation, dynamic accuracy of imaging system at different altitudes, pixel and canopy temperature resolution, assess productivity in terms acres covered per hour and assess economics of using this system. Nine airborne campaigns at each site will be conducted over the experimental plots to capture images around solar noon flight times to investigate the physiological status of the plant capturing the key flowering and seed-fill phases. In addition to aerial imagery, sampling regions will be randomly selected for ground truthing and; plant health and growth related data collected. Actual canopy temperature will be measured with leaf clip radiometers to validate aerial imagery results at selected sampling locations. Ground based evaluation of agronomic and physiological traits such as chlorophyll content using SPAD will be conducted for analysis and screening of drought resistant varieties. Plant material measurements will include seed yield, maturity, lodging, height and visual wilting scores. Potential effectiveness of this system to screen genotypes will be assessed by correlating thermal canopy profiles with relative seed yield, maturity and response to drought and heat stress.